View allAll Photos Tagged phytochemicals!
Iochroma is a genus of about 34 species of shrubs and small trees found in the forests of South America. They range from Colombia to Argentina or when certain species are excluded (see below) from Colombia to Peru. Their hummingbird-pollinated flowers are tubular or trumpet-shaped, and may be blue, purple, red, yellow, or white, becoming pulpy berries. The cupular calyx is inflated in some species. The leaves are alternate, simple, and entire.
Iochromas are cultivated as flowering ornamentals and in cooler zones (zones 7-8/9) make useful patio shrubs for summer display or conservatory plants. The majority are not frost hardy and must be overwintered under protection. In warmer zones (zones 9-10) they can be used as landscape plants. They are commonly trained as standards (topiary) to control their size and shape. Iochroma flowers attract hummingbirds (Americas only) and bees to gardens.
Like many plants in the Solanaceae, Iochroma species contain phytochemicals with potential pharmaceutical value but the genus has not been exhaustively studied in this respect. Iochroma fuchsioides is taken by the medicine men of the Kamsa Indians of the Sibundoy valley in the Colombian Andes for difficult diagnoses, the unpleasant side effects lasting several days (Schultes & Hoffman 1992). A variety of withanolides (Alfonso et al. 1993) and hydroxycinnamic acid amides (Sattar et al. 1990) have been isolated from Iochroma species.
The family Solanaceae is further divided into subfamilies, tribes and subtribes. Iochroma is in the subtribe Iochrominae along with the genera Acnistus, Dunalia, Eriolarynx, Saracha, and Vassobia.
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Baked reddish potatoes on an oven plate. All potatoes cut into halves. Shallow depth of filed. Light effect in the background.
Bituminaria bituminosa (L.) C. H. Stirt., syn.: Psoralea bituminosa L., Aspalthium bituminosum (L.) Fourr., Psoralea palaestina Gouan, Asphalthium bituminosum (L.) Medik.
Family: Fabaceae
EN: Arabian Pea, Pitch Trefoil, DE: Gewöhnlicher Asphaltklee
Slo.: arabski grah
Dat.: May 21. 2007
Lat.: 45,00508 Long.: 13,81403 WGS84
Code: Bot_0189/2007_DSC8001 and DSC8037, Bot_0190/2007_DSC8116, Bot_0191/2007_DSC8228
Habitat: Dry grassland with some bushes, flat terrain, open, sunny location; elevation 125 m (410 feet); average precipitations ~ 1.000 mm/year, average temperature 13-15 deg C, Sub-Mediterranean phytogeographical region.
Substratum: soil.
Place: Croatia, Istria peninsula, approximately 4.3 km south-southeast of Bale, east of the Bale-Pula road at the intersection of the local road leading to the village of Gajana.
Comment regarding the Flick album Bituminaria bituminosa: Bituminaria bituminosa is an intriguing and relatively uncommon Mediterranean plant. It is prevalent along the coasts of the Mediterranean Sea in all countries except Syria and Egypt. To the east, it extends as far as the Caucasus and the shores of the Black Sea (Ref.: 4).
Carl Linnaeus first formally described the plant as Psoralea bituminosa. A few years later, it was moved to the genus Bituminaria, which has experienced additional changes. Today, it resides again in the genus Bituminaria, which is relatively small—it includes only 10 species.
The species is easy to identify. If you slightly crush its leaves, they emit a distinct and unpleasant smell of tar. The plant has a fascinating phytochemical composition and exhibits potent antioxidant and antibacterial properties.
Ref.:
(1) T. Nikolić, Flora Croatica, Vaskularna flora Republike Hrvatske, Vol. 2., Alfa d.d.. Zagreb (2020), p 762.
(2) W.K. Rottensteiner, Exkursionsflora für Istrien, Verlag des Naturwissenschaftlichen Vereins Kärten (2014), p 447.
(3) M. Blamey, C. Grey-Wilson, Wild Flowers of the Mediterranean, A & C Black, London (2005), p 508.
(4) Euro+Med (2006+), Euro+Med PlantBase - the information resource for Euro-Mediterranean plant diversity. www.europlusmed.org [accessed March 3. 2025]
Exceed Plus! is a powerful blend of SUPERFOOD Turmeric and MIRACLE TREE – Moringa leaves in one capsule. It is loaded with phytochemicals that have essential impact on the health and wellness of an individual
RIUM, WP Kuala Lumpur, Malaysia.
Stemona curtisii Hook.f. Stemonaceae. CN; [Malay - Akar ratus, Akar seratus, Kemili hutan, Ubi kemili (sharing name with Plectranthus rotundifolius, a Lamiaceae), Pecah kelambu, Galak tua], Stemona. The vernacular names are often interchangeable used with Stemona tuberosa presumably non-native here and also many equally conflicting names and synonyms in various reports. Native to India (Nicobar Islands), Sri Lanka, Thailand and Malesia floristic zone. In peninsular Malaysia, occurrence is widespread, often in thickets near the sea, sometimes on limestone formations. Many scientific studies done to determine its phytochemical properties, but among the natives the root has been claimed an effective aphrodisiac.
Synonym(s):
Stemona minor Hook.f.
Ref. and suggested reading:
FRIM Flora Database
www.theplantlist.org/tpl/record/kew-288271
zipcodezoo.com/Plants/S/Stemona_curtisii/
proseanet.org/prosea/e-prosea_detail.php?frt=&id=1310
wannura.wordpress.com/2010/05/17/galak-tua-stemona-curtis...
Nước Chanh leo
•Nước ép từ chanh dây có tác dụng ngăn chặn sự phát triển của tế bào ung thư nhờ những chất hợp chất phytochemical tìm thấy trong cơm quả. Các axít phenolic và flavonoid có tác dụng ngăn ngừa bệnh tim mạch và chống nhiễm trùng. Các chất tan trong nước cũng như tan trong dầu đều có tác dụng chống oxy hoá tế bào, tăng cường miễn dịch, chống lão hoá.
•Chanh dây chứa nhiều loại đường đơn, giúp tăng cường thể lực nhưng không hại cho người tiểu đường.
• Chanh dây là một nguồn vitamin và chất xơ nên giúp gia tăng sức khoẻ mà không gây béo phì. Chanh dây có chứa hợp chất sterol thực vật nên không làm tăng cholesterol trong máu.
Dahlia (UK /deɪliə/ or US /dɑːliə/) is a genus of bushy, tuberous, herbaceous perennial plants native to Mexico. A member of the Asteraceae (or Compositae), dicotyledonous plants, related species include the sunflower, daisy, chrysanthemum, and zinnia. There are 42 species of dahlia, with hybrids commonly grown as garden plants. Flower forms are variable, with one head per stem; these can be as small as 5.1 cm diameter or up to 30 cm ("dinner plate"). This great variety results from dahlias being octoploids—that is, they have eight sets of homologous chromosomes, whereas most plants have only two. In addition, dahlias also contain many transposons - genetic pieces that move from place to place upon an allele - which contributes to their manifesting such great diversity.
The stems are leafy, ranging in height from as low as 30 cm to more than 1.8–2.4 m. The majority of species do not produce scented flowers or cultivars. Like most plants that do not attract pollinating insects through scent, they are brightly colored, displaying most hues, with the exception of blue.
The dahlia was declared the national flower of Mexico in 1963. The tubers were grown as a food crop by the Aztecs, but this use largely died out after the Spanish Conquest. Attempts to introduce the tubers as a food crop in Europe were unsuccessful.
DESCRIPTION
Perennial plants, with mostly tuberous roots. While some have herbaceous stems, others have stems which lignify in the absence of secondary tissue and resprout following winter dormancy, allowing further seasons of growth. as a member of the Asteraceae the flower head is actually a composite (hence the older name Compositae) with both central disc florets and surrounding ray florets. Each floret is a flower in its own right, but is often incorrectly described as a petal, particularly by horticulturalists. The modern mame Asteraceae refers to the appearance of a star with surrounding rays.
TAXONOMY
HISTORY
EARLY HISTORY
Spaniards reported finding the plants growing in Mexico in 1525, but the earliest known description is by Francisco Hernández, physician to Philip II, who was ordered to visit Mexico in 1570 to study the "natural products of that country". They were used as a source of food by the indigenous peoples, and were both gathered in the wild and cultivated. The Aztecs used them to treat epilepsy, and employed the long hollow stem of the (Dahlia imperalis) for water pipes. The indigenous peoples variously identified the plants as "Chichipatl" (Toltecs) and "Acocotle" or "Cocoxochitl" (Aztecs). From Hernandez' perception of Aztec, to Spanish, through various other translations, the word is "water cane", "water pipe", "water pipe flower", "hollow stem flower" and "cane flower". All these refer to the hollowness of the plants' stem.Hernandez described two varieties of dahlias (the pinwheel-like Dahlia pinnata and the huge Dahlia imperialis) as well as other medicinal plants of New Spain. Francisco Dominguez, a Hidalgo gentleman who accompanied Hernandez on part of his seven-year study, made a series of drawings to supplement the four volume report. Three of his drawings showed plants with flowers: two resembled the modern bedding dahlia, and one resembled the species Dahlia merki; all displayed a high degree of doubleness. In 1578 the manuscript, entitled Nova Plantarum, Animalium et Mineralium Mexicanorum Historia, was sent back to the Escorial in Madrid; they were not translated into Latin by Francisco Ximenes until 1615. In 1640, Francisco Cesi, President of the Academia Linei of Rome, bought the Ximenes translation, and after annotating it, published it in 1649-1651 in two volumes as Rerum Medicarum Novae Hispaniae Thesaurus Seu Nova Plantarium, Animalium et Mineraliuím Mexicanorum Historia. The original manuscripts were destroyed in a fire in the mid-1600s.
EUROPEAN INTRODUCTION
In 1787, the French botanist Nicolas-Joseph Thiéry de Menonville, sent to Mexico to steal the cochineal insect valued for its scarlet dye, reported the strangely beautiful flowers he had seen growing in a garden in Oaxaca. In 1789, Vicente Cervantes, Director of the Botanical Garden at Mexico City, sent "plant parts" to Abbe Antonio José Cavanilles, Director of the Royal Gardens of Madrid. Cavanilles flowered one plant that same year, then the second one a year later. In 1791 he called the new growths "Dahlia" for Anders Dahl. The first plant was called Dahlia pinnata after its pinnate foliage; the second, Dahlia rosea for its rose-purple color. In 1796 Cavanilles flowered a third plant from the parts sent by Cervantes, which he named Dahlia coccinea for its scarlet color.In 1798, Cavanilles sent D. Pinnata seeds to Parma, Italy. That year, the Marchioness of Bute, wife of The Earl of Bute, the English Ambassador to Spain, obtained a few seeds from Cavanilles and sent them to Kew Gardens, where they flowered but were lost after two to three years. In the following years Madrid sent seeds to Berlin and Dresden in Germany, and to Turin and Thiene in Italy. In 1802, Cavanilles sent tubers of "these three" (D. pinnata, D. rosea, D. coccinea) to Swiss botanist Augustin Pyramus de Candolle at University of Montpelier in France, Andre Thouin at the Jardin des Plantes in Paris and Scottish botanist William Aiton at Kew Gardens. That same year, John Fraser, English nurseryman and later botanical collector to the Czar of Russia, brought D. coccinea seeds from Paris to the Apothecaries Gardens in England, where they flowered in his greenhouse a year later, providing Botanical Magazine with an illustration.In 1804, a new species, Dahlia sambucifolia, was successfully grown at Holland House, Kensington. Whilst in Madrid in 1804, Lady Holland was given either dahlia seeds or tubers by Cavanilles. She sent them back to England, to Lord Holland's librarian Mr Buonaiuti at Holland House, who successfully raised the plants. A year later, Buonaiuti produced two double flowers. The plants raised in 1804 did not survive; new stock was brought from France in 1815. In 1824, Lord Holland sent his wife a note containing the following verse:
"The dahlia you brought to our isle
Your praises for ever shall speak;
Mid gardens as sweet as your smile,
And in colour as bright as your cheek."
In 1805, German naturalist Alexander von Humboldt sent more seeds from Mexico to Aiton in England, Thouin in Paris, and Christoph Friedrich Otto, director of the Berlin Botanical Garden. More significantly, he sent seeds to botanist Carl Ludwig Willdenow in Germany. Willdenow now reclassified the rapidly growing number of species, changing the genus from Dahlia to Georgina; after naturalist Johann Gottlieb Georgi. He combined the Cavanilles species D. pinnata and D. rosea under the name of Georgina variabilis; D. coccinea was still held to be a separate species, which he renamed Georgina coccinea.
CLASSIFICATION
Since 1789 when Cavanilles first flowered the dahlia in Europe, there has been an ongoing effort by many growers, botanists and taxonomists, to determine the development of the dahlia to modern times. At least 85 species have been reported: approximately 25 of these were first reported from the wild, the remainder appeared in gardens in Europe. They were considered hybrids, the results of crossing between previously reported species, or developed from the seeds sent by Humboldt from Mexico in 1805, or perhaps from some other undocumented seeds that had found their way to Europe. Several of these were soon discovered to be identical with earlier reported species, but the greatest number are new varieties. Morphological variation is highly pronounced in the dahlia. William John Cooper Lawrence, who hybridized hundreds of families of dahlias in the 1920s, stated: "I have not yet seen any two plants in the families I have raised which were not to be distinguished one from the other. Constant reclassification of the 85 reported species has resulted in a considerably smaller number of distinct species, as there is a great deal of disagreement today between systematists over classification.
In 1829, all species growing in Europe were reclassified under an all-encompassing name of D. variabilis, Desf., though this is not an accepted name. Through the interspecies cross of the Humboldt seeds and the Cavanilles species, 22 new species were reported by that year, all of which had been classified in different ways by several different taxonomists, creating considerable confusion as to which species was which.
In 1830 William Smith suggested that all dahlia species could be divided into two groups for color, red-tinged and purple-tinged. In investigating this idea Lawrence determined that with the exception of D. variabilis, all dahlia species may be assigned to one of two groups for flower-colour: Group I (ivory-magenta) or Group II (yellow-orange-scarlet).
CIRCUMSCRIPTION
The genus Dahlia is situated in the Asteroideae subfamily of the Asteraceae, in the Coreopsideae tribe. Within that tribe it is the second largest genus, after Coreopsis, and appears as a well defined clade within the Coreopsideae.
SUBDIVISION
INFRAGENERIC SUBDIVISION
Sherff (1955), in the first modern taxonomy described three sections for the 18 species he recognised, Pseudodendron, Epiphytum and Dahlia. By 1969 Sørensen recognised 29 species and four sections by splitting off Entemophyllon from section Dahlia. By contrast Giannasi (1975) using a phytochemical analysis based on flavonoids, reduced the genus to just two sections, Entemophyllon and Dahlia, the latter having three subsections, Pseudodendron, Dahlia, and Merckii. Sørensen then issued a further revision in 1980, incorporating subsection Merckii in his original section Dahlia. When he described two new species in the 1980s (Dahlia tubulata and D. congestifolia), he placed them within his existing sections. A further species, Dahlia sorensenii was added by Hansen and Hjerting in (1996). At the same time they demonstrated that Dahlia pinnata should more properly be designated D. x pinnata. D. x pinnata was shown to actually be a variant of D. sorensenii that had acquired hybrid qualities before it was introduced to Europe in the sixteenth century and formally named by Cavanilles. The original wild D. pinnata is presumed extinct. Further species continue to be described, Saar (2003) describing 35 species. However separation of the sections on morphological, cytologal and biocemical criteria has not been entirely satisfactory.
To date these sectional divisions have not been fully supported phylogenetically, which demonstrate only section Entemophyllon as a distinct sectional clade. The other major grouping is the Core Dahlia Clade (CDC), which includes most of section Dahlia. The remainder of the species occupy what has been described as the Variable Root Clade (VRC) which includes the small section Pseudodendron but also the monotypic section Epiphytum and a number of species from within section Dahlia. Outside of these three clades lie D. tubulata and D. merckii as a polytomy.
Horticulturally the sections retain some usage, section Pseudodendron being referred to as 'Tree Dahlias', Epiphytum as the 'Vine Dahlia'. The remaining two herbaceous sections being distinguished by their pinnules, opposing (Dahlia) or alternating (Entemophyllon).
SECTIONS
Sections (including chromosome numbers), with geographical distribution;
- Epiphytum Sherff (2n = 32)
10 m tall climber with aerial roots 5 cm thick and up to more than 20 m long; pinnules opposite
1 species, D. macdougallii Sherff
Mexico: Oaxaca
- Entemophyllon P. D. Sorensen (2n = 34)
6 species
Mexico: Hidalgo, Nuevo León, Tamaulipas, Querétaro, Durango, San Luis Potosí
- Pseudodendron P. D. Sorensen (2n = 32)
3 species + D. excelsa of uncertain identity
Mexico: Chiapas, Guerrero, Jalisco, Michoacan, Oaxaca, and
Costa Rica, El Salvador, Guatemala & Colombia
- Dahlia (2n = 32, 36 or 64)
24 species
Mexico: Distrito Federal, Guerrero, Hidalgo, Morelos, Nuevo León, Puebla, San Luis Potosí, Tamaulipas, Veracruz, Oaxaca, Puebla, Chiapas, México, Huehuetenango, Chihuahua, Durango, Michoacan & Guatemala
Only Pseudodendron (D. imperialis) and Dahlia (D. australis, D. coccinea) occur outside Mexico.
SPECIES
There are currently 42 accepted species in the Dahlia genus, but new species continue to be described.
ETYMOLOGY
The naming of the plant itself has long been a subject of some confusion. Many sources state that the name "Dahlia" was bestowed by the pioneering Swedish botanist and taxonomist Carl Linnaeus to honor his late student, Anders Dahl, author of Observationes Botanicae. However, Linnaeus died in 1778, more than eleven years before the plant was introduced into Europe in 1789, so while it is generally agreed that the plant was named in 1791 in honor of Dahl, who had died two years before, Linnaeus could not have been the one who did so. It was probably Abbe Antonio Jose Cavanilles, Director of the Royal Gardens of Madrid, who should be credited with the attempt to scientifically define the genus, since he not only received the first specimens from Mexico in 1789, but named the first three species that flowered from the cuttings.
Regardless of who bestowed it, the name was not so easily established. In 1805, German botanist Carl Ludwig Willdenow, asserting that the genus Dahlia Thunb. (published a year after Cavanilles's genus and now considered a synonym of Trichocladus) was more widely accepted, changed the plants' genus from Dahlia to Georgina; after the German-born naturalist Johann Gottlieb Georgi, a professor at the Imperial Academy of Sciences of St. Petersburg, Russia. He also reclassified and renamed the first three species grown, and identified, by Cavanilles. It was not until 1810, in a published article, that he officially adopted the Cavanilles' original designation of Dahlia. However, the name Georgina still persisted in Germany for the next few decades.
"Dahl" is a homophone of the Swedish word "dal", or "valley"; although it is not a true translation, the plant is sometimes referred to as the "valley flower".
DISTRIBUTION AND HABITAT
Predominantly Mexico, but some species are found ranging as far south as northern South America. D. australis occurs at least as far south as southwestern Guatemala, while D. coccinea and D. imperialis also occur in parts of Central America and northern South America. Dahlia is a genus of the uplands and mountains, being found at elevations between 1,500 and 3,700 meters, in what has been described as a "pine-oak woodland" vegetative zone. Most species have limited ranges scattered throughout many mountain ranges in Mexico.
ECOLOGY
The commonest pollinators are bees and small beetles.
PESTS AND DISEASES
Slugs and snails are serious pests in some parts of the world, particularly in spring when new growth is emerging through the soil. Earwigs can also disfigure the blooms. The other main pests likely to be encountered are aphids (usually on young stems and immature flower buds), red spider mite (causing foliage mottling and discolouration, worse in hot and dry conditions) and capsid bugs (resulting in contortion and holes at growing tips). Diseases affecting dahlias include powdery mildew, grey mould (Botrytis cinerea), verticillium wilt, dahlia smut (Entyloma calendulae f. dahliae), phytophthora and some plant viruses. Dahlias are a source of food for the larvae of some Lepidoptera species including Angle Shades, Common Swift, Ghost Moth and Large Yellow Underwing.
CULTIVATION
Dahlias grow naturally in climates which do not experience frost (the tubers are hardy to USDA Zone 8), consequently they are not adapted to withstand sub-zero temperatures. However, their tuberous nature enables them to survive periods of dormancy, and this characteristic means that gardeners in temperate climates with frosts can grow dahlias successfully, provided the tubers are lifted from the ground and stored in cool yet frost-free conditions during the winter. Planting the tubers quite deep (10 – 15 cm) also provides some protection. When in active growth, modern dahlia hybrids perform most successfully in well-watered yet free-draining soils, in situations receiving plenty of sunlight. Taller cultivars usually require some form of staking as they grow, and all garden dahlias need deadheading regularly, once flowering commences.
HORTICURAL CLASSIFICATION
HISTORY
The inappropriate term D. variabilis is often used to describe the cultivars of Dahlia since the correct parentage remains obscure, but probably involves Dahlia coccinea. In 1846 the Caledonia Horticultural Society of Edinburgh offered a prize of 2,000 pounds to the first person succeeding in producing a blue dahlia. This has to date not been accomplished. While dahlias produce anthocyanin, an element necessary for the production of the blue, to achieve a true blue color in a plant, the anthocyanin delphinidin needs six hydroxyl groups. To date dahlias have only developed five, so the closest that breeders have come to achieving a "blue" specimen are variations of mauve, purples and lilac hues.
By the beginning of the twentieth century a number of different types were recognised. These terms were based on shape or colour, and the National Dahlia Society included cactus, pompon, single, show and fancy in its 1904 guide. Many national societies developed their own classification systems until 1962 when the International Horticultural Congress agreed to develop an internationally recognised system at it Brussels meeting that year, and subsequently in Maryland in 1966. This culminated in the 1969 publication of The International Register of Dahlia Names by the Royal Horticultural Society which became the central registering authority.
This system depended primarily on the visibility of the central disc, whether it was open centred or whether only ray florets were apparent centrally (double bloom). The double bloom cultivars were then subdivided according to the way in which they were folded along their longitudinal axis, flat, involute (curled inwards) or revolute (curling backwards). If the end of the ray floret was split, they were considered fimbriated. Based on these characteristics, nine groups were defined plua a tenth miscellaneous group for any cultivars not fitting the above characteristics. Fimbriated dahlias were added in 2004, and two further groups (Single and Double orchid) in 2007. The last group to be added, Peony, first appeared in 2012.
In many cases the bloom diametre was then used to further label certain groups from miniature through to giant. This practice was abandoned in 2012.
MODERN SYSTEM (RHS)
There are now more than 57,000 registered cultivars, which are officially registered through the Royal Horticultural Society (RHS). The official register is The International Register of Dahlia Names 1969 (1995 reprint) which is updated by annual supplements. The original 1969 registry published about 14,000 cultivars adding a further 1700 by 1986 and in 2003 there were 18,000. Since then about a hundred new cultivars are added annually.
FLOWER TYPE
The official RHS classification lists fourteen groups, grouped by flower type, together with the abbreviations used by the RHS;
Group 1 – Single-flowered dahlias (Sin) — Flower has a central disc with a single outer ring of florets (which may overlap) encircling it, and which may be rounded or pointed.
Group 2 – Anemone-flowered dahlias (Anem) — The centre of the flower consists of dense elongated tubular florets, longer than the disc florets of Single dahlias, while the outer parts have one or more rings of flatter ray florets. Disc absent.
Group 3 – Collerette dahlias (Col) — Large flat florets forming a single outer ring around a central disc and which may overlap a smaller circle of florets closer to the centre, which have the appearance of a collar.
Group 4 – Waterlily dahlias (WL) — Double blooms, broad sparse curved, slightly curved or flat florets and very shallow in depth compared with other dahlias. Depth less than half the diameter of the bloom. Group 5 – Decorative dahlias (D) — Double blooms, ray florets broad, flat, involute no more than seventy five per cent of the longitudinal axis, slightly twisted and usually bluntly pointed. No visible central disc.
Group 6 – Ball dahlias (Ba)— Double blooms that are ball shaped or slightly flattened. Ray florets blunt or rounded at the tips, margins arranged spirally, involute for at least seventy five percent of the length of the florets. Larger than Pompons.
Group 7 – Pompon dahlias (Pom) — Double spherical miniature flowers made up entirely from florets that are curved inwards (involute) for their entire length (longitudinal axis), resembling a pompon.
Group 8 – Cactus dahlias (C) — Double blooms, ray florets pointed, with majority revolute (rolled) over more than fifty percent of their longitudinal axis, and straight or incurved. Narrower than Semi cactus.
Group 9 – Semi cactus dahlias (S–c)— Double blooms, very pointed ray florets, revolute for greater than twenty five percent and less than fifty percent of their longitudinal axis. Broad at the base and straight or incurved, almost spiky in appearance.
Group 10 – Miscellaneous dahlias (Misc) — not described in any other group.
Group 11 – Fimbriated dahlias (Fim) — ray florets evenly split or notched into two or more divisions, uniformly throughout the bloom, creating a fimbriated (fringed) effect. The petals may be flat, involute, revolute, straight, incurving or twisted.
Group 12 – Single Orchid (Star) dahlias (SinO) — single outer ring of florets surround a central disc. The ray florets are either involute or revolute.
Group 13 – Double Orchid dahlias (DblO) — Double blooms with triangular centres. The ray florets are narrowly lanceolate and are either involute or revolute. The central disc is absent.
Group 14 – Peony-flowered dahlias (P) — Large flowers with three or four rows of rays that are flattened and expanded and arranged irregularly. The rays surround a golden disc similar to that of Single dahlias.
FLOWER SIZE
Earlier versions of the registry subdivided some groups by flower size. Groups 4, 5, 8 and 9 were divided into five subgroups (A to E) from Giant to Miniature, and Group 6 into two subgroups, Small and Miniature. Dahlias were then described by Group and Subgroup, e.g. 5(d) ‘Ace Summer Sunset’. Some Dahlia Societies have continued this practice, but this is neither official nor standardised. As of 2013 The RHS uses two size descriptors
Dwarf Bedder (Dw.B.) — not usually exceeding 600 mm in height, e.g. 'Preston Park' (Sin/DwB)
Lilliput dahlias (Lil) — not usually exceeding 300 mm in height, with single, semi-double or double florets up to 26 mm in diameter. ("baby" or "top-mix" dahlias), e.g. 'Harvest Tiny Tot' (Misc/Lil)
Sizes can range from tiny micro dahlias with flowers less than 50mm to giants that are over 250mm in diameter. The groupings listed here are from the New Zealand Society.
Giant flowered cultivars have blooms with a diameter of over 250mm.
Large flowered cultivars have blooms with a diameter between 200mm-250mm.
Medium flowered cultivars have blooms with a diameter between 155mm-200mm.
Small flowered cultivars have blooms with a diameter between 115mm-155mm.
Miniature flowered cultivars have blooms with a diameter between 50mm-115mm.
Pompom flowered cultivars have blooms with a diameter less than 50mm.
In addition to the official classification and the terminology used by various dahlia societies, individual horticulturalists use a wide range of other descriptions, such as 'Incurved' and abbreviations in their catalogues, such as CO for Collarette.
BRANDING
Some plant growers include their brand name in the cultivar name. Thus Fides (part of the Dümmen Orange Group) in the Netherlands developed a series of cultivars which they named the Dahlinova Series, for example Dahlinova 'Carolina Burgundy'. These are Group 10 Miscellaneous in the RHS classification scheme.
DOUBLE DAHLIAS
In 1805, several new species were reported with red, purple, lilac, and pale yellow coloring, and the first true double flower was produced in Belgium. One of the more popular concepts of dahlia history, and the basis for many different interpretations and confusion, is that all the original discoveries were single flowered types, which, through hybridization and selective breeding, produced double forms. Many of the species of dahlias then, and now, have single flowered blooms. coccinea, the third dahlia to bloom in Europe, was a single. But two of the three drawings of dahlias by Dominguez, made in Mexico between 1570–77, showed definite characteristics of doubling. In the early days of the dahlia in Europe, the word "double" simply designated flowers with more than one row of petals. The greatest effort was now directed to developing improved types of double dahlias.
During the years 1805 to 1810 several people claimed to have produced a double dahlia. In 1805 Henry C. Andrews made a drawing of such a plant in the collection of Lady Holland, grown from seedlings sent that year from Madrid. Like other doubles of the time it did not resemble the doubles of today. The first modern double, or full double, appeared in Belgium; M. Donckelaar, Director of the Botanic Garden at Louvain, selected plants for that characteristic, and within a few years secured three fully double forms. By 1826 double varieties were being grown almost exclusively, and there was very little interest in the single forms. Up to this time all the so-called double dahlias had been purple, or tinged with purple, and it was doubted if a variety untinged with that color was obtainable.
In 1843, scented single forms of dahlias were first reported in Neu Verbass, Austria. D. crocea, a fragrant variety grown from one of the Humboldt seeds, was probably interbred with the single D. coccinea. A new scented species would not be introduced until the next century when the D. coronata was brought from Mexico to Germany in 1907.
The exact date the dahlia was introduced in the United States is uncertain. One of the first Dahlias in the USA may be the D. coccinea speciosissima grown by Mr William Leathe, of Cambridgeport, near Boston, around 1929. According to Edward Sayers "it attracted much admiration, and at that time was considered a very elegant flower, it was however soon eclipsed by that splendid scarlet, the Countess of Liverpool". However 9 cultivars were already listed in the catalog from Thornburn, 1825. And even earlier reference can be found in a catalogue from the Linnaean Botanical Garden, New York, 1820, that includes one scarlet, one purple, and two double orange Dahlias for sale.
Sayers stated that "No person has done more for the introduction and advancement of the culture of the Dahlia than George C. Thorburn, of New York, who yearly flowers many thousand plants at his place at Hallet's Cove, near Harlaem. The show there in the flowering season is a rich treat for the lovers of floriculture : for almost every variety can be seen growing in two large blocks or masses which lead from the road to the dwelling-house, and form a complete field of the Dahlia as a foreground to the house. Mr T. Hogg, Mr William Read, and many other well known florists, have also contributed much in the vicinity of New York, to the introduction of the Dahlia. Indeed so general has become the taste that almost every garden has its show of the Dahlia in the season." In Boston too there were many collections, a collection from the Messrs Hovey of Cambridgeport was also mentioned.
In 1835 Thomas Bridgeman, published a list of 160 double dahlias in his Florist's Guide. 60 of the choicest were supplied by Mr. G. C. Thornburn of Astoria, N.Y. who got most of them from contacts in the UK. Not a few of them had taken prices "at the English and American exhibitions".
"STARS OF DEVIL"
In 1872 J.T. van der Berg of Utrecht in the Netherlands, received a shipment of seeds and plants from a friend in Mexico. The entire shipment was badly rotted and appeared to be ruined, but van der Berg examined it carefully and found a small piece of root that seemed alive. He planted and carefully tended it; it grew into a plant that he identified as a dahlia. He made cuttings from the plant during the winter of 1872-1873. This was an entirely different type of flower, with a rich, red color and a high degree of doubling. In 1874 van der Berg catalogued it for sale, calling it Dahlia juarezii to honor Mexican President Benito Pablo Juarez, who had died the year before, and described it as "...equal to the beautiful color of the red poppy. Its form is very outstanding and different in every respect of all known dahlia flowers.".
This plant has perhaps had a greater influence on the popularity of the modern dahlia than any other. Called "Les Etoiles de Diable" (Stars of the Devil) in France and "Cactus dahlia" elsewhere, the edges of its petals rolled backwards, rather than forward, and this new form revolutionized the dahlia world. It was thought to be a distinct mutation since no other plant that resembled it could be found in the wild. Today it is assumed that D. juarezii had, at one time, existed in Mexico and subsequently disappeared. Nurserymen in Europe crossbred this plant with dahlias discovered earlier; the results became the progenitors of all modern dahlia hybrids today.
AWARD OF GARDEN MERIT (RHS)
As of 2015, 124 dahlia cultivars have gained the Royal Horticultural Society's Award of Garden Merit:
"Bednall beauty"
"Bishop of Llandaff"
"Clair de lune"
"David Howard"
"Ellen Huston"
"Fascination"
"Gallery art deco"
"Gallery Art Nouveau"
"Glorie van Heemstede"
"Honka"
"Moonfire"
"Twyning's After Eight"
USES
FLORICULTURE
The asterid eudicots contain two economically important geophyte genera, Dahlia and Liatris. Horticulturally the garden dahlia is usually treated as the cultigen D. variabilis Hort., which while being responsible for thousands of cultivars has an obscure taxonomic status.
OTHER
Today the dahlia is still considered one of the native ingredients in Oaxacan cuisine; several cultivars are still grown especially for their large, sweet potato-like tubers. Dacopa, an intense mocha-tasting extract from the roasted tubers, is used to flavor beverages throughout Central America.
In Europe and America, prior to the discovery of insulin in 1923, diabetics - as well as consumptives - were often given a substance called Atlantic starch or diabetic sugar, derived from inulin, a naturally occurring form of fruit sugar, extracted from dahlia tubers. Inulin is still used in clinical tests for kidney functionality.
WIKIPEDIA
Dahlia (UK /deɪliə/ or US /dɑːliə/) is a genus of bushy, tuberous, herbaceous perennial plants native to Mexico. A member of the Asteraceae (or Compositae), dicotyledonous plants, related species include the sunflower, daisy, chrysanthemum, and zinnia. There are 42 species of dahlia, with hybrids commonly grown as garden plants. Flower forms are variable, with one head per stem; these can be as small as 5.1 cm diameter or up to 30 cm ("dinner plate"). This great variety results from dahlias being octoploids—that is, they have eight sets of homologous chromosomes, whereas most plants have only two. In addition, dahlias also contain many transposons - genetic pieces that move from place to place upon an allele - which contributes to their manifesting such great diversity.
The stems are leafy, ranging in height from as low as 30 cm to more than 1.8–2.4 m. The majority of species do not produce scented flowers or cultivars. Like most plants that do not attract pollinating insects through scent, they are brightly colored, displaying most hues, with the exception of blue.
The dahlia was declared the national flower of Mexico in 1963. The tubers were grown as a food crop by the Aztecs, but this use largely died out after the Spanish Conquest. Attempts to introduce the tubers as a food crop in Europe were unsuccessful.
DESCRIPTION
Perennial plants, with mostly tuberous roots. While some have herbaceous stems, others have stems which lignify in the absence of secondary tissue and resprout following winter dormancy, allowing further seasons of growth. as a member of the Asteraceae the flower head is actually a composite (hence the older name Compositae) with both central disc florets and surrounding ray florets. Each floret is a flower in its own right, but is often incorrectly described as a petal, particularly by horticulturalists. The modern mame Asteraceae refers to the appearance of a star with surrounding rays.
TAXONOMY
HISTORY
EARLY HISTORY
Spaniards reported finding the plants growing in Mexico in 1525, but the earliest known description is by Francisco Hernández, physician to Philip II, who was ordered to visit Mexico in 1570 to study the "natural products of that country". They were used as a source of food by the indigenous peoples, and were both gathered in the wild and cultivated. The Aztecs used them to treat epilepsy, and employed the long hollow stem of the (Dahlia imperalis) for water pipes. The indigenous peoples variously identified the plants as "Chichipatl" (Toltecs) and "Acocotle" or "Cocoxochitl" (Aztecs). From Hernandez' perception of Aztec, to Spanish, through various other translations, the word is "water cane", "water pipe", "water pipe flower", "hollow stem flower" and "cane flower". All these refer to the hollowness of the plants' stem.Hernandez described two varieties of dahlias (the pinwheel-like Dahlia pinnata and the huge Dahlia imperialis) as well as other medicinal plants of New Spain. Francisco Dominguez, a Hidalgo gentleman who accompanied Hernandez on part of his seven-year study, made a series of drawings to supplement the four volume report. Three of his drawings showed plants with flowers: two resembled the modern bedding dahlia, and one resembled the species Dahlia merki; all displayed a high degree of doubleness. In 1578 the manuscript, entitled Nova Plantarum, Animalium et Mineralium Mexicanorum Historia, was sent back to the Escorial in Madrid; they were not translated into Latin by Francisco Ximenes until 1615. In 1640, Francisco Cesi, President of the Academia Linei of Rome, bought the Ximenes translation, and after annotating it, published it in 1649-1651 in two volumes as Rerum Medicarum Novae Hispaniae Thesaurus Seu Nova Plantarium, Animalium et Mineraliuím Mexicanorum Historia. The original manuscripts were destroyed in a fire in the mid-1600s.
EUROPEAN INTRODUCTION
In 1787, the French botanist Nicolas-Joseph Thiéry de Menonville, sent to Mexico to steal the cochineal insect valued for its scarlet dye, reported the strangely beautiful flowers he had seen growing in a garden in Oaxaca. In 1789, Vicente Cervantes, Director of the Botanical Garden at Mexico City, sent "plant parts" to Abbe Antonio José Cavanilles, Director of the Royal Gardens of Madrid. Cavanilles flowered one plant that same year, then the second one a year later. In 1791 he called the new growths "Dahlia" for Anders Dahl. The first plant was called Dahlia pinnata after its pinnate foliage; the second, Dahlia rosea for its rose-purple color. In 1796 Cavanilles flowered a third plant from the parts sent by Cervantes, which he named Dahlia coccinea for its scarlet color.In 1798, Cavanilles sent D. Pinnata seeds to Parma, Italy. That year, the Marchioness of Bute, wife of The Earl of Bute, the English Ambassador to Spain, obtained a few seeds from Cavanilles and sent them to Kew Gardens, where they flowered but were lost after two to three years. In the following years Madrid sent seeds to Berlin and Dresden in Germany, and to Turin and Thiene in Italy. In 1802, Cavanilles sent tubers of "these three" (D. pinnata, D. rosea, D. coccinea) to Swiss botanist Augustin Pyramus de Candolle at University of Montpelier in France, Andre Thouin at the Jardin des Plantes in Paris and Scottish botanist William Aiton at Kew Gardens. That same year, John Fraser, English nurseryman and later botanical collector to the Czar of Russia, brought D. coccinea seeds from Paris to the Apothecaries Gardens in England, where they flowered in his greenhouse a year later, providing Botanical Magazine with an illustration.In 1804, a new species, Dahlia sambucifolia, was successfully grown at Holland House, Kensington. Whilst in Madrid in 1804, Lady Holland was given either dahlia seeds or tubers by Cavanilles. She sent them back to England, to Lord Holland's librarian Mr Buonaiuti at Holland House, who successfully raised the plants. A year later, Buonaiuti produced two double flowers. The plants raised in 1804 did not survive; new stock was brought from France in 1815. In 1824, Lord Holland sent his wife a note containing the following verse:
"The dahlia you brought to our isle
Your praises for ever shall speak;
Mid gardens as sweet as your smile,
And in colour as bright as your cheek."
In 1805, German naturalist Alexander von Humboldt sent more seeds from Mexico to Aiton in England, Thouin in Paris, and Christoph Friedrich Otto, director of the Berlin Botanical Garden. More significantly, he sent seeds to botanist Carl Ludwig Willdenow in Germany. Willdenow now reclassified the rapidly growing number of species, changing the genus from Dahlia to Georgina; after naturalist Johann Gottlieb Georgi. He combined the Cavanilles species D. pinnata and D. rosea under the name of Georgina variabilis; D. coccinea was still held to be a separate species, which he renamed Georgina coccinea.
CLASSIFICATION
Since 1789 when Cavanilles first flowered the dahlia in Europe, there has been an ongoing effort by many growers, botanists and taxonomists, to determine the development of the dahlia to modern times. At least 85 species have been reported: approximately 25 of these were first reported from the wild, the remainder appeared in gardens in Europe. They were considered hybrids, the results of crossing between previously reported species, or developed from the seeds sent by Humboldt from Mexico in 1805, or perhaps from some other undocumented seeds that had found their way to Europe. Several of these were soon discovered to be identical with earlier reported species, but the greatest number are new varieties. Morphological variation is highly pronounced in the dahlia. William John Cooper Lawrence, who hybridized hundreds of families of dahlias in the 1920s, stated: "I have not yet seen any two plants in the families I have raised which were not to be distinguished one from the other. Constant reclassification of the 85 reported species has resulted in a considerably smaller number of distinct species, as there is a great deal of disagreement today between systematists over classification.
In 1829, all species growing in Europe were reclassified under an all-encompassing name of D. variabilis, Desf., though this is not an accepted name. Through the interspecies cross of the Humboldt seeds and the Cavanilles species, 22 new species were reported by that year, all of which had been classified in different ways by several different taxonomists, creating considerable confusion as to which species was which.
In 1830 William Smith suggested that all dahlia species could be divided into two groups for color, red-tinged and purple-tinged. In investigating this idea Lawrence determined that with the exception of D. variabilis, all dahlia species may be assigned to one of two groups for flower-colour: Group I (ivory-magenta) or Group II (yellow-orange-scarlet).
CIRCUMSCRIPTION
The genus Dahlia is situated in the Asteroideae subfamily of the Asteraceae, in the Coreopsideae tribe. Within that tribe it is the second largest genus, after Coreopsis, and appears as a well defined clade within the Coreopsideae.
SUBDIVISION
INFRAGENERIC SUBDIVISION
Sherff (1955), in the first modern taxonomy described three sections for the 18 species he recognised, Pseudodendron, Epiphytum and Dahlia. By 1969 Sørensen recognised 29 species and four sections by splitting off Entemophyllon from section Dahlia. By contrast Giannasi (1975) using a phytochemical analysis based on flavonoids, reduced the genus to just two sections, Entemophyllon and Dahlia, the latter having three subsections, Pseudodendron, Dahlia, and Merckii. Sørensen then issued a further revision in 1980, incorporating subsection Merckii in his original section Dahlia. When he described two new species in the 1980s (Dahlia tubulata and D. congestifolia), he placed them within his existing sections. A further species, Dahlia sorensenii was added by Hansen and Hjerting in (1996). At the same time they demonstrated that Dahlia pinnata should more properly be designated D. x pinnata. D. x pinnata was shown to actually be a variant of D. sorensenii that had acquired hybrid qualities before it was introduced to Europe in the sixteenth century and formally named by Cavanilles. The original wild D. pinnata is presumed extinct. Further species continue to be described, Saar (2003) describing 35 species. However separation of the sections on morphological, cytologal and biocemical criteria has not been entirely satisfactory.
To date these sectional divisions have not been fully supported phylogenetically, which demonstrate only section Entemophyllon as a distinct sectional clade. The other major grouping is the Core Dahlia Clade (CDC), which includes most of section Dahlia. The remainder of the species occupy what has been described as the Variable Root Clade (VRC) which includes the small section Pseudodendron but also the monotypic section Epiphytum and a number of species from within section Dahlia. Outside of these three clades lie D. tubulata and D. merckii as a polytomy.
Horticulturally the sections retain some usage, section Pseudodendron being referred to as 'Tree Dahlias', Epiphytum as the 'Vine Dahlia'. The remaining two herbaceous sections being distinguished by their pinnules, opposing (Dahlia) or alternating (Entemophyllon).
SECTIONS
Sections (including chromosome numbers), with geographical distribution;
- Epiphytum Sherff (2n = 32)
10 m tall climber with aerial roots 5 cm thick and up to more than 20 m long; pinnules opposite
1 species, D. macdougallii Sherff
Mexico: Oaxaca
- Entemophyllon P. D. Sorensen (2n = 34)
6 species
Mexico: Hidalgo, Nuevo León, Tamaulipas, Querétaro, Durango, San Luis Potosí
- Pseudodendron P. D. Sorensen (2n = 32)
3 species + D. excelsa of uncertain identity
Mexico: Chiapas, Guerrero, Jalisco, Michoacan, Oaxaca, and
Costa Rica, El Salvador, Guatemala & Colombia
- Dahlia (2n = 32, 36 or 64)
24 species
Mexico: Distrito Federal, Guerrero, Hidalgo, Morelos, Nuevo León, Puebla, San Luis Potosí, Tamaulipas, Veracruz, Oaxaca, Puebla, Chiapas, México, Huehuetenango, Chihuahua, Durango, Michoacan & Guatemala
Only Pseudodendron (D. imperialis) and Dahlia (D. australis, D. coccinea) occur outside Mexico.
SPECIES
There are currently 42 accepted species in the Dahlia genus, but new species continue to be described.
ETYMOLOGY
The naming of the plant itself has long been a subject of some confusion. Many sources state that the name "Dahlia" was bestowed by the pioneering Swedish botanist and taxonomist Carl Linnaeus to honor his late student, Anders Dahl, author of Observationes Botanicae. However, Linnaeus died in 1778, more than eleven years before the plant was introduced into Europe in 1789, so while it is generally agreed that the plant was named in 1791 in honor of Dahl, who had died two years before, Linnaeus could not have been the one who did so. It was probably Abbe Antonio Jose Cavanilles, Director of the Royal Gardens of Madrid, who should be credited with the attempt to scientifically define the genus, since he not only received the first specimens from Mexico in 1789, but named the first three species that flowered from the cuttings.
Regardless of who bestowed it, the name was not so easily established. In 1805, German botanist Carl Ludwig Willdenow, asserting that the genus Dahlia Thunb. (published a year after Cavanilles's genus and now considered a synonym of Trichocladus) was more widely accepted, changed the plants' genus from Dahlia to Georgina; after the German-born naturalist Johann Gottlieb Georgi, a professor at the Imperial Academy of Sciences of St. Petersburg, Russia. He also reclassified and renamed the first three species grown, and identified, by Cavanilles. It was not until 1810, in a published article, that he officially adopted the Cavanilles' original designation of Dahlia. However, the name Georgina still persisted in Germany for the next few decades.
"Dahl" is a homophone of the Swedish word "dal", or "valley"; although it is not a true translation, the plant is sometimes referred to as the "valley flower".
DISTRIBUTION AND HABITAT
Predominantly Mexico, but some species are found ranging as far south as northern South America. D. australis occurs at least as far south as southwestern Guatemala, while D. coccinea and D. imperialis also occur in parts of Central America and northern South America. Dahlia is a genus of the uplands and mountains, being found at elevations between 1,500 and 3,700 meters, in what has been described as a "pine-oak woodland" vegetative zone. Most species have limited ranges scattered throughout many mountain ranges in Mexico.
ECOLOGY
The commonest pollinators are bees and small beetles.
PESTS AND DISEASES
Slugs and snails are serious pests in some parts of the world, particularly in spring when new growth is emerging through the soil. Earwigs can also disfigure the blooms. The other main pests likely to be encountered are aphids (usually on young stems and immature flower buds), red spider mite (causing foliage mottling and discolouration, worse in hot and dry conditions) and capsid bugs (resulting in contortion and holes at growing tips). Diseases affecting dahlias include powdery mildew, grey mould (Botrytis cinerea), verticillium wilt, dahlia smut (Entyloma calendulae f. dahliae), phytophthora and some plant viruses. Dahlias are a source of food for the larvae of some Lepidoptera species including Angle Shades, Common Swift, Ghost Moth and Large Yellow Underwing.
CULTIVATION
Dahlias grow naturally in climates which do not experience frost (the tubers are hardy to USDA Zone 8), consequently they are not adapted to withstand sub-zero temperatures. However, their tuberous nature enables them to survive periods of dormancy, and this characteristic means that gardeners in temperate climates with frosts can grow dahlias successfully, provided the tubers are lifted from the ground and stored in cool yet frost-free conditions during the winter. Planting the tubers quite deep (10 – 15 cm) also provides some protection. When in active growth, modern dahlia hybrids perform most successfully in well-watered yet free-draining soils, in situations receiving plenty of sunlight. Taller cultivars usually require some form of staking as they grow, and all garden dahlias need deadheading regularly, once flowering commences.
HORTICURAL CLASSIFICATION
HISTORY
The inappropriate term D. variabilis is often used to describe the cultivars of Dahlia since the correct parentage remains obscure, but probably involves Dahlia coccinea. In 1846 the Caledonia Horticultural Society of Edinburgh offered a prize of 2,000 pounds to the first person succeeding in producing a blue dahlia. This has to date not been accomplished. While dahlias produce anthocyanin, an element necessary for the production of the blue, to achieve a true blue color in a plant, the anthocyanin delphinidin needs six hydroxyl groups. To date dahlias have only developed five, so the closest that breeders have come to achieving a "blue" specimen are variations of mauve, purples and lilac hues.
By the beginning of the twentieth century a number of different types were recognised. These terms were based on shape or colour, and the National Dahlia Society included cactus, pompon, single, show and fancy in its 1904 guide. Many national societies developed their own classification systems until 1962 when the International Horticultural Congress agreed to develop an internationally recognised system at it Brussels meeting that year, and subsequently in Maryland in 1966. This culminated in the 1969 publication of The International Register of Dahlia Names by the Royal Horticultural Society which became the central registering authority.
This system depended primarily on the visibility of the central disc, whether it was open centred or whether only ray florets were apparent centrally (double bloom). The double bloom cultivars were then subdivided according to the way in which they were folded along their longitudinal axis, flat, involute (curled inwards) or revolute (curling backwards). If the end of the ray floret was split, they were considered fimbriated. Based on these characteristics, nine groups were defined plua a tenth miscellaneous group for any cultivars not fitting the above characteristics. Fimbriated dahlias were added in 2004, and two further groups (Single and Double orchid) in 2007. The last group to be added, Peony, first appeared in 2012.
In many cases the bloom diametre was then used to further label certain groups from miniature through to giant. This practice was abandoned in 2012.
MODERN SYSTEM (RHS)
There are now more than 57,000 registered cultivars, which are officially registered through the Royal Horticultural Society (RHS). The official register is The International Register of Dahlia Names 1969 (1995 reprint) which is updated by annual supplements. The original 1969 registry published about 14,000 cultivars adding a further 1700 by 1986 and in 2003 there were 18,000. Since then about a hundred new cultivars are added annually.
FLOWER TYPE
The official RHS classification lists fourteen groups, grouped by flower type, together with the abbreviations used by the RHS;
Group 1 – Single-flowered dahlias (Sin) — Flower has a central disc with a single outer ring of florets (which may overlap) encircling it, and which may be rounded or pointed.
Group 2 – Anemone-flowered dahlias (Anem) — The centre of the flower consists of dense elongated tubular florets, longer than the disc florets of Single dahlias, while the outer parts have one or more rings of flatter ray florets. Disc absent.
Group 3 – Collerette dahlias (Col) — Large flat florets forming a single outer ring around a central disc and which may overlap a smaller circle of florets closer to the centre, which have the appearance of a collar.
Group 4 – Waterlily dahlias (WL) — Double blooms, broad sparse curved, slightly curved or flat florets and very shallow in depth compared with other dahlias. Depth less than half the diameter of the bloom. Group 5 – Decorative dahlias (D) — Double blooms, ray florets broad, flat, involute no more than seventy five per cent of the longitudinal axis, slightly twisted and usually bluntly pointed. No visible central disc.
Group 6 – Ball dahlias (Ba)— Double blooms that are ball shaped or slightly flattened. Ray florets blunt or rounded at the tips, margins arranged spirally, involute for at least seventy five percent of the length of the florets. Larger than Pompons.
Group 7 – Pompon dahlias (Pom) — Double spherical miniature flowers made up entirely from florets that are curved inwards (involute) for their entire length (longitudinal axis), resembling a pompon.
Group 8 – Cactus dahlias (C) — Double blooms, ray florets pointed, with majority revolute (rolled) over more than fifty percent of their longitudinal axis, and straight or incurved. Narrower than Semi cactus.
Group 9 – Semi cactus dahlias (S–c)— Double blooms, very pointed ray florets, revolute for greater than twenty five percent and less than fifty percent of their longitudinal axis. Broad at the base and straight or incurved, almost spiky in appearance.
Group 10 – Miscellaneous dahlias (Misc) — not described in any other group.
Group 11 – Fimbriated dahlias (Fim) — ray florets evenly split or notched into two or more divisions, uniformly throughout the bloom, creating a fimbriated (fringed) effect. The petals may be flat, involute, revolute, straight, incurving or twisted.
Group 12 – Single Orchid (Star) dahlias (SinO) — single outer ring of florets surround a central disc. The ray florets are either involute or revolute.
Group 13 – Double Orchid dahlias (DblO) — Double blooms with triangular centres. The ray florets are narrowly lanceolate and are either involute or revolute. The central disc is absent.
Group 14 – Peony-flowered dahlias (P) — Large flowers with three or four rows of rays that are flattened and expanded and arranged irregularly. The rays surround a golden disc similar to that of Single dahlias.
FLOWER SIZE
Earlier versions of the registry subdivided some groups by flower size. Groups 4, 5, 8 and 9 were divided into five subgroups (A to E) from Giant to Miniature, and Group 6 into two subgroups, Small and Miniature. Dahlias were then described by Group and Subgroup, e.g. 5(d) ‘Ace Summer Sunset’. Some Dahlia Societies have continued this practice, but this is neither official nor standardised. As of 2013 The RHS uses two size descriptors
Dwarf Bedder (Dw.B.) — not usually exceeding 600 mm in height, e.g. 'Preston Park' (Sin/DwB)
Lilliput dahlias (Lil) — not usually exceeding 300 mm in height, with single, semi-double or double florets up to 26 mm in diameter. ("baby" or "top-mix" dahlias), e.g. 'Harvest Tiny Tot' (Misc/Lil)
Sizes can range from tiny micro dahlias with flowers less than 50mm to giants that are over 250mm in diameter. The groupings listed here are from the New Zealand Society.
Giant flowered cultivars have blooms with a diameter of over 250mm.
Large flowered cultivars have blooms with a diameter between 200mm-250mm.
Medium flowered cultivars have blooms with a diameter between 155mm-200mm.
Small flowered cultivars have blooms with a diameter between 115mm-155mm.
Miniature flowered cultivars have blooms with a diameter between 50mm-115mm.
Pompom flowered cultivars have blooms with a diameter less than 50mm.
In addition to the official classification and the terminology used by various dahlia societies, individual horticulturalists use a wide range of other descriptions, such as 'Incurved' and abbreviations in their catalogues, such as CO for Collarette.
BRANDING
Some plant growers include their brand name in the cultivar name. Thus Fides (part of the Dümmen Orange Group) in the Netherlands developed a series of cultivars which they named the Dahlinova Series, for example Dahlinova 'Carolina Burgundy'. These are Group 10 Miscellaneous in the RHS classification scheme.
DOUBLE DAHLIAS
In 1805, several new species were reported with red, purple, lilac, and pale yellow coloring, and the first true double flower was produced in Belgium. One of the more popular concepts of dahlia history, and the basis for many different interpretations and confusion, is that all the original discoveries were single flowered types, which, through hybridization and selective breeding, produced double forms. Many of the species of dahlias then, and now, have single flowered blooms. coccinea, the third dahlia to bloom in Europe, was a single. But two of the three drawings of dahlias by Dominguez, made in Mexico between 1570–77, showed definite characteristics of doubling. In the early days of the dahlia in Europe, the word "double" simply designated flowers with more than one row of petals. The greatest effort was now directed to developing improved types of double dahlias.
During the years 1805 to 1810 several people claimed to have produced a double dahlia. In 1805 Henry C. Andrews made a drawing of such a plant in the collection of Lady Holland, grown from seedlings sent that year from Madrid. Like other doubles of the time it did not resemble the doubles of today. The first modern double, or full double, appeared in Belgium; M. Donckelaar, Director of the Botanic Garden at Louvain, selected plants for that characteristic, and within a few years secured three fully double forms. By 1826 double varieties were being grown almost exclusively, and there was very little interest in the single forms. Up to this time all the so-called double dahlias had been purple, or tinged with purple, and it was doubted if a variety untinged with that color was obtainable.
In 1843, scented single forms of dahlias were first reported in Neu Verbass, Austria. D. crocea, a fragrant variety grown from one of the Humboldt seeds, was probably interbred with the single D. coccinea. A new scented species would not be introduced until the next century when the D. coronata was brought from Mexico to Germany in 1907.
The exact date the dahlia was introduced in the United States is uncertain. One of the first Dahlias in the USA may be the D. coccinea speciosissima grown by Mr William Leathe, of Cambridgeport, near Boston, around 1929. According to Edward Sayers "it attracted much admiration, and at that time was considered a very elegant flower, it was however soon eclipsed by that splendid scarlet, the Countess of Liverpool". However 9 cultivars were already listed in the catalog from Thornburn, 1825. And even earlier reference can be found in a catalogue from the Linnaean Botanical Garden, New York, 1820, that includes one scarlet, one purple, and two double orange Dahlias for sale.
Sayers stated that "No person has done more for the introduction and advancement of the culture of the Dahlia than George C. Thorburn, of New York, who yearly flowers many thousand plants at his place at Hallet's Cove, near Harlaem. The show there in the flowering season is a rich treat for the lovers of floriculture : for almost every variety can be seen growing in two large blocks or masses which lead from the road to the dwelling-house, and form a complete field of the Dahlia as a foreground to the house. Mr T. Hogg, Mr William Read, and many other well known florists, have also contributed much in the vicinity of New York, to the introduction of the Dahlia. Indeed so general has become the taste that almost every garden has its show of the Dahlia in the season." In Boston too there were many collections, a collection from the Messrs Hovey of Cambridgeport was also mentioned.
In 1835 Thomas Bridgeman, published a list of 160 double dahlias in his Florist's Guide. 60 of the choicest were supplied by Mr. G. C. Thornburn of Astoria, N.Y. who got most of them from contacts in the UK. Not a few of them had taken prices "at the English and American exhibitions".
"STARS OF DEVIL"
In 1872 J.T. van der Berg of Utrecht in the Netherlands, received a shipment of seeds and plants from a friend in Mexico. The entire shipment was badly rotted and appeared to be ruined, but van der Berg examined it carefully and found a small piece of root that seemed alive. He planted and carefully tended it; it grew into a plant that he identified as a dahlia. He made cuttings from the plant during the winter of 1872-1873. This was an entirely different type of flower, with a rich, red color and a high degree of doubling. In 1874 van der Berg catalogued it for sale, calling it Dahlia juarezii to honor Mexican President Benito Pablo Juarez, who had died the year before, and described it as "...equal to the beautiful color of the red poppy. Its form is very outstanding and different in every respect of all known dahlia flowers.".
This plant has perhaps had a greater influence on the popularity of the modern dahlia than any other. Called "Les Etoiles de Diable" (Stars of the Devil) in France and "Cactus dahlia" elsewhere, the edges of its petals rolled backwards, rather than forward, and this new form revolutionized the dahlia world. It was thought to be a distinct mutation since no other plant that resembled it could be found in the wild. Today it is assumed that D. juarezii had, at one time, existed in Mexico and subsequently disappeared. Nurserymen in Europe crossbred this plant with dahlias discovered earlier; the results became the progenitors of all modern dahlia hybrids today.
AWARD OF GARDEN MERIT (RHS)
As of 2015, 124 dahlia cultivars have gained the Royal Horticultural Society's Award of Garden Merit:
"Bednall beauty"
"Bishop of Llandaff"
"Clair de lune"
"David Howard"
"Ellen Huston"
"Fascination"
"Gallery art deco"
"Gallery Art Nouveau"
"Glorie van Heemstede"
"Honka"
"Moonfire"
"Twyning's After Eight"
USES
FLORICULTURE
The asterid eudicots contain two economically important geophyte genera, Dahlia and Liatris. Horticulturally the garden dahlia is usually treated as the cultigen D. variabilis Hort., which while being responsible for thousands of cultivars has an obscure taxonomic status.
OTHER
Today the dahlia is still considered one of the native ingredients in Oaxacan cuisine; several cultivars are still grown especially for their large, sweet potato-like tubers. Dacopa, an intense mocha-tasting extract from the roasted tubers, is used to flavor beverages throughout Central America.
In Europe and America, prior to the discovery of insulin in 1923, diabetics - as well as consumptives - were often given a substance called Atlantic starch or diabetic sugar, derived from inulin, a naturally occurring form of fruit sugar, extracted from dahlia tubers. Inulin is still used in clinical tests for kidney functionality.
WIKIPEDIA
RIUM, WP Kuala Lumpur, Malaysia.
Stemona curtisii Hook.f. Stemonaceae. CN; [Malay - Akar ratus, Akar seratus, Kemili hutan, Ubi kemili (sharing name with Plectranthus rotundifolius, a Lamiaceae), Pecah kelambu, Galak tua], Stemona. The vernacular names are often interchangeable used with Stemona tuberosa presumably non-native here and also many equally conflicting names and synonyms in various reports. Native to India (Nicobar Islands), Sri Lanka, Thailand and Malesia floristic zone. In peninsular Malaysia, occurrence is widespread, often in thickets near the sea, sometimes on limestone formations. Many scientific studies done to determine its phytochemical properties, but among the natives the root has been claimed an effective aphrodisiac.
Synonym(s):
Stemona minor Hook.f.
Ref. and suggested reading:
FRIM Flora Database
www.theplantlist.org/tpl/record/kew-288271
zipcodezoo.com/Plants/S/Stemona_curtisii/
proseanet.org/prosea/e-prosea_detail.php?frt=&id=1310
wannura.wordpress.com/2010/05/17/galak-tua-stemona-curtis...
RIUM, WP Kuala Lumpur, Malaysia.
Stemona curtisii Hook.f. Stemonaceae. CN; [Malay - Akar ratus, Akar seratus, Kemili hutan, Ubi kemili (sharing name with Plectranthus rotundifolius, a Lamiaceae), Pecah kelambu, Galak tua], Stemona. The vernacular names are often interchangeable used with Stemona tuberosa presumably non-native here and also many equally conflicting names and synonyms in various reports. Native to India (Nicobar Islands), Sri Lanka, Thailand and Malesia floristic zone. In peninsular Malaysia, occurrence is widespread, often in thickets near the sea, sometimes on limestone formations. Many scientific studies done to determine its phytochemical properties, but among the natives the root has been claimed an effective aphrodisiac.
Synonym(s):
Stemona minor Hook.f.
Ref. and suggested reading:
FRIM Flora Database
www.theplantlist.org/tpl/record/kew-288271
zipcodezoo.com/Plants/S/Stemona_curtisii/
proseanet.org/prosea/e-prosea_detail.php?frt=&id=1310
wannura.wordpress.com/2010/05/17/galak-tua-stemona-curtis...
Basella alba is a fast-growing, soft-stemmed vine, reaching 10 metres (33 ft) in length. It is found in tropical Asia and Africa where it is widely used as a leaf vegetable. Its thick, semi-succulent, heart-shaped leaves have a mild flavour and mucilaginous texture. It is rich in vitamins A and C, iron and calcium. It has been shown to contain certain phenolic phytochemicals and it has antioxidant properties.
Source: Wikipedia
It is just amazing how we are surrounded by numerous plants that provide us with virtually all the essential nutrients needed for healthy living. Apart from these beneficial nutrients, plants also provide us with natural phytochemicals that are equally essential for the healthy functioning o...
RIUM, WP Kuala Lumpur, Malaysia.
Stemona curtisii Hook.f. Stemonaceae. CN; [Malay - Akar ratus, Akar seratus, Kemili hutan, Ubi kemili (sharing name with Plectranthus rotundifolius, a Lamiaceae), Pecah kelambu, Galak tua], Stemona. The vernacular names are often interchangeable used with Stemona tuberosa presumably non-native here and also many equally conflicting names and synonyms in various reports. Native to India (Nicobar Islands), Sri Lanka, Thailand and Malesia floristic zone. In peninsular Malaysia, occurrence is widespread, often in thickets near the sea, sometimes on limestone formations. Many scientific studies done to determine its phytochemical properties, but among the natives the root has been claimed an effective aphrodisiac.
Synonym(s):
Stemona minor Hook.f.
Ref. and suggested reading:
FRIM Flora Database
www.theplantlist.org/tpl/record/kew-288271
zipcodezoo.com/Plants/S/Stemona_curtisii/
proseanet.org/prosea/e-prosea_detail.php?frt=&id=1310
wannura.wordpress.com/2010/05/17/galak-tua-stemona-curtis...
. . . this picture is taken in my garden
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Dahlia (UK /deɪliə/ or US /dɑːliə/) is a genus of bushy, tuberous, herbaceous perennial plants native to Mexico. A member of the Asteraceae (or Compositae), dicotyledonous plants, related species include the sunflower, daisy, chrysanthemum, and zinnia. There are 42 species of dahlia, with hybrids commonly grown as garden plants. Flower forms are variable, with one head per stem; these can be as small as 5.1 cm diameter or up to 30 cm ("dinner plate"). This great variety results from dahlias being octoploids—that is, they have eight sets of homologous chromosomes, whereas most plants have only two. In addition, dahlias also contain many transposons - genetic pieces that move from place to place upon an allele - which contributes to their manifesting such great diversity.
The stems are leafy, ranging in height from as low as 30 cm to more than 1.8–2.4 m. The majority of species do not produce scented flowers or cultivars. Like most plants that do not attract pollinating insects through scent, they are brightly colored, displaying most hues, with the exception of blue.
The dahlia was declared the national flower of Mexico in 1963. The tubers were grown as a food crop by the Aztecs, but this use largely died out after the Spanish Conquest. Attempts to introduce the tubers as a food crop in Europe were unsuccessful.
DESCRIPTION
Perennial plants, with mostly tuberous roots. While some have herbaceous stems, others have stems which lignify in the absence of secondary tissue and resprout following winter dormancy, allowing further seasons of growth. as a member of the Asteraceae the flower head is actually a composite (hence the older name Compositae) with both central disc florets and surrounding ray florets. Each floret is a flower in its own right, but is often incorrectly described as a petal, particularly by horticulturalists. The modern mame Asteraceae refers to the appearance of a star with surrounding rays.
TAXONOMY
HISTORY
EARLY HISTORY
Spaniards reported finding the plants growing in Mexico in 1525, but the earliest known description is by Francisco Hernández, physician to Philip II, who was ordered to visit Mexico in 1570 to study the "natural products of that country". They were used as a source of food by the indigenous peoples, and were both gathered in the wild and cultivated. The Aztecs used them to treat epilepsy, and employed the long hollow stem of the (Dahlia imperalis) for water pipes. The indigenous peoples variously identified the plants as "Chichipatl" (Toltecs) and "Acocotle" or "Cocoxochitl" (Aztecs). From Hernandez' perception of Aztec, to Spanish, through various other translations, the word is "water cane", "water pipe", "water pipe flower", "hollow stem flower" and "cane flower". All these refer to the hollowness of the plants' stem.Hernandez described two varieties of dahlias (the pinwheel-like Dahlia pinnata and the huge Dahlia imperialis) as well as other medicinal plants of New Spain. Francisco Dominguez, a Hidalgo gentleman who accompanied Hernandez on part of his seven-year study, made a series of drawings to supplement the four volume report. Three of his drawings showed plants with flowers: two resembled the modern bedding dahlia, and one resembled the species Dahlia merki; all displayed a high degree of doubleness. In 1578 the manuscript, entitled Nova Plantarum, Animalium et Mineralium Mexicanorum Historia, was sent back to the Escorial in Madrid; they were not translated into Latin by Francisco Ximenes until 1615. In 1640, Francisco Cesi, President of the Academia Linei of Rome, bought the Ximenes translation, and after annotating it, published it in 1649-1651 in two volumes as Rerum Medicarum Novae Hispaniae Thesaurus Seu Nova Plantarium, Animalium et Mineraliuím Mexicanorum Historia. The original manuscripts were destroyed in a fire in the mid-1600s.
EUROPEAN INTRODUCTION
In 1787, the French botanist Nicolas-Joseph Thiéry de Menonville, sent to Mexico to steal the cochineal insect valued for its scarlet dye, reported the strangely beautiful flowers he had seen growing in a garden in Oaxaca. In 1789, Vicente Cervantes, Director of the Botanical Garden at Mexico City, sent "plant parts" to Abbe Antonio José Cavanilles, Director of the Royal Gardens of Madrid. Cavanilles flowered one plant that same year, then the second one a year later. In 1791 he called the new growths "Dahlia" for Anders Dahl. The first plant was called Dahlia pinnata after its pinnate foliage; the second, Dahlia rosea for its rose-purple color. In 1796 Cavanilles flowered a third plant from the parts sent by Cervantes, which he named Dahlia coccinea for its scarlet color.In 1798, Cavanilles sent D. Pinnata seeds to Parma, Italy. That year, the Marchioness of Bute, wife of The Earl of Bute, the English Ambassador to Spain, obtained a few seeds from Cavanilles and sent them to Kew Gardens, where they flowered but were lost after two to three years. In the following years Madrid sent seeds to Berlin and Dresden in Germany, and to Turin and Thiene in Italy. In 1802, Cavanilles sent tubers of "these three" (D. pinnata, D. rosea, D. coccinea) to Swiss botanist Augustin Pyramus de Candolle at University of Montpelier in France, Andre Thouin at the Jardin des Plantes in Paris and Scottish botanist William Aiton at Kew Gardens. That same year, John Fraser, English nurseryman and later botanical collector to the Czar of Russia, brought D. coccinea seeds from Paris to the Apothecaries Gardens in England, where they flowered in his greenhouse a year later, providing Botanical Magazine with an illustration.In 1804, a new species, Dahlia sambucifolia, was successfully grown at Holland House, Kensington. Whilst in Madrid in 1804, Lady Holland was given either dahlia seeds or tubers by Cavanilles. She sent them back to England, to Lord Holland's librarian Mr Buonaiuti at Holland House, who successfully raised the plants. A year later, Buonaiuti produced two double flowers. The plants raised in 1804 did not survive; new stock was brought from France in 1815. In 1824, Lord Holland sent his wife a note containing the following verse:
"The dahlia you brought to our isle
Your praises for ever shall speak;
Mid gardens as sweet as your smile,
And in colour as bright as your cheek."
In 1805, German naturalist Alexander von Humboldt sent more seeds from Mexico to Aiton in England, Thouin in Paris, and Christoph Friedrich Otto, director of the Berlin Botanical Garden. More significantly, he sent seeds to botanist Carl Ludwig Willdenow in Germany. Willdenow now reclassified the rapidly growing number of species, changing the genus from Dahlia to Georgina; after naturalist Johann Gottlieb Georgi. He combined the Cavanilles species D. pinnata and D. rosea under the name of Georgina variabilis; D. coccinea was still held to be a separate species, which he renamed Georgina coccinea.
CLASSIFICATION
Since 1789 when Cavanilles first flowered the dahlia in Europe, there has been an ongoing effort by many growers, botanists and taxonomists, to determine the development of the dahlia to modern times. At least 85 species have been reported: approximately 25 of these were first reported from the wild, the remainder appeared in gardens in Europe. They were considered hybrids, the results of crossing between previously reported species, or developed from the seeds sent by Humboldt from Mexico in 1805, or perhaps from some other undocumented seeds that had found their way to Europe. Several of these were soon discovered to be identical with earlier reported species, but the greatest number are new varieties. Morphological variation is highly pronounced in the dahlia. William John Cooper Lawrence, who hybridized hundreds of families of dahlias in the 1920s, stated: "I have not yet seen any two plants in the families I have raised which were not to be distinguished one from the other. Constant reclassification of the 85 reported species has resulted in a considerably smaller number of distinct species, as there is a great deal of disagreement today between systematists over classification.
In 1829, all species growing in Europe were reclassified under an all-encompassing name of D. variabilis, Desf., though this is not an accepted name. Through the interspecies cross of the Humboldt seeds and the Cavanilles species, 22 new species were reported by that year, all of which had been classified in different ways by several different taxonomists, creating considerable confusion as to which species was which.
In 1830 William Smith suggested that all dahlia species could be divided into two groups for color, red-tinged and purple-tinged. In investigating this idea Lawrence determined that with the exception of D. variabilis, all dahlia species may be assigned to one of two groups for flower-colour: Group I (ivory-magenta) or Group II (yellow-orange-scarlet).
CIRCUMSCRIPTION
The genus Dahlia is situated in the Asteroideae subfamily of the Asteraceae, in the Coreopsideae tribe. Within that tribe it is the second largest genus, after Coreopsis, and appears as a well defined clade within the Coreopsideae.
SUBDIVISION
INFRAGENERIC SUBDIVISION
Sherff (1955), in the first modern taxonomy described three sections for the 18 species he recognised, Pseudodendron, Epiphytum and Dahlia. By 1969 Sørensen recognised 29 species and four sections by splitting off Entemophyllon from section Dahlia. By contrast Giannasi (1975) using a phytochemical analysis based on flavonoids, reduced the genus to just two sections, Entemophyllon and Dahlia, the latter having three subsections, Pseudodendron, Dahlia, and Merckii. Sørensen then issued a further revision in 1980, incorporating subsection Merckii in his original section Dahlia. When he described two new species in the 1980s (Dahlia tubulata and D. congestifolia), he placed them within his existing sections. A further species, Dahlia sorensenii was added by Hansen and Hjerting in (1996). At the same time they demonstrated that Dahlia pinnata should more properly be designated D. x pinnata. D. x pinnata was shown to actually be a variant of D. sorensenii that had acquired hybrid qualities before it was introduced to Europe in the sixteenth century and formally named by Cavanilles. The original wild D. pinnata is presumed extinct. Further species continue to be described, Saar (2003) describing 35 species. However separation of the sections on morphological, cytologal and biocemical criteria has not been entirely satisfactory.
To date these sectional divisions have not been fully supported phylogenetically, which demonstrate only section Entemophyllon as a distinct sectional clade. The other major grouping is the Core Dahlia Clade (CDC), which includes most of section Dahlia. The remainder of the species occupy what has been described as the Variable Root Clade (VRC) which includes the small section Pseudodendron but also the monotypic section Epiphytum and a number of species from within section Dahlia. Outside of these three clades lie D. tubulata and D. merckii as a polytomy.
Horticulturally the sections retain some usage, section Pseudodendron being referred to as 'Tree Dahlias', Epiphytum as the 'Vine Dahlia'. The remaining two herbaceous sections being distinguished by their pinnules, opposing (Dahlia) or alternating (Entemophyllon).
SECTIONS
Sections (including chromosome numbers), with geographical distribution;
- Epiphytum Sherff (2n = 32)
10 m tall climber with aerial roots 5 cm thick and up to more than 20 m long; pinnules opposite
1 species, D. macdougallii Sherff
Mexico: Oaxaca
- Entemophyllon P. D. Sorensen (2n = 34)
6 species
Mexico: Hidalgo, Nuevo León, Tamaulipas, Querétaro, Durango, San Luis Potosí
- Pseudodendron P. D. Sorensen (2n = 32)
3 species + D. excelsa of uncertain identity
Mexico: Chiapas, Guerrero, Jalisco, Michoacan, Oaxaca, and
Costa Rica, El Salvador, Guatemala & Colombia
- Dahlia (2n = 32, 36 or 64)
24 species
Mexico: Distrito Federal, Guerrero, Hidalgo, Morelos, Nuevo León, Puebla, San Luis Potosí, Tamaulipas, Veracruz, Oaxaca, Puebla, Chiapas, México, Huehuetenango, Chihuahua, Durango, Michoacan & Guatemala
Only Pseudodendron (D. imperialis) and Dahlia (D. australis, D. coccinea) occur outside Mexico.
SPECIES
There are currently 42 accepted species in the Dahlia genus, but new species continue to be described.
ETYMOLOGY
The naming of the plant itself has long been a subject of some confusion. Many sources state that the name "Dahlia" was bestowed by the pioneering Swedish botanist and taxonomist Carl Linnaeus to honor his late student, Anders Dahl, author of Observationes Botanicae. However, Linnaeus died in 1778, more than eleven years before the plant was introduced into Europe in 1789, so while it is generally agreed that the plant was named in 1791 in honor of Dahl, who had died two years before, Linnaeus could not have been the one who did so. It was probably Abbe Antonio Jose Cavanilles, Director of the Royal Gardens of Madrid, who should be credited with the attempt to scientifically define the genus, since he not only received the first specimens from Mexico in 1789, but named the first three species that flowered from the cuttings.
Regardless of who bestowed it, the name was not so easily established. In 1805, German botanist Carl Ludwig Willdenow, asserting that the genus Dahlia Thunb. (published a year after Cavanilles's genus and now considered a synonym of Trichocladus) was more widely accepted, changed the plants' genus from Dahlia to Georgina; after the German-born naturalist Johann Gottlieb Georgi, a professor at the Imperial Academy of Sciences of St. Petersburg, Russia. He also reclassified and renamed the first three species grown, and identified, by Cavanilles. It was not until 1810, in a published article, that he officially adopted the Cavanilles' original designation of Dahlia. However, the name Georgina still persisted in Germany for the next few decades.
"Dahl" is a homophone of the Swedish word "dal", or "valley"; although it is not a true translation, the plant is sometimes referred to as the "valley flower".
DISTRIBUTION AND HABITAT
Predominantly Mexico, but some species are found ranging as far south as northern South America. D. australis occurs at least as far south as southwestern Guatemala, while D. coccinea and D. imperialis also occur in parts of Central America and northern South America. Dahlia is a genus of the uplands and mountains, being found at elevations between 1,500 and 3,700 meters, in what has been described as a "pine-oak woodland" vegetative zone. Most species have limited ranges scattered throughout many mountain ranges in Mexico.
ECOLOGY
The commonest pollinators are bees and small beetles.
PESTS AND DISEASES
Slugs and snails are serious pests in some parts of the world, particularly in spring when new growth is emerging through the soil. Earwigs can also disfigure the blooms. The other main pests likely to be encountered are aphids (usually on young stems and immature flower buds), red spider mite (causing foliage mottling and discolouration, worse in hot and dry conditions) and capsid bugs (resulting in contortion and holes at growing tips). Diseases affecting dahlias include powdery mildew, grey mould (Botrytis cinerea), verticillium wilt, dahlia smut (Entyloma calendulae f. dahliae), phytophthora and some plant viruses. Dahlias are a source of food for the larvae of some Lepidoptera species including Angle Shades, Common Swift, Ghost Moth and Large Yellow Underwing.
CULTIVATION
Dahlias grow naturally in climates which do not experience frost (the tubers are hardy to USDA Zone 8), consequently they are not adapted to withstand sub-zero temperatures. However, their tuberous nature enables them to survive periods of dormancy, and this characteristic means that gardeners in temperate climates with frosts can grow dahlias successfully, provided the tubers are lifted from the ground and stored in cool yet frost-free conditions during the winter. Planting the tubers quite deep (10 – 15 cm) also provides some protection. When in active growth, modern dahlia hybrids perform most successfully in well-watered yet free-draining soils, in situations receiving plenty of sunlight. Taller cultivars usually require some form of staking as they grow, and all garden dahlias need deadheading regularly, once flowering commences.
HORTICURAL CLASSIFICATION
HISTORY
The inappropriate term D. variabilis is often used to describe the cultivars of Dahlia since the correct parentage remains obscure, but probably involves Dahlia coccinea. In 1846 the Caledonia Horticultural Society of Edinburgh offered a prize of 2,000 pounds to the first person succeeding in producing a blue dahlia. This has to date not been accomplished. While dahlias produce anthocyanin, an element necessary for the production of the blue, to achieve a true blue color in a plant, the anthocyanin delphinidin needs six hydroxyl groups. To date dahlias have only developed five, so the closest that breeders have come to achieving a "blue" specimen are variations of mauve, purples and lilac hues.
By the beginning of the twentieth century a number of different types were recognised. These terms were based on shape or colour, and the National Dahlia Society included cactus, pompon, single, show and fancy in its 1904 guide. Many national societies developed their own classification systems until 1962 when the International Horticultural Congress agreed to develop an internationally recognised system at it Brussels meeting that year, and subsequently in Maryland in 1966. This culminated in the 1969 publication of The International Register of Dahlia Names by the Royal Horticultural Society which became the central registering authority.
This system depended primarily on the visibility of the central disc, whether it was open centred or whether only ray florets were apparent centrally (double bloom). The double bloom cultivars were then subdivided according to the way in which they were folded along their longitudinal axis, flat, involute (curled inwards) or revolute (curling backwards). If the end of the ray floret was split, they were considered fimbriated. Based on these characteristics, nine groups were defined plua a tenth miscellaneous group for any cultivars not fitting the above characteristics. Fimbriated dahlias were added in 2004, and two further groups (Single and Double orchid) in 2007. The last group to be added, Peony, first appeared in 2012.
In many cases the bloom diametre was then used to further label certain groups from miniature through to giant. This practice was abandoned in 2012.
MODERN SYSTEM (RHS)
There are now more than 57,000 registered cultivars, which are officially registered through the Royal Horticultural Society (RHS). The official register is The International Register of Dahlia Names 1969 (1995 reprint) which is updated by annual supplements. The original 1969 registry published about 14,000 cultivars adding a further 1700 by 1986 and in 2003 there were 18,000. Since then about a hundred new cultivars are added annually.
FLOWER TYPE
The official RHS classification lists fourteen groups, grouped by flower type, together with the abbreviations used by the RHS;
Group 1 – Single-flowered dahlias (Sin) — Flower has a central disc with a single outer ring of florets (which may overlap) encircling it, and which may be rounded or pointed.
Group 2 – Anemone-flowered dahlias (Anem) — The centre of the flower consists of dense elongated tubular florets, longer than the disc florets of Single dahlias, while the outer parts have one or more rings of flatter ray florets. Disc absent.
Group 3 – Collerette dahlias (Col) — Large flat florets forming a single outer ring around a central disc and which may overlap a smaller circle of florets closer to the centre, which have the appearance of a collar.
Group 4 – Waterlily dahlias (WL) — Double blooms, broad sparse curved, slightly curved or flat florets and very shallow in depth compared with other dahlias. Depth less than half the diameter of the bloom. Group 5 – Decorative dahlias (D) — Double blooms, ray florets broad, flat, involute no more than seventy five per cent of the longitudinal axis, slightly twisted and usually bluntly pointed. No visible central disc.
Group 6 – Ball dahlias (Ba)— Double blooms that are ball shaped or slightly flattened. Ray florets blunt or rounded at the tips, margins arranged spirally, involute for at least seventy five percent of the length of the florets. Larger than Pompons.
Group 7 – Pompon dahlias (Pom) — Double spherical miniature flowers made up entirely from florets that are curved inwards (involute) for their entire length (longitudinal axis), resembling a pompon.
Group 8 – Cactus dahlias (C) — Double blooms, ray florets pointed, with majority revolute (rolled) over more than fifty percent of their longitudinal axis, and straight or incurved. Narrower than Semi cactus.
Group 9 – Semi cactus dahlias (S–c)— Double blooms, very pointed ray florets, revolute for greater than twenty five percent and less than fifty percent of their longitudinal axis. Broad at the base and straight or incurved, almost spiky in appearance.
Group 10 – Miscellaneous dahlias (Misc) — not described in any other group.
Group 11 – Fimbriated dahlias (Fim) — ray florets evenly split or notched into two or more divisions, uniformly throughout the bloom, creating a fimbriated (fringed) effect. The petals may be flat, involute, revolute, straight, incurving or twisted.
Group 12 – Single Orchid (Star) dahlias (SinO) — single outer ring of florets surround a central disc. The ray florets are either involute or revolute.
Group 13 – Double Orchid dahlias (DblO) — Double blooms with triangular centres. The ray florets are narrowly lanceolate and are either involute or revolute. The central disc is absent.
Group 14 – Peony-flowered dahlias (P) — Large flowers with three or four rows of rays that are flattened and expanded and arranged irregularly. The rays surround a golden disc similar to that of Single dahlias.
FLOWER SIZE
Earlier versions of the registry subdivided some groups by flower size. Groups 4, 5, 8 and 9 were divided into five subgroups (A to E) from Giant to Miniature, and Group 6 into two subgroups, Small and Miniature. Dahlias were then described by Group and Subgroup, e.g. 5(d) ‘Ace Summer Sunset’. Some Dahlia Societies have continued this practice, but this is neither official nor standardised. As of 2013 The RHS uses two size descriptors
Dwarf Bedder (Dw.B.) — not usually exceeding 600 mm in height, e.g. 'Preston Park' (Sin/DwB)
Lilliput dahlias (Lil) — not usually exceeding 300 mm in height, with single, semi-double or double florets up to 26 mm in diameter. ("baby" or "top-mix" dahlias), e.g. 'Harvest Tiny Tot' (Misc/Lil)
Sizes can range from tiny micro dahlias with flowers less than 50mm to giants that are over 250mm in diameter. The groupings listed here are from the New Zealand Society.
Giant flowered cultivars have blooms with a diameter of over 250mm.
Large flowered cultivars have blooms with a diameter between 200mm-250mm.
Medium flowered cultivars have blooms with a diameter between 155mm-200mm.
Small flowered cultivars have blooms with a diameter between 115mm-155mm.
Miniature flowered cultivars have blooms with a diameter between 50mm-115mm.
Pompom flowered cultivars have blooms with a diameter less than 50mm.
In addition to the official classification and the terminology used by various dahlia societies, individual horticulturalists use a wide range of other descriptions, such as 'Incurved' and abbreviations in their catalogues, such as CO for Collarette.
BRANDING
Some plant growers include their brand name in the cultivar name. Thus Fides (part of the Dümmen Orange Group) in the Netherlands developed a series of cultivars which they named the Dahlinova Series, for example Dahlinova 'Carolina Burgundy'. These are Group 10 Miscellaneous in the RHS classification scheme.
DOUBLE DAHLIAS
In 1805, several new species were reported with red, purple, lilac, and pale yellow coloring, and the first true double flower was produced in Belgium. One of the more popular concepts of dahlia history, and the basis for many different interpretations and confusion, is that all the original discoveries were single flowered types, which, through hybridization and selective breeding, produced double forms. Many of the species of dahlias then, and now, have single flowered blooms. coccinea, the third dahlia to bloom in Europe, was a single. But two of the three drawings of dahlias by Dominguez, made in Mexico between 1570–77, showed definite characteristics of doubling. In the early days of the dahlia in Europe, the word "double" simply designated flowers with more than one row of petals. The greatest effort was now directed to developing improved types of double dahlias.
During the years 1805 to 1810 several people claimed to have produced a double dahlia. In 1805 Henry C. Andrews made a drawing of such a plant in the collection of Lady Holland, grown from seedlings sent that year from Madrid. Like other doubles of the time it did not resemble the doubles of today. The first modern double, or full double, appeared in Belgium; M. Donckelaar, Director of the Botanic Garden at Louvain, selected plants for that characteristic, and within a few years secured three fully double forms. By 1826 double varieties were being grown almost exclusively, and there was very little interest in the single forms. Up to this time all the so-called double dahlias had been purple, or tinged with purple, and it was doubted if a variety untinged with that color was obtainable.
In 1843, scented single forms of dahlias were first reported in Neu Verbass, Austria. D. crocea, a fragrant variety grown from one of the Humboldt seeds, was probably interbred with the single D. coccinea. A new scented species would not be introduced until the next century when the D. coronata was brought from Mexico to Germany in 1907.
The exact date the dahlia was introduced in the United States is uncertain. One of the first Dahlias in the USA may be the D. coccinea speciosissima grown by Mr William Leathe, of Cambridgeport, near Boston, around 1929. According to Edward Sayers "it attracted much admiration, and at that time was considered a very elegant flower, it was however soon eclipsed by that splendid scarlet, the Countess of Liverpool". However 9 cultivars were already listed in the catalog from Thornburn, 1825. And even earlier reference can be found in a catalogue from the Linnaean Botanical Garden, New York, 1820, that includes one scarlet, one purple, and two double orange Dahlias for sale.
Sayers stated that "No person has done more for the introduction and advancement of the culture of the Dahlia than George C. Thorburn, of New York, who yearly flowers many thousand plants at his place at Hallet's Cove, near Harlaem. The show there in the flowering season is a rich treat for the lovers of floriculture : for almost every variety can be seen growing in two large blocks or masses which lead from the road to the dwelling-house, and form a complete field of the Dahlia as a foreground to the house. Mr T. Hogg, Mr William Read, and many other well known florists, have also contributed much in the vicinity of New York, to the introduction of the Dahlia. Indeed so general has become the taste that almost every garden has its show of the Dahlia in the season." In Boston too there were many collections, a collection from the Messrs Hovey of Cambridgeport was also mentioned.
In 1835 Thomas Bridgeman, published a list of 160 double dahlias in his Florist's Guide. 60 of the choicest were supplied by Mr. G. C. Thornburn of Astoria, N.Y. who got most of them from contacts in the UK. Not a few of them had taken prices "at the English and American exhibitions".
"STARS OF DEVIL"
In 1872 J.T. van der Berg of Utrecht in the Netherlands, received a shipment of seeds and plants from a friend in Mexico. The entire shipment was badly rotted and appeared to be ruined, but van der Berg examined it carefully and found a small piece of root that seemed alive. He planted and carefully tended it; it grew into a plant that he identified as a dahlia. He made cuttings from the plant during the winter of 1872-1873. This was an entirely different type of flower, with a rich, red color and a high degree of doubling. In 1874 van der Berg catalogued it for sale, calling it Dahlia juarezii to honor Mexican President Benito Pablo Juarez, who had died the year before, and described it as "...equal to the beautiful color of the red poppy. Its form is very outstanding and different in every respect of all known dahlia flowers.".
This plant has perhaps had a greater influence on the popularity of the modern dahlia than any other. Called "Les Etoiles de Diable" (Stars of the Devil) in France and "Cactus dahlia" elsewhere, the edges of its petals rolled backwards, rather than forward, and this new form revolutionized the dahlia world. It was thought to be a distinct mutation since no other plant that resembled it could be found in the wild. Today it is assumed that D. juarezii had, at one time, existed in Mexico and subsequently disappeared. Nurserymen in Europe crossbred this plant with dahlias discovered earlier; the results became the progenitors of all modern dahlia hybrids today.
AWARD OF GARDEN MERIT (RHS)
As of 2015, 124 dahlia cultivars have gained the Royal Horticultural Society's Award of Garden Merit:
"Bednall beauty"
"Bishop of Llandaff"
"Clair de lune"
"David Howard"
"Ellen Huston"
"Fascination"
"Gallery art deco"
"Gallery Art Nouveau"
"Glorie van Heemstede"
"Honka"
"Moonfire"
"Twyning's After Eight"
USES
FLORICULTURE
The asterid eudicots contain two economically important geophyte genera, Dahlia and Liatris. Horticulturally the garden dahlia is usually treated as the cultigen D. variabilis Hort., which while being responsible for thousands of cultivars has an obscure taxonomic status.
OTHER
Today the dahlia is still considered one of the native ingredients in Oaxacan cuisine; several cultivars are still grown especially for their large, sweet potato-like tubers. Dacopa, an intense mocha-tasting extract from the roasted tubers, is used to flavor beverages throughout Central America.
In Europe and America, prior to the discovery of insulin in 1923, diabetics - as well as consumptives - were often given a substance called Atlantic starch or diabetic sugar, derived from inulin, a naturally occurring form of fruit sugar, extracted from dahlia tubers. Inulin is still used in clinical tests for kidney functionality.
WIKIPEDIA
The "passion" here is related to the Passion of Jesus Christ.
www.phytochemicals.info/plants/passion-fruit.php
Ezequiel´s Liqueur Manufacturing
Ribeira Grande
São Miguel
Açores
Portugal 2000
Dahlia (UK /deɪliə/ or US /dɑːliə/) is a genus of bushy, tuberous, herbaceous perennial plants native to Mexico. A member of the Asteraceae (or Compositae), dicotyledonous plants, related species include the sunflower, daisy, chrysanthemum, and zinnia. There are 42 species of dahlia, with hybrids commonly grown as garden plants. Flower forms are variable, with one head per stem; these can be as small as 5.1 cm diameter or up to 30 cm ("dinner plate"). This great variety results from dahlias being octoploids—that is, they have eight sets of homologous chromosomes, whereas most plants have only two. In addition, dahlias also contain many transposons - genetic pieces that move from place to place upon an allele - which contributes to their manifesting such great diversity.
The stems are leafy, ranging in height from as low as 30 cm to more than 1.8–2.4 m. The majority of species do not produce scented flowers or cultivars. Like most plants that do not attract pollinating insects through scent, they are brightly colored, displaying most hues, with the exception of blue.
The dahlia was declared the national flower of Mexico in 1963. The tubers were grown as a food crop by the Aztecs, but this use largely died out after the Spanish Conquest. Attempts to introduce the tubers as a food crop in Europe were unsuccessful.
DESCRIPTION
Perennial plants, with mostly tuberous roots. While some have herbaceous stems, others have stems which lignify in the absence of secondary tissue and resprout following winter dormancy, allowing further seasons of growth. as a member of the Asteraceae the flower head is actually a composite (hence the older name Compositae) with both central disc florets and surrounding ray florets. Each floret is a flower in its own right, but is often incorrectly described as a petal, particularly by horticulturalists. The modern mame Asteraceae refers to the appearance of a star with surrounding rays.
TAXONOMY
HISTORY
EARLY HISTORY
Spaniards reported finding the plants growing in Mexico in 1525, but the earliest known description is by Francisco Hernández, physician to Philip II, who was ordered to visit Mexico in 1570 to study the "natural products of that country". They were used as a source of food by the indigenous peoples, and were both gathered in the wild and cultivated. The Aztecs used them to treat epilepsy, and employed the long hollow stem of the (Dahlia imperalis) for water pipes. The indigenous peoples variously identified the plants as "Chichipatl" (Toltecs) and "Acocotle" or "Cocoxochitl" (Aztecs). From Hernandez' perception of Aztec, to Spanish, through various other translations, the word is "water cane", "water pipe", "water pipe flower", "hollow stem flower" and "cane flower". All these refer to the hollowness of the plants' stem.Hernandez described two varieties of dahlias (the pinwheel-like Dahlia pinnata and the huge Dahlia imperialis) as well as other medicinal plants of New Spain. Francisco Dominguez, a Hidalgo gentleman who accompanied Hernandez on part of his seven-year study, made a series of drawings to supplement the four volume report. Three of his drawings showed plants with flowers: two resembled the modern bedding dahlia, and one resembled the species Dahlia merki; all displayed a high degree of doubleness. In 1578 the manuscript, entitled Nova Plantarum, Animalium et Mineralium Mexicanorum Historia, was sent back to the Escorial in Madrid; they were not translated into Latin by Francisco Ximenes until 1615. In 1640, Francisco Cesi, President of the Academia Linei of Rome, bought the Ximenes translation, and after annotating it, published it in 1649-1651 in two volumes as Rerum Medicarum Novae Hispaniae Thesaurus Seu Nova Plantarium, Animalium et Mineraliuím Mexicanorum Historia. The original manuscripts were destroyed in a fire in the mid-1600s.
EUROPEAN INTRODUCTION
In 1787, the French botanist Nicolas-Joseph Thiéry de Menonville, sent to Mexico to steal the cochineal insect valued for its scarlet dye, reported the strangely beautiful flowers he had seen growing in a garden in Oaxaca. In 1789, Vicente Cervantes, Director of the Botanical Garden at Mexico City, sent "plant parts" to Abbe Antonio José Cavanilles, Director of the Royal Gardens of Madrid. Cavanilles flowered one plant that same year, then the second one a year later. In 1791 he called the new growths "Dahlia" for Anders Dahl. The first plant was called Dahlia pinnata after its pinnate foliage; the second, Dahlia rosea for its rose-purple color. In 1796 Cavanilles flowered a third plant from the parts sent by Cervantes, which he named Dahlia coccinea for its scarlet color.In 1798, Cavanilles sent D. Pinnata seeds to Parma, Italy. That year, the Marchioness of Bute, wife of The Earl of Bute, the English Ambassador to Spain, obtained a few seeds from Cavanilles and sent them to Kew Gardens, where they flowered but were lost after two to three years. In the following years Madrid sent seeds to Berlin and Dresden in Germany, and to Turin and Thiene in Italy. In 1802, Cavanilles sent tubers of "these three" (D. pinnata, D. rosea, D. coccinea) to Swiss botanist Augustin Pyramus de Candolle at University of Montpelier in France, Andre Thouin at the Jardin des Plantes in Paris and Scottish botanist William Aiton at Kew Gardens. That same year, John Fraser, English nurseryman and later botanical collector to the Czar of Russia, brought D. coccinea seeds from Paris to the Apothecaries Gardens in England, where they flowered in his greenhouse a year later, providing Botanical Magazine with an illustration.In 1804, a new species, Dahlia sambucifolia, was successfully grown at Holland House, Kensington. Whilst in Madrid in 1804, Lady Holland was given either dahlia seeds or tubers by Cavanilles. She sent them back to England, to Lord Holland's librarian Mr Buonaiuti at Holland House, who successfully raised the plants. A year later, Buonaiuti produced two double flowers. The plants raised in 1804 did not survive; new stock was brought from France in 1815. In 1824, Lord Holland sent his wife a note containing the following verse:
"The dahlia you brought to our isle
Your praises for ever shall speak;
Mid gardens as sweet as your smile,
And in colour as bright as your cheek."
In 1805, German naturalist Alexander von Humboldt sent more seeds from Mexico to Aiton in England, Thouin in Paris, and Christoph Friedrich Otto, director of the Berlin Botanical Garden. More significantly, he sent seeds to botanist Carl Ludwig Willdenow in Germany. Willdenow now reclassified the rapidly growing number of species, changing the genus from Dahlia to Georgina; after naturalist Johann Gottlieb Georgi. He combined the Cavanilles species D. pinnata and D. rosea under the name of Georgina variabilis; D. coccinea was still held to be a separate species, which he renamed Georgina coccinea.
CLASSIFICATION
Since 1789 when Cavanilles first flowered the dahlia in Europe, there has been an ongoing effort by many growers, botanists and taxonomists, to determine the development of the dahlia to modern times. At least 85 species have been reported: approximately 25 of these were first reported from the wild, the remainder appeared in gardens in Europe. They were considered hybrids, the results of crossing between previously reported species, or developed from the seeds sent by Humboldt from Mexico in 1805, or perhaps from some other undocumented seeds that had found their way to Europe. Several of these were soon discovered to be identical with earlier reported species, but the greatest number are new varieties. Morphological variation is highly pronounced in the dahlia. William John Cooper Lawrence, who hybridized hundreds of families of dahlias in the 1920s, stated: "I have not yet seen any two plants in the families I have raised which were not to be distinguished one from the other. Constant reclassification of the 85 reported species has resulted in a considerably smaller number of distinct species, as there is a great deal of disagreement today between systematists over classification.
In 1829, all species growing in Europe were reclassified under an all-encompassing name of D. variabilis, Desf., though this is not an accepted name. Through the interspecies cross of the Humboldt seeds and the Cavanilles species, 22 new species were reported by that year, all of which had been classified in different ways by several different taxonomists, creating considerable confusion as to which species was which.
In 1830 William Smith suggested that all dahlia species could be divided into two groups for color, red-tinged and purple-tinged. In investigating this idea Lawrence determined that with the exception of D. variabilis, all dahlia species may be assigned to one of two groups for flower-colour: Group I (ivory-magenta) or Group II (yellow-orange-scarlet).
CIRCUMSCRIPTION
The genus Dahlia is situated in the Asteroideae subfamily of the Asteraceae, in the Coreopsideae tribe. Within that tribe it is the second largest genus, after Coreopsis, and appears as a well defined clade within the Coreopsideae.
SUBDIVISION
INFRAGENERIC SUBDIVISION
Sherff (1955), in the first modern taxonomy described three sections for the 18 species he recognised, Pseudodendron, Epiphytum and Dahlia. By 1969 Sørensen recognised 29 species and four sections by splitting off Entemophyllon from section Dahlia. By contrast Giannasi (1975) using a phytochemical analysis based on flavonoids, reduced the genus to just two sections, Entemophyllon and Dahlia, the latter having three subsections, Pseudodendron, Dahlia, and Merckii. Sørensen then issued a further revision in 1980, incorporating subsection Merckii in his original section Dahlia. When he described two new species in the 1980s (Dahlia tubulata and D. congestifolia), he placed them within his existing sections. A further species, Dahlia sorensenii was added by Hansen and Hjerting in (1996). At the same time they demonstrated that Dahlia pinnata should more properly be designated D. x pinnata. D. x pinnata was shown to actually be a variant of D. sorensenii that had acquired hybrid qualities before it was introduced to Europe in the sixteenth century and formally named by Cavanilles. The original wild D. pinnata is presumed extinct. Further species continue to be described, Saar (2003) describing 35 species. However separation of the sections on morphological, cytologal and biocemical criteria has not been entirely satisfactory.
To date these sectional divisions have not been fully supported phylogenetically, which demonstrate only section Entemophyllon as a distinct sectional clade. The other major grouping is the Core Dahlia Clade (CDC), which includes most of section Dahlia. The remainder of the species occupy what has been described as the Variable Root Clade (VRC) which includes the small section Pseudodendron but also the monotypic section Epiphytum and a number of species from within section Dahlia. Outside of these three clades lie D. tubulata and D. merckii as a polytomy.
Horticulturally the sections retain some usage, section Pseudodendron being referred to as 'Tree Dahlias', Epiphytum as the 'Vine Dahlia'. The remaining two herbaceous sections being distinguished by their pinnules, opposing (Dahlia) or alternating (Entemophyllon).
SECTIONS
Sections (including chromosome numbers), with geographical distribution;
- Epiphytum Sherff (2n = 32)
10 m tall climber with aerial roots 5 cm thick and up to more than 20 m long; pinnules opposite
1 species, D. macdougallii Sherff
Mexico: Oaxaca
- Entemophyllon P. D. Sorensen (2n = 34)
6 species
Mexico: Hidalgo, Nuevo León, Tamaulipas, Querétaro, Durango, San Luis Potosí
- Pseudodendron P. D. Sorensen (2n = 32)
3 species + D. excelsa of uncertain identity
Mexico: Chiapas, Guerrero, Jalisco, Michoacan, Oaxaca, and
Costa Rica, El Salvador, Guatemala & Colombia
- Dahlia (2n = 32, 36 or 64)
24 species
Mexico: Distrito Federal, Guerrero, Hidalgo, Morelos, Nuevo León, Puebla, San Luis Potosí, Tamaulipas, Veracruz, Oaxaca, Puebla, Chiapas, México, Huehuetenango, Chihuahua, Durango, Michoacan & Guatemala
Only Pseudodendron (D. imperialis) and Dahlia (D. australis, D. coccinea) occur outside Mexico.
SPECIES
There are currently 42 accepted species in the Dahlia genus, but new species continue to be described.
ETYMOLOGY
The naming of the plant itself has long been a subject of some confusion. Many sources state that the name "Dahlia" was bestowed by the pioneering Swedish botanist and taxonomist Carl Linnaeus to honor his late student, Anders Dahl, author of Observationes Botanicae. However, Linnaeus died in 1778, more than eleven years before the plant was introduced into Europe in 1789, so while it is generally agreed that the plant was named in 1791 in honor of Dahl, who had died two years before, Linnaeus could not have been the one who did so. It was probably Abbe Antonio Jose Cavanilles, Director of the Royal Gardens of Madrid, who should be credited with the attempt to scientifically define the genus, since he not only received the first specimens from Mexico in 1789, but named the first three species that flowered from the cuttings.
Regardless of who bestowed it, the name was not so easily established. In 1805, German botanist Carl Ludwig Willdenow, asserting that the genus Dahlia Thunb. (published a year after Cavanilles's genus and now considered a synonym of Trichocladus) was more widely accepted, changed the plants' genus from Dahlia to Georgina; after the German-born naturalist Johann Gottlieb Georgi, a professor at the Imperial Academy of Sciences of St. Petersburg, Russia. He also reclassified and renamed the first three species grown, and identified, by Cavanilles. It was not until 1810, in a published article, that he officially adopted the Cavanilles' original designation of Dahlia. However, the name Georgina still persisted in Germany for the next few decades.
"Dahl" is a homophone of the Swedish word "dal", or "valley"; although it is not a true translation, the plant is sometimes referred to as the "valley flower".
DISTRIBUTION AND HABITAT
Predominantly Mexico, but some species are found ranging as far south as northern South America. D. australis occurs at least as far south as southwestern Guatemala, while D. coccinea and D. imperialis also occur in parts of Central America and northern South America. Dahlia is a genus of the uplands and mountains, being found at elevations between 1,500 and 3,700 meters, in what has been described as a "pine-oak woodland" vegetative zone. Most species have limited ranges scattered throughout many mountain ranges in Mexico.
ECOLOGY
The commonest pollinators are bees and small beetles.
PESTS AND DISEASES
Slugs and snails are serious pests in some parts of the world, particularly in spring when new growth is emerging through the soil. Earwigs can also disfigure the blooms. The other main pests likely to be encountered are aphids (usually on young stems and immature flower buds), red spider mite (causing foliage mottling and discolouration, worse in hot and dry conditions) and capsid bugs (resulting in contortion and holes at growing tips). Diseases affecting dahlias include powdery mildew, grey mould (Botrytis cinerea), verticillium wilt, dahlia smut (Entyloma calendulae f. dahliae), phytophthora and some plant viruses. Dahlias are a source of food for the larvae of some Lepidoptera species including Angle Shades, Common Swift, Ghost Moth and Large Yellow Underwing.
CULTIVATION
Dahlias grow naturally in climates which do not experience frost (the tubers are hardy to USDA Zone 8), consequently they are not adapted to withstand sub-zero temperatures. However, their tuberous nature enables them to survive periods of dormancy, and this characteristic means that gardeners in temperate climates with frosts can grow dahlias successfully, provided the tubers are lifted from the ground and stored in cool yet frost-free conditions during the winter. Planting the tubers quite deep (10 – 15 cm) also provides some protection. When in active growth, modern dahlia hybrids perform most successfully in well-watered yet free-draining soils, in situations receiving plenty of sunlight. Taller cultivars usually require some form of staking as they grow, and all garden dahlias need deadheading regularly, once flowering commences.
HORTICURAL CLASSIFICATION
HISTORY
The inappropriate term D. variabilis is often used to describe the cultivars of Dahlia since the correct parentage remains obscure, but probably involves Dahlia coccinea. In 1846 the Caledonia Horticultural Society of Edinburgh offered a prize of 2,000 pounds to the first person succeeding in producing a blue dahlia. This has to date not been accomplished. While dahlias produce anthocyanin, an element necessary for the production of the blue, to achieve a true blue color in a plant, the anthocyanin delphinidin needs six hydroxyl groups. To date dahlias have only developed five, so the closest that breeders have come to achieving a "blue" specimen are variations of mauve, purples and lilac hues.
By the beginning of the twentieth century a number of different types were recognised. These terms were based on shape or colour, and the National Dahlia Society included cactus, pompon, single, show and fancy in its 1904 guide. Many national societies developed their own classification systems until 1962 when the International Horticultural Congress agreed to develop an internationally recognised system at it Brussels meeting that year, and subsequently in Maryland in 1966. This culminated in the 1969 publication of The International Register of Dahlia Names by the Royal Horticultural Society which became the central registering authority.
This system depended primarily on the visibility of the central disc, whether it was open centred or whether only ray florets were apparent centrally (double bloom). The double bloom cultivars were then subdivided according to the way in which they were folded along their longitudinal axis, flat, involute (curled inwards) or revolute (curling backwards). If the end of the ray floret was split, they were considered fimbriated. Based on these characteristics, nine groups were defined plua a tenth miscellaneous group for any cultivars not fitting the above characteristics. Fimbriated dahlias were added in 2004, and two further groups (Single and Double orchid) in 2007. The last group to be added, Peony, first appeared in 2012.
In many cases the bloom diametre was then used to further label certain groups from miniature through to giant. This practice was abandoned in 2012.
MODERN SYSTEM (RHS)
There are now more than 57,000 registered cultivars, which are officially registered through the Royal Horticultural Society (RHS). The official register is The International Register of Dahlia Names 1969 (1995 reprint) which is updated by annual supplements. The original 1969 registry published about 14,000 cultivars adding a further 1700 by 1986 and in 2003 there were 18,000. Since then about a hundred new cultivars are added annually.
FLOWER TYPE
The official RHS classification lists fourteen groups, grouped by flower type, together with the abbreviations used by the RHS;
Group 1 – Single-flowered dahlias (Sin) — Flower has a central disc with a single outer ring of florets (which may overlap) encircling it, and which may be rounded or pointed.
Group 2 – Anemone-flowered dahlias (Anem) — The centre of the flower consists of dense elongated tubular florets, longer than the disc florets of Single dahlias, while the outer parts have one or more rings of flatter ray florets. Disc absent.
Group 3 – Collerette dahlias (Col) — Large flat florets forming a single outer ring around a central disc and which may overlap a smaller circle of florets closer to the centre, which have the appearance of a collar.
Group 4 – Waterlily dahlias (WL) — Double blooms, broad sparse curved, slightly curved or flat florets and very shallow in depth compared with other dahlias. Depth less than half the diameter of the bloom. Group 5 – Decorative dahlias (D) — Double blooms, ray florets broad, flat, involute no more than seventy five per cent of the longitudinal axis, slightly twisted and usually bluntly pointed. No visible central disc.
Group 6 – Ball dahlias (Ba)— Double blooms that are ball shaped or slightly flattened. Ray florets blunt or rounded at the tips, margins arranged spirally, involute for at least seventy five percent of the length of the florets. Larger than Pompons.
Group 7 – Pompon dahlias (Pom) — Double spherical miniature flowers made up entirely from florets that are curved inwards (involute) for their entire length (longitudinal axis), resembling a pompon.
Group 8 – Cactus dahlias (C) — Double blooms, ray florets pointed, with majority revolute (rolled) over more than fifty percent of their longitudinal axis, and straight or incurved. Narrower than Semi cactus.
Group 9 – Semi cactus dahlias (S–c)— Double blooms, very pointed ray florets, revolute for greater than twenty five percent and less than fifty percent of their longitudinal axis. Broad at the base and straight or incurved, almost spiky in appearance.
Group 10 – Miscellaneous dahlias (Misc) — not described in any other group.
Group 11 – Fimbriated dahlias (Fim) — ray florets evenly split or notched into two or more divisions, uniformly throughout the bloom, creating a fimbriated (fringed) effect. The petals may be flat, involute, revolute, straight, incurving or twisted.
Group 12 – Single Orchid (Star) dahlias (SinO) — single outer ring of florets surround a central disc. The ray florets are either involute or revolute.
Group 13 – Double Orchid dahlias (DblO) — Double blooms with triangular centres. The ray florets are narrowly lanceolate and are either involute or revolute. The central disc is absent.
Group 14 – Peony-flowered dahlias (P) — Large flowers with three or four rows of rays that are flattened and expanded and arranged irregularly. The rays surround a golden disc similar to that of Single dahlias.
FLOWER SIZE
Earlier versions of the registry subdivided some groups by flower size. Groups 4, 5, 8 and 9 were divided into five subgroups (A to E) from Giant to Miniature, and Group 6 into two subgroups, Small and Miniature. Dahlias were then described by Group and Subgroup, e.g. 5(d) ‘Ace Summer Sunset’. Some Dahlia Societies have continued this practice, but this is neither official nor standardised. As of 2013 The RHS uses two size descriptors
Dwarf Bedder (Dw.B.) — not usually exceeding 600 mm in height, e.g. 'Preston Park' (Sin/DwB)
Lilliput dahlias (Lil) — not usually exceeding 300 mm in height, with single, semi-double or double florets up to 26 mm in diameter. ("baby" or "top-mix" dahlias), e.g. 'Harvest Tiny Tot' (Misc/Lil)
Sizes can range from tiny micro dahlias with flowers less than 50mm to giants that are over 250mm in diameter. The groupings listed here are from the New Zealand Society.
Giant flowered cultivars have blooms with a diameter of over 250mm.
Large flowered cultivars have blooms with a diameter between 200mm-250mm.
Medium flowered cultivars have blooms with a diameter between 155mm-200mm.
Small flowered cultivars have blooms with a diameter between 115mm-155mm.
Miniature flowered cultivars have blooms with a diameter between 50mm-115mm.
Pompom flowered cultivars have blooms with a diameter less than 50mm.
In addition to the official classification and the terminology used by various dahlia societies, individual horticulturalists use a wide range of other descriptions, such as 'Incurved' and abbreviations in their catalogues, such as CO for Collarette.
BRANDING
Some plant growers include their brand name in the cultivar name. Thus Fides (part of the Dümmen Orange Group) in the Netherlands developed a series of cultivars which they named the Dahlinova Series, for example Dahlinova 'Carolina Burgundy'. These are Group 10 Miscellaneous in the RHS classification scheme.
DOUBLE DAHLIAS
In 1805, several new species were reported with red, purple, lilac, and pale yellow coloring, and the first true double flower was produced in Belgium. One of the more popular concepts of dahlia history, and the basis for many different interpretations and confusion, is that all the original discoveries were single flowered types, which, through hybridization and selective breeding, produced double forms. Many of the species of dahlias then, and now, have single flowered blooms. coccinea, the third dahlia to bloom in Europe, was a single. But two of the three drawings of dahlias by Dominguez, made in Mexico between 1570–77, showed definite characteristics of doubling. In the early days of the dahlia in Europe, the word "double" simply designated flowers with more than one row of petals. The greatest effort was now directed to developing improved types of double dahlias.
During the years 1805 to 1810 several people claimed to have produced a double dahlia. In 1805 Henry C. Andrews made a drawing of such a plant in the collection of Lady Holland, grown from seedlings sent that year from Madrid. Like other doubles of the time it did not resemble the doubles of today. The first modern double, or full double, appeared in Belgium; M. Donckelaar, Director of the Botanic Garden at Louvain, selected plants for that characteristic, and within a few years secured three fully double forms. By 1826 double varieties were being grown almost exclusively, and there was very little interest in the single forms. Up to this time all the so-called double dahlias had been purple, or tinged with purple, and it was doubted if a variety untinged with that color was obtainable.
In 1843, scented single forms of dahlias were first reported in Neu Verbass, Austria. D. crocea, a fragrant variety grown from one of the Humboldt seeds, was probably interbred with the single D. coccinea. A new scented species would not be introduced until the next century when the D. coronata was brought from Mexico to Germany in 1907.
The exact date the dahlia was introduced in the United States is uncertain. One of the first Dahlias in the USA may be the D. coccinea speciosissima grown by Mr William Leathe, of Cambridgeport, near Boston, around 1929. According to Edward Sayers "it attracted much admiration, and at that time was considered a very elegant flower, it was however soon eclipsed by that splendid scarlet, the Countess of Liverpool". However 9 cultivars were already listed in the catalog from Thornburn, 1825. And even earlier reference can be found in a catalogue from the Linnaean Botanical Garden, New York, 1820, that includes one scarlet, one purple, and two double orange Dahlias for sale.
Sayers stated that "No person has done more for the introduction and advancement of the culture of the Dahlia than George C. Thorburn, of New York, who yearly flowers many thousand plants at his place at Hallet's Cove, near Harlaem. The show there in the flowering season is a rich treat for the lovers of floriculture : for almost every variety can be seen growing in two large blocks or masses which lead from the road to the dwelling-house, and form a complete field of the Dahlia as a foreground to the house. Mr T. Hogg, Mr William Read, and many other well known florists, have also contributed much in the vicinity of New York, to the introduction of the Dahlia. Indeed so general has become the taste that almost every garden has its show of the Dahlia in the season." In Boston too there were many collections, a collection from the Messrs Hovey of Cambridgeport was also mentioned.
In 1835 Thomas Bridgeman, published a list of 160 double dahlias in his Florist's Guide. 60 of the choicest were supplied by Mr. G. C. Thornburn of Astoria, N.Y. who got most of them from contacts in the UK. Not a few of them had taken prices "at the English and American exhibitions".
"STARS OF DEVIL"
In 1872 J.T. van der Berg of Utrecht in the Netherlands, received a shipment of seeds and plants from a friend in Mexico. The entire shipment was badly rotted and appeared to be ruined, but van der Berg examined it carefully and found a small piece of root that seemed alive. He planted and carefully tended it; it grew into a plant that he identified as a dahlia. He made cuttings from the plant during the winter of 1872-1873. This was an entirely different type of flower, with a rich, red color and a high degree of doubling. In 1874 van der Berg catalogued it for sale, calling it Dahlia juarezii to honor Mexican President Benito Pablo Juarez, who had died the year before, and described it as "...equal to the beautiful color of the red poppy. Its form is very outstanding and different in every respect of all known dahlia flowers.".
This plant has perhaps had a greater influence on the popularity of the modern dahlia than any other. Called "Les Etoiles de Diable" (Stars of the Devil) in France and "Cactus dahlia" elsewhere, the edges of its petals rolled backwards, rather than forward, and this new form revolutionized the dahlia world. It was thought to be a distinct mutation since no other plant that resembled it could be found in the wild. Today it is assumed that D. juarezii had, at one time, existed in Mexico and subsequently disappeared. Nurserymen in Europe crossbred this plant with dahlias discovered earlier; the results became the progenitors of all modern dahlia hybrids today.
AWARD OF GARDEN MERIT (RHS)
As of 2015, 124 dahlia cultivars have gained the Royal Horticultural Society's Award of Garden Merit:
"Bednall beauty"
"Bishop of Llandaff"
"Clair de lune"
"David Howard"
"Ellen Huston"
"Fascination"
"Gallery art deco"
"Gallery Art Nouveau"
"Glorie van Heemstede"
"Honka"
"Moonfire"
"Twyning's After Eight"
USES
FLORICULTURE
The asterid eudicots contain two economically important geophyte genera, Dahlia and Liatris. Horticulturally the garden dahlia is usually treated as the cultigen D. variabilis Hort., which while being responsible for thousands of cultivars has an obscure taxonomic status.
OTHER
Today the dahlia is still considered one of the native ingredients in Oaxacan cuisine; several cultivars are still grown especially for their large, sweet potato-like tubers. Dacopa, an intense mocha-tasting extract from the roasted tubers, is used to flavor beverages throughout Central America.
In Europe and America, prior to the discovery of insulin in 1923, diabetics - as well as consumptives - were often given a substance called Atlantic starch or diabetic sugar, derived from inulin, a naturally occurring form of fruit sugar, extracted from dahlia tubers. Inulin is still used in clinical tests for kidney functionality.
WIKIPEDIA
A June day at Kew Gardens.
Fennel (Foeniculum vulgare) is a flowering plant species in the carrot family Apiaceae. It is a hardy, perennial herb with yellow flowers and feathery leaves. It is indigenous to the shores of the Mediterranean but has become widely naturalized in many parts of the world, especially on dry soils near the sea coast and on riverbanks.
It is a highly flavourful herb used in cooking and, along with the similar-tasting anise, is one of the primary ingredients of absinthe. Florence fennel or finocchio is a selection with a swollen, bulb-like stem base that is used as a vegetable.
The aromatic character of fennel derives from volatile oils imparting mixed aromas, including trans-anethole and estragole (resembling liquorice), fenchone (mint and camphor), limonene, 1-octen-3-ol (mushroom alcohol). Other phytochemicals found in fennel fruits include polyphenols, such as rosmarinic acid and luteolin, among others in minor content.
More about mushroom alcohol ...
1-Octen-3-ol, octenol for short and also known as mushroom alcohol, is a chemical that attracts biting insects such as mosquitoes. It is contained in human breath and sweat, and it is believed that insect repellent DEET works by blocking the insects' octenol odorant receptors.
The name "mushroom alcohol" for 1-octen-3-ol comes from its first isolation by S. Murahashi in 1936 and 1938 from crushed matsutake mushrooms. A recent study on volatiles of this mushroom has shown this compound is only produced upon tissue disruption. This alcohol is found in many other mushrooms where it may play a role as an antifeedant.
I want to be a good farmer and a student of Salicornia Herbacea L.
blog URL www.samphiresalt.com
info@samphiresalt.com
Basella alba is a fast-growing, soft-stemmed vine, reaching 10 metres (33 ft) in length. It is found in tropical Asia and Africa where it is widely used as a leaf vegetable. Its thick, semi-succulent, heart-shaped leaves have a mild flavour and mucilaginous texture. It is rich in vitamins A and C, iron and calcium. It has been shown to contain certain phenolic phytochemicals and it has antioxidant properties.
Source: Wikipedia
I want to be a good farmer and a student of Salicornia Herbacea L.
blog URL www.samphiresalt.com
info@samphiresalt.com
www.cnn.com/2022/11/28/health/flavonols-memory-boost-well...
Slow cognitive decline with flavonols, study says
Eating more flavonols, antioxidants found in many vegetables, fruits, tea and wine, may slow your rate of memory loss, a new study finds.
The cognitive score of people in the study who ate the most flavonols declined 0.4 units per decade more slowly than those who ate the fewest flavonols. The results held even after adjusting for other factors that can affect memory, such as age, sex and smoking, according to the study recently published in Neurology, the medical journal of the American Academy of Neurology.
“It’s exciting that our study shows making specific diet choices may lead to a slower rate of cognitive decline,” said study author Dr. Thomas Holland, an instructor in the department of internal medicine at Rush University Medical Center in Chicago, in a statement.
“Something as simple as eating more fruits and vegetables and drinking more tea is an easy way for people to take an active role in maintaining their brain health.”
Flavonols are cytoprotective, meaning they protect cells, including neurons, so it’s plausible there could be a direct impact on cognition, said Dr. David Katz, a specialist in preventive and lifestyle medicine and nutrition who was not involved in the study.
“But they are also a marker of higher intake of fruits and vegetables — which is good for the brain because it is good for every vital organ, and the organism as a whole,” Katz said in an email.
“They may also be a marker of better overall diet quality, or even greater health consciousness. People who are more health conscious may do things to preserve their cognition, or maybe being more health conscious is a by-product of better cognition.”
A huge family of phytochemicals
Plants contain over 5,000 flavonoid compounds, which play roles in producing cell growth, fighting environmental stress and attracting insects for pollination.
Flavonols, a type of flavonoid, have been shown in animal and some human studies to reduce inflammation, a major trigger for chronic disease, and are rich sources of antioxidants. Antioxidants combat free radicals, “highly unstable molecules that are naturally formed when you exercise and when your body converts food into energy,” according to the National Center for Complementary and Integrative Health, part of the National Institutes of Health.
One of the most common flavonols, quercetin, has shown promise in reducing the onset of colorectal cancer and other cancers, according to studies. Onions contain the highest levels — lower levels can be found in broccoli, blueberries, cauliflower, curly kale, leeks, spinach and strawberries.
Another common flavonol, kaempferol, appears to inhibit the growth of cancer cells while preserving and protecting normal cells. Good sources of kaempferol are onions, asparagus and berries, but the richest plant sources are spinach, kale and other green leafy vegetables, as well as herbs such as chives, dill and tarragon.
third major player is myricetin, which has been studied in rodents for blood sugar control and the reduction of tau, a protein that causes the hallmark tangles of Alzheimer’s and other dementia. Spinach and strawberries contain high levels of myricetin, but honey, black currants, grapes and other fruits, berries, vegetables, nuts and tea are also good sources.
The last group of flavonols, isorhamnetin, may protect against cardiovascular and neurovascular disease in addition to anti-tumor and anti-inflammatory benefits. Good sources of isorhamnetin are pears, olive oil, wine and tomato sauce.
You can find a full list of the flavonoid content of various fruits and vegetables here.
An older, dementia-free population
The new study asked 961 people with an average age of 81 and no signs of dementia to fill out a food questionnaire each year for seven years. In addition, the participants underwent annual cognitive and memory tests and were quizzed on their time spent being physically and mentally active.
People were divided into groups based on their daily intake of flavonols. The lowest intake was about 5 milligrams a day; the highest 15 milligrams a day — equal to about a cup of dark leafy greens, the study noted. (For comparison, the average flavonol intake in US adults is about 16 to 20 milligrams per day, according to the study.)
The study looked at the impact of the four major flavonols — kaempferol, quercetin, myricetin and isorhamnetin — on the rate of cognitive decline over the seven years.
The greatest impact was found with kaempferol: People who ate the highest amounts of foods with kaempferol showed a 0.4 units per decade slower rate of cognitive decline compared with those who ate the fewest, according to the study.
Myricetin was next: People who ate the most foods with myricetin had a 0.3 units per decade slower rate of cognitive decline compared with the lowest consuming group. People who ate the most foods with quercetin showed a 0.2 units per decade slower rate of cognitive decline.
Dietary isorhamnetin had no impact, the study found.
The jury is still out?
Despite the apparent positives, studies on the impact of flavonols on human health have been inconclusive -— mainly because many are observational and cannot show a direct cause and effect. That applies to the Neurology study as well, according to its authors.
A few randomized controlled trials — the scientific gold standard — have shown benefits associated with flavonols for controlling blood sugar in type 2 diabetes and improving cardiovascular health, according to the Linus Pauling Institute, home to the Micronutrient Information Center, an online database for nutrition information.
It’s not known whether these benefits are long term, the institute said, and no clear impact has been shown for cancer prevention or cognitive protection.
“There are other bioactives that may contribute to the observed outcomes,” Katz said. “Supplemental studies are required to isolate flavonoid effects fully.”
There’s also a downside to assuming a health impact without the necessary studies to back it up, said Dr. Christopher Gardner, a research professor of medicine and director of the Nutrition Studies Research Group at Stanford University.
“You can count on Americans wanting the benefits of plants but not wanting to eat them,” he said in an email.
“(What) if people read the headline and rush out and buy bottled (extracted) flavonols instead of eating whole plant foods, and it turns out it wasn’t just the flavonols, but the package deal of everything in those plants (instead).”
RIUM, WP Kuala Lumpur, Malaysia.
Stemona curtisii Hook.f. Stemonaceae. CN; [Malay - Akar ratus, Akar seratus, Kemili hutan, Ubi kemili (sharing name with Plectranthus rotundifolius, a Lamiaceae), Pecah kelambu, Galak tua], Stemona. The vernacular names are often interchangeable used with Stemona tuberosa presumably non-native here and also many equally conflicting names and synonyms in various reports. Native to India (Nicobar Islands), Sri Lanka, Thailand and Malesia floristic zone. In peninsular Malaysia, occurrence is widespread, often in thickets near the sea, sometimes on limestone formations. Many scientific studies done to determine its phytochemical properties, but among the natives the root has been claimed an effective aphrodisiac.
Synonym(s):
Stemona minor Hook.f.
Ref. and suggested reading:
FRIM Flora Database
www.theplantlist.org/tpl/record/kew-288271
zipcodezoo.com/Plants/S/Stemona_curtisii/
proseanet.org/prosea/e-prosea_detail.php?frt=&id=1310
wannura.wordpress.com/2010/05/17/galak-tua-stemona-curtis...
Prunella vulgaris, the common self-heal, heal-all, woundwort, heart-of-the-earth, carpenter's herb, brownwort or blue curls,[1][2][3][4] is a herbaceous plant in the mint family Lamiaceae.
Self-heal is edible:[1] the young leaves and stems can be eaten raw in salads; the plant as a whole can be boiled and eaten as a leaf vegetable; and the aerial parts of the plant can be powdered and brewed in a cold infusion to make a beverage.[1]
Description
Closeup of flowers
Prunella vulgaris grows 5–30 cm (2.0–11.8 in) high,[5] with creeping, self-rooting, tough, square, reddish stems branching at the leaf axes.[6]
The leaves are lance-shaped, serrated and reddish at the tip, about 2.5 cm (0.98 in) long and 1.5 cm (0.59 in) broad, and growing in opposite pairs down the square stem.[6] Each leaf has 3-7 veins that shoot off the middle vein to the margin. The stalks of the leaves are generally short, but can be up to 5 cm (2.0 in) long.[7]
Kleine Braunelle, Blüte.jpg
The flowers grow from a clublike, somewhat square, whirled cluster; immediately below this club is a pair of stalkless leaves standing out on either side like a collar. The flowers are two-lipped and tubular. The top lip is a purple hood, and the bottom lip is often white; it has three lobes, with the middle lobe being larger and fringed upwardly. Flowers bloom at different times depending on climate and other conditions, but mostly in summer (from June to August in the USA).[6]
Self-heal propagates both by seed and vegetatively by creeping stems that root at the nodes.[8]
Two subspecies of Prunella vulgaris have been identified: var. vulgaris and var. lanceolota. [9][10]
Range
Prunella vulgaris is a perennial herb native in Europe, Asia, Africa, and North America, and is common in most temperate climates.[1] It was introduced to many countries in the 1800s and has become invasive in the Pacific Islands, including Australia, New Zealand, and Hawaii.[1][11] In Ireland, it is generally abundant.[12][13] This herb also grows in Kashmir and is locally known as kalyuth. It is boiled in water, which used to wash and bathe in order to relieve muscle pain.[14]
Habitat
Roadsides, gardens and waste-places.[12] Woodland edges, and usually in basic and neutral soils.[6][15]
Uses
P. vulgaris var lanceolata
Prunella vulgaris is edible, and can be used in salads, soups, stews, and boiled as a pot herb.[citation needed] The Nlaka'pamux drank a cold infusion of the whole plant as a common beverage.[16]
The plant has been used by aboriginal cultures to treat various physical ailments.[17]
Phytochemicals
Phytochemicals include betulinic acid, D-camphor, D-fenchone, cyanidin, delphinidin, hyperoside, manganese, lauric acid, oleanolic acid, rosmarinic acid, myristic acid, rutin, linoleic acid, ursolic acid, beta-sitosterol, lupeol, and tannins.[18][19]
Etymology
Prunella is derived from 'Brunella', a word which is itself a derivative, taken from "die Bräune", the German name for quinsy (a type of throat inflammation), which it was historically used to cure.[20]
Vulgaris means 'usual', 'common', or 'vulgar'.[20]
Thursday 24 June, Clophill
by Andrew Green
Ten entomologists and one lichenologist enjoyed a visit for this BIG visit to the former Fuller’s Earth works
at Clophill Lakes. The site proved to have a variety of interesting habitats. Despite the weather being more
overcast than forecast there were nonetheless some good finds and the temperature picked up a little after
lunch. I was lucky to sweep a Six-belted Clearwing moth from Bird’s-foot Trefoil as I was heading back to
the car. Sue Raven found a stunning female Xiphydria camelus woodwasp close to dead willow. There
were plenty of sawfly larvae about marking the beginning of the end of the adult sawfly season and an Arge
fuscipes larva is only the second record of this species since 1982
We extend our thanks to Sue Raven for access to the site and Sue would welcome further visits from
recorders by appointment. Do get in touch if you would like to visit.
More and more people today are finding themselves becoming sensitive to fragrances or scents. Occasionally, even I will walk down the aisle of a department store or step into an elevator and my eyes will start stinging and tearing because there are certain scents to which I am “sensitive”. Perhaps your significant other may be sensitive to fragrances. Then this is the bar for you!
I have always had at least 1 or 2 special unscented bars on hand so people with fragrance sensitivities can have a decent selection and not have to settle for a grocery store plain jane soap (detergent) bar.
We have outdone ourselves this time. This bar is loaded with deeply moisturizing shea butter, aloe and goat milk.
If that isn't enough to make your toes tingle we have infused the oils in this bar with Chamomile, Calendula, Plantain, Lemon Balm and Comfrey; most of which are home grown.
Plantain, like Comfrey, contains allantoin, an anti-inflammatory phytochemical kills germs, speeds wound healing, and stimulates the growth of new skin cells.
Chamomile,reportedly smoothes out broken capillaries and blisters and improves elasticity and tissue strength.
Calendula is the miracle worker of the skin, being an all-purpose skin-healing agent.
Lemon balm has both anti-bacterial and anti-viral properties as well as said being effective against the herpes virus.
I cut the first of the extreme bars from the loaf and naturally the first thing I had to do was sniff it. I swear it has no fragrance or essential oils but it has the most lovely light scent from the herbal infusion.
Nicotiana tabacum, or cultivated tobacco, is an annually grown herbaceous plant of the genus Nicotiana. N. tabacum is the most commonly grown species in the genus Nicotiana, as the plant's leaves are commercially harvested to be processed into tobacco for human use. The plant is tropical in origin, is commonly grown throughout the world, and is often found in cultivation. It grows to heights between 1 and 2 meters (3' to 6'). Research is ongoing into its ancestry among wild Nicotiana species, but it is believed to be a hybrid of Nicotiana sylvestris, N. tomentosiformis, and possibly N. otophora.
Description
It is an annual plant that grows 1 to 3 metres (3 to 10 feet) high and is sticky hairy on all parts. The stems are thick and not very branched. The leaves can be over 50 centimetres (1 ft 8 in) long with the blades ovate to elliptical, or obovate, pointed towards the front and, at the base, run down the stem or are sessile, encompassing the stem.
The scented inflorescences are multi-branched panicles. The flower stalks are 5 to 15 millimetres (3⁄16 to 9⁄16 in) long. The calyx is 12 to 18 millimetres (1⁄2 to 11⁄16 in) and is covered with uneven 4 to 8 mm (3⁄16 to 5⁄16 in) narrow pointed calyx lobes shorter than the calyx tube. The crown is plate-shaped, the coronet is white, pink or red, the corolla tube greenish-cream, pink or red. The corolla tube has a total length of 3.5 to 4.5 cm (1+3⁄8 to 1+3⁄4 in) and is 3 to 5 mm (1⁄8 to 3⁄16 in) wide in the lower part and widens to 7 to 12 mm (1⁄4 to 1⁄2 in) in the upper part. The coronet is lobed or pentagonal. The stamens are designed unevenly and start below the center of the corolla tube. The anthers of the four longer stamens are close to the opening of the corolla tube or are slightly above it. The fifth stamen is significantly shorter than both longer pairs. The stamens have a length of 2.5 to 3.5 cm (1 to 1+3⁄8 in), significantly longer than the anthers, and are hairy at the base.
The fruit is a 1.5 to 2 cm (9⁄16 to 13⁄16 in) long capsule that is narrowly elliptical to egg-shaped. It can stand out over the chalice or be enclosed by it. The seeds are spherical or broadly elliptical and are up to 0.5 mm (1⁄64 in) long with a wavy networked surface.
Almost every part of the plant except the seed contains nicotine, but the concentration is related to different factors such as species, type of land, culture and weather conditions. The concentration of nicotine increases with the age of the plant. Tobacco leaves contain 2 to 8% nicotine combined as malate or citrate. The distribution of the nicotine in the mature plant is widely variable: 64% of the total nicotine exists in the leaves, 18% in the stem, 13% in the root, and 5% in the flowers.
Phytochemistry
Natural tobacco polysaccharides, including cellulose, have been shown to be the primary precursors of acetaldehyde in tobacco smoke. The main polyphenols contained in the tobacco leaf are rutin and chlorogenic acid. Amino acids contained include glutamic acids, asparagine, glutamine, and γ-Aminobutyric acid
Pyridine alkaloids are present in tobacco as free bases and salts. Nicotine accounts for 90–95% of the plant's pyridines with nornicotine and anatabine accounting for roughly 2.5% each. Pyridyl functional groups present in minute amounts include anabasine, myosmine, cotinine and 2, 3′-bipyridyl. Indole alkaloids are also present in leaves and stems which includes harmala alkaloids as well. Yohimbine, harmine, harmaline and ajmalicine occurs in descending order, yohimbine being highest.
The tobacco plant readily absorbs heavy metals from the surrounding soil and accumulates them in its leaves. These are readily absorbed into the user's body following smoke inhalation.
Tobacco also contains the following phytochemicals: glucosides (tabacinine, tabacine), 2,3,6-trimethyl-1,4-naphthoquinone, 2-methylquinone, 2-napthylamine, propionic acid, anthalin, anethole, acrolein, cembrene, choline, nicotelline, nicotianine, and pyrene.
Megastigmatrienone
Tobacco aroma is due to presence of different volatile compounds; megastigmatrienone being the key flavor compound in tobacco. Megastigmatrienone is used as flavour in tobacco products as well.
Megastigmatrienone, a cyclohexenone, and a carotenoid-derived aromatic compound, produces spice notes associated with wine.
Megastigmatrienone is a metabolite of Brewer's yeast.
Megastigmatrienone, as Tabanone, is manufactured by Symrise as a perfume ingredient.
Habitat and ecology
N. tabacum is a native of tropical and subtropical America, also appearing as a weed.
N. tabacum is sensitive to temperature, air, ground humidity and the type of land. Temperatures of 20–30 °C (68–86 °F) are best for adequate growth; an atmospheric humidity of 80 to 85% and soil without a high level of nitrogen are also optimal.
Parasites
The potato tuber moth (Phthorimaea operculella) is an oligophagous insect that prefers to feed on plants of the family Solanaceae such as tobacco plants. Female P. operculella use the leaves to lay their eggs and the hatched larvae will eat away at the mesophyll of the leaf.
Uses
The plant is native to the Caribbean, where the Taíno people were the first recorded peoples to use it and cultivate it. In 1560, Jean Nicot de Villemain, then French ambassador to Portugal, brought tobacco seeds and leaves as a "wonder drug" to the French court. In 1586 the botanist Jaques Dalechamps gave the plant the name of Herba nicotiana, which was also adopted by Linné. It was considered a decorative plant at first, then a panacea, before it became a common snuff and tobacco plant.
Tobacco arrived in Africa at the beginning of the 17th century. The leaf extract was a popular pest control method up to the beginning of the 20th century. In 1851, the Belgian chemist Jean Stas documented the use of tobacco extract as a murder poison. The Belgian count Hippolyte Visart de Bocarmé had poisoned his brother-in-law with tobacco leaf extract in order to acquire some urgently needed money. This was the first exact proof of alkaloids in forensic medicine.
It is now commercially cultivated worldwide. All parts of the plant contain nicotine, which can be extracted and used as an insecticide. The dried leaves can also be used; they remain effective for 6 months after drying. The juice of the leaves can be rubbed on the body as an insect repellent. The leaves can be dried and chewed as an intoxicant. The dried leaves are also used as snuff or are smoked. This is the main species that is used to make cigarettes, cigars, and other products for smokers. A drying oil is obtained from the seed.
Other varieties are cultivated as ornamental plants.
After tobacco is harvested, it is cured (dried), and then aged to improve its flavor. There are four common methods of curing tobacco: air curing, fire curing, flue curing, and sun curing. The curing method used depends on the type of tobacco and its intended use. Air-cured tobacco is sheltered from wind and sun in a well-ventilated barn, where it air dries for six to eight weeks. Air-cured tobacco is low in sugar, which gives the tobacco smoke a light, sweet flavour, and high in nicotine. Cigar and burley tobaccos are air cured.
In fire curing, smoke from a low-burning fire on the barn floor permeates the leaves. This gives the leaves a distinctive smoky aroma and flavor. Fire curing takes three to ten weeks and produces a tobacco low in sugar and high in nicotine. Pipe tobacco, chewing tobacco, and snuff are fire cured.
Flue-cured tobacco is kept in an enclosed barn heated by flues (pipes) of hot air, but the tobacco is not directly exposed to smoke. This method produces cigarette tobacco that is high in sugar and has medium to high levels of nicotine. It is the fastest method of curing, requiring about a week. Virginia tobacco that has been flue cured is also called bright tobacco, because flue curing turns its leaves gold, orange, or yellow.
Sun-cured tobacco dries uncovered in the sun. This method is used in Greece, Turkey, and other Mediterranean countries to produce oriental tobacco. Sun-cured tobacco is low in sugar and nicotine and is used in cigarettes.
Once the tobacco is cured, workers tie it into small bundles of about 20 leaves, called hands, or use a machine to make large blocks, called bales. The hands or bales are aged for one to three years to improve flavor and reduce bitterness.
Ethnomedicinal uses
The regions that have histories of use of the plant include:
Brazil: The leaf juice is taken orally to induce vomiting and narcosis.
Colombia: Fresh leaf is used as poultice over boils and infected wounds; the leaves are crushed with oil from palms and used as hair treatment to prevent baldness.
Cuba: Extract of the leaf is taken orally to treat dysmenorrhea.
East Africa: Dried leaves of Nicotiana tabacum and Securinega virosa are mixed into a paste and used externally to destroy worms in sores.
Ecuador: Leaf juice is used for indisposition, chills and snake bites and to treat pulmonary ailments.
Fiji: Fresh root is taken orally for asthma and indigestion; fresh root is applied ophthalmically as drops for bloodshot eyes and other problems; seed is taken orally for rheumatism and to treat hoarseness.
Guatemala: Leaves are applied externally by adults for myiasis, headache and wounds; hot water extract of the dried leaf is applied externally for ring worms, fungal diseases of the skin, wounds, ulcers, bruises, sores, mouth lesions, stomatitis and mucosa; leaf is orally taken for kidney diseases.
Haiti: Decoction of dried leaf is taken orally for bronchitis and pneumonia.
Hong Kong: Fresh leaves are mashed and combined with vegetable oil to create a potion that is applied to injuries for it to heal faster. This practice is also apparent in other places in China.
Iran: Infusion of the dried leaf is applied externally as an insect repellent; ointments made from crushed leaves are used for baldness, dermatitis and infectious ulceration and as a pediculicide.
Mexico (south-eastern): Among the ancient Maya, Nicotiana was considered a sacred plant, closely associated with deities of earth and sky, and used for both visionary and therapeutic ends. The contemporary Tzeltal and Tzotzil Maya of Highland Chiapas (Mexico) are bearers of this ethnobotanical inheritance, preserving a rich and varied tradition of Nicotiana use and folklore. The entire tobacco plant is viewed as a primordial medicine and a powerful botanical "helper" or "protector". Depending on the condition to be treated, whole Nicotiana leaves are used alone or in combination with other herbs in the preparation of various medicinal plasters and teas. In its most common form, fresh or ‘‘green’’ leaves are ground with slaked lime to produce an intoxicating oral snuff that serves as both a protective and therapeutic agent.
United States: Extract of N. tabacum is taken orally to treat tiredness, ward off diseases, and quiet fear.
Tanzania: Leaves of Nicotiana tabacum are placed in the vagina to stimulate labour.
Zimbabwe: Leaves or root of the plant are infused and taken by mouth for asthma and other respiratory problems. Leaves and roots are also rubbed against warts and wounds as ointment
While at the market this afternoon, Jersey Shore Fightin’ Texas Aggie Ring noticed that they had some beautiful horseradish (Armoracia Rusticana) on display so he told me to get him some. Supposedly, there are a number of health benefits of horseradish including nutritional content and phytochemicals (whatever the hell that is). It’s also high in antioxidants.
“I don’t know about all of those big words.” said Aggie Ring. “All I know is I likes me some on lots of stuff.”
Aggie Ring peeled and cut his horseradish into small cubes. Then, he put it into his enormous food processor with some vinegar, sugar and salt and “let ‘er rip!”
Once the horseradish was all chopped up, Aggie Ring took the top off of his enormous food processor and was quite taken aback by the strong pungent smell of the prepared horseradish. Aggie Ring’s eyes watered up and he had to struggle to catch his breath.
“I’m ok,” said Aggie Ring. “It’s a good burn.”
As we were transferring the horseradish into a container to store it, Aggie Ring said, “That was pretty damn easy. Why doesn’t everyone make their own horseradish?”
#AggieRing
Dahlia (UK /deɪliə/ or US /dɑːliə/) is a genus of bushy, tuberous, herbaceous perennial plants native to Mexico. A member of the Asteraceae (or Compositae), dicotyledonous plants, related species include the sunflower, daisy, chrysanthemum, and zinnia. There are 42 species of dahlia, with hybrids commonly grown as garden plants. Flower forms are variable, with one head per stem; these can be as small as 5.1 cm diameter or up to 30 cm ("dinner plate"). This great variety results from dahlias being octoploids—that is, they have eight sets of homologous chromosomes, whereas most plants have only two. In addition, dahlias also contain many transposons - genetic pieces that move from place to place upon an allele - which contributes to their manifesting such great diversity.
The stems are leafy, ranging in height from as low as 30 cm to more than 1.8–2.4 m. The majority of species do not produce scented flowers or cultivars. Like most plants that do not attract pollinating insects through scent, they are brightly colored, displaying most hues, with the exception of blue.
The dahlia was declared the national flower of Mexico in 1963. The tubers were grown as a food crop by the Aztecs, but this use largely died out after the Spanish Conquest. Attempts to introduce the tubers as a food crop in Europe were unsuccessful.
DESCRIPTION
Perennial plants, with mostly tuberous roots. While some have herbaceous stems, others have stems which lignify in the absence of secondary tissue and resprout following winter dormancy, allowing further seasons of growth. as a member of the Asteraceae the flower head is actually a composite (hence the older name Compositae) with both central disc florets and surrounding ray florets. Each floret is a flower in its own right, but is often incorrectly described as a petal, particularly by horticulturalists. The modern mame Asteraceae refers to the appearance of a star with surrounding rays.
TAXONOMY
HISTORY
EARLY HISTORY
Spaniards reported finding the plants growing in Mexico in 1525, but the earliest known description is by Francisco Hernández, physician to Philip II, who was ordered to visit Mexico in 1570 to study the "natural products of that country". They were used as a source of food by the indigenous peoples, and were both gathered in the wild and cultivated. The Aztecs used them to treat epilepsy, and employed the long hollow stem of the (Dahlia imperalis) for water pipes. The indigenous peoples variously identified the plants as "Chichipatl" (Toltecs) and "Acocotle" or "Cocoxochitl" (Aztecs). From Hernandez' perception of Aztec, to Spanish, through various other translations, the word is "water cane", "water pipe", "water pipe flower", "hollow stem flower" and "cane flower". All these refer to the hollowness of the plants' stem.Hernandez described two varieties of dahlias (the pinwheel-like Dahlia pinnata and the huge Dahlia imperialis) as well as other medicinal plants of New Spain. Francisco Dominguez, a Hidalgo gentleman who accompanied Hernandez on part of his seven-year study, made a series of drawings to supplement the four volume report. Three of his drawings showed plants with flowers: two resembled the modern bedding dahlia, and one resembled the species Dahlia merki; all displayed a high degree of doubleness. In 1578 the manuscript, entitled Nova Plantarum, Animalium et Mineralium Mexicanorum Historia, was sent back to the Escorial in Madrid; they were not translated into Latin by Francisco Ximenes until 1615. In 1640, Francisco Cesi, President of the Academia Linei of Rome, bought the Ximenes translation, and after annotating it, published it in 1649-1651 in two volumes as Rerum Medicarum Novae Hispaniae Thesaurus Seu Nova Plantarium, Animalium et Mineraliuím Mexicanorum Historia. The original manuscripts were destroyed in a fire in the mid-1600s.
EUROPEAN INTRODUCTION
In 1787, the French botanist Nicolas-Joseph Thiéry de Menonville, sent to Mexico to steal the cochineal insect valued for its scarlet dye, reported the strangely beautiful flowers he had seen growing in a garden in Oaxaca. In 1789, Vicente Cervantes, Director of the Botanical Garden at Mexico City, sent "plant parts" to Abbe Antonio José Cavanilles, Director of the Royal Gardens of Madrid. Cavanilles flowered one plant that same year, then the second one a year later. In 1791 he called the new growths "Dahlia" for Anders Dahl. The first plant was called Dahlia pinnata after its pinnate foliage; the second, Dahlia rosea for its rose-purple color. In 1796 Cavanilles flowered a third plant from the parts sent by Cervantes, which he named Dahlia coccinea for its scarlet color.In 1798, Cavanilles sent D. Pinnata seeds to Parma, Italy. That year, the Marchioness of Bute, wife of The Earl of Bute, the English Ambassador to Spain, obtained a few seeds from Cavanilles and sent them to Kew Gardens, where they flowered but were lost after two to three years. In the following years Madrid sent seeds to Berlin and Dresden in Germany, and to Turin and Thiene in Italy. In 1802, Cavanilles sent tubers of "these three" (D. pinnata, D. rosea, D. coccinea) to Swiss botanist Augustin Pyramus de Candolle at University of Montpelier in France, Andre Thouin at the Jardin des Plantes in Paris and Scottish botanist William Aiton at Kew Gardens. That same year, John Fraser, English nurseryman and later botanical collector to the Czar of Russia, brought D. coccinea seeds from Paris to the Apothecaries Gardens in England, where they flowered in his greenhouse a year later, providing Botanical Magazine with an illustration.In 1804, a new species, Dahlia sambucifolia, was successfully grown at Holland House, Kensington. Whilst in Madrid in 1804, Lady Holland was given either dahlia seeds or tubers by Cavanilles. She sent them back to England, to Lord Holland's librarian Mr Buonaiuti at Holland House, who successfully raised the plants. A year later, Buonaiuti produced two double flowers. The plants raised in 1804 did not survive; new stock was brought from France in 1815. In 1824, Lord Holland sent his wife a note containing the following verse:
"The dahlia you brought to our isle
Your praises for ever shall speak;
Mid gardens as sweet as your smile,
And in colour as bright as your cheek."
In 1805, German naturalist Alexander von Humboldt sent more seeds from Mexico to Aiton in England, Thouin in Paris, and Christoph Friedrich Otto, director of the Berlin Botanical Garden. More significantly, he sent seeds to botanist Carl Ludwig Willdenow in Germany. Willdenow now reclassified the rapidly growing number of species, changing the genus from Dahlia to Georgina; after naturalist Johann Gottlieb Georgi. He combined the Cavanilles species D. pinnata and D. rosea under the name of Georgina variabilis; D. coccinea was still held to be a separate species, which he renamed Georgina coccinea.
CLASSIFICATION
Since 1789 when Cavanilles first flowered the dahlia in Europe, there has been an ongoing effort by many growers, botanists and taxonomists, to determine the development of the dahlia to modern times. At least 85 species have been reported: approximately 25 of these were first reported from the wild, the remainder appeared in gardens in Europe. They were considered hybrids, the results of crossing between previously reported species, or developed from the seeds sent by Humboldt from Mexico in 1805, or perhaps from some other undocumented seeds that had found their way to Europe. Several of these were soon discovered to be identical with earlier reported species, but the greatest number are new varieties. Morphological variation is highly pronounced in the dahlia. William John Cooper Lawrence, who hybridized hundreds of families of dahlias in the 1920s, stated: "I have not yet seen any two plants in the families I have raised which were not to be distinguished one from the other. Constant reclassification of the 85 reported species has resulted in a considerably smaller number of distinct species, as there is a great deal of disagreement today between systematists over classification.
In 1829, all species growing in Europe were reclassified under an all-encompassing name of D. variabilis, Desf., though this is not an accepted name. Through the interspecies cross of the Humboldt seeds and the Cavanilles species, 22 new species were reported by that year, all of which had been classified in different ways by several different taxonomists, creating considerable confusion as to which species was which.
In 1830 William Smith suggested that all dahlia species could be divided into two groups for color, red-tinged and purple-tinged. In investigating this idea Lawrence determined that with the exception of D. variabilis, all dahlia species may be assigned to one of two groups for flower-colour: Group I (ivory-magenta) or Group II (yellow-orange-scarlet).
CIRCUMSCRIPTION
The genus Dahlia is situated in the Asteroideae subfamily of the Asteraceae, in the Coreopsideae tribe. Within that tribe it is the second largest genus, after Coreopsis, and appears as a well defined clade within the Coreopsideae.
SUBDIVISION
INFRAGENERIC SUBDIVISION
Sherff (1955), in the first modern taxonomy described three sections for the 18 species he recognised, Pseudodendron, Epiphytum and Dahlia. By 1969 Sørensen recognised 29 species and four sections by splitting off Entemophyllon from section Dahlia. By contrast Giannasi (1975) using a phytochemical analysis based on flavonoids, reduced the genus to just two sections, Entemophyllon and Dahlia, the latter having three subsections, Pseudodendron, Dahlia, and Merckii. Sørensen then issued a further revision in 1980, incorporating subsection Merckii in his original section Dahlia. When he described two new species in the 1980s (Dahlia tubulata and D. congestifolia), he placed them within his existing sections. A further species, Dahlia sorensenii was added by Hansen and Hjerting in (1996). At the same time they demonstrated that Dahlia pinnata should more properly be designated D. x pinnata. D. x pinnata was shown to actually be a variant of D. sorensenii that had acquired hybrid qualities before it was introduced to Europe in the sixteenth century and formally named by Cavanilles. The original wild D. pinnata is presumed extinct. Further species continue to be described, Saar (2003) describing 35 species. However separation of the sections on morphological, cytologal and biocemical criteria has not been entirely satisfactory.
To date these sectional divisions have not been fully supported phylogenetically, which demonstrate only section Entemophyllon as a distinct sectional clade. The other major grouping is the Core Dahlia Clade (CDC), which includes most of section Dahlia. The remainder of the species occupy what has been described as the Variable Root Clade (VRC) which includes the small section Pseudodendron but also the monotypic section Epiphytum and a number of species from within section Dahlia. Outside of these three clades lie D. tubulata and D. merckii as a polytomy.
Horticulturally the sections retain some usage, section Pseudodendron being referred to as 'Tree Dahlias', Epiphytum as the 'Vine Dahlia'. The remaining two herbaceous sections being distinguished by their pinnules, opposing (Dahlia) or alternating (Entemophyllon).
SECTIONS
Sections (including chromosome numbers), with geographical distribution;
- Epiphytum Sherff (2n = 32)
10 m tall climber with aerial roots 5 cm thick and up to more than 20 m long; pinnules opposite
1 species, D. macdougallii Sherff
Mexico: Oaxaca
- Entemophyllon P. D. Sorensen (2n = 34)
6 species
Mexico: Hidalgo, Nuevo León, Tamaulipas, Querétaro, Durango, San Luis Potosí
- Pseudodendron P. D. Sorensen (2n = 32)
3 species + D. excelsa of uncertain identity
Mexico: Chiapas, Guerrero, Jalisco, Michoacan, Oaxaca, and
Costa Rica, El Salvador, Guatemala & Colombia
- Dahlia (2n = 32, 36 or 64)
24 species
Mexico: Distrito Federal, Guerrero, Hidalgo, Morelos, Nuevo León, Puebla, San Luis Potosí, Tamaulipas, Veracruz, Oaxaca, Puebla, Chiapas, México, Huehuetenango, Chihuahua, Durango, Michoacan & Guatemala
Only Pseudodendron (D. imperialis) and Dahlia (D. australis, D. coccinea) occur outside Mexico.
SPECIES
There are currently 42 accepted species in the Dahlia genus, but new species continue to be described.
ETYMOLOGY
The naming of the plant itself has long been a subject of some confusion. Many sources state that the name "Dahlia" was bestowed by the pioneering Swedish botanist and taxonomist Carl Linnaeus to honor his late student, Anders Dahl, author of Observationes Botanicae. However, Linnaeus died in 1778, more than eleven years before the plant was introduced into Europe in 1789, so while it is generally agreed that the plant was named in 1791 in honor of Dahl, who had died two years before, Linnaeus could not have been the one who did so. It was probably Abbe Antonio Jose Cavanilles, Director of the Royal Gardens of Madrid, who should be credited with the attempt to scientifically define the genus, since he not only received the first specimens from Mexico in 1789, but named the first three species that flowered from the cuttings.
Regardless of who bestowed it, the name was not so easily established. In 1805, German botanist Carl Ludwig Willdenow, asserting that the genus Dahlia Thunb. (published a year after Cavanilles's genus and now considered a synonym of Trichocladus) was more widely accepted, changed the plants' genus from Dahlia to Georgina; after the German-born naturalist Johann Gottlieb Georgi, a professor at the Imperial Academy of Sciences of St. Petersburg, Russia. He also reclassified and renamed the first three species grown, and identified, by Cavanilles. It was not until 1810, in a published article, that he officially adopted the Cavanilles' original designation of Dahlia. However, the name Georgina still persisted in Germany for the next few decades.
"Dahl" is a homophone of the Swedish word "dal", or "valley"; although it is not a true translation, the plant is sometimes referred to as the "valley flower".
DISTRIBUTION AND HABITAT
Predominantly Mexico, but some species are found ranging as far south as northern South America. D. australis occurs at least as far south as southwestern Guatemala, while D. coccinea and D. imperialis also occur in parts of Central America and northern South America. Dahlia is a genus of the uplands and mountains, being found at elevations between 1,500 and 3,700 meters, in what has been described as a "pine-oak woodland" vegetative zone. Most species have limited ranges scattered throughout many mountain ranges in Mexico.
ECOLOGY
The commonest pollinators are bees and small beetles.
PESTS AND DISEASES
Slugs and snails are serious pests in some parts of the world, particularly in spring when new growth is emerging through the soil. Earwigs can also disfigure the blooms. The other main pests likely to be encountered are aphids (usually on young stems and immature flower buds), red spider mite (causing foliage mottling and discolouration, worse in hot and dry conditions) and capsid bugs (resulting in contortion and holes at growing tips). Diseases affecting dahlias include powdery mildew, grey mould (Botrytis cinerea), verticillium wilt, dahlia smut (Entyloma calendulae f. dahliae), phytophthora and some plant viruses. Dahlias are a source of food for the larvae of some Lepidoptera species including Angle Shades, Common Swift, Ghost Moth and Large Yellow Underwing.
CULTIVATION
Dahlias grow naturally in climates which do not experience frost (the tubers are hardy to USDA Zone 8), consequently they are not adapted to withstand sub-zero temperatures. However, their tuberous nature enables them to survive periods of dormancy, and this characteristic means that gardeners in temperate climates with frosts can grow dahlias successfully, provided the tubers are lifted from the ground and stored in cool yet frost-free conditions during the winter. Planting the tubers quite deep (10 – 15 cm) also provides some protection. When in active growth, modern dahlia hybrids perform most successfully in well-watered yet free-draining soils, in situations receiving plenty of sunlight. Taller cultivars usually require some form of staking as they grow, and all garden dahlias need deadheading regularly, once flowering commences.
HORTICURAL CLASSIFICATION
HISTORY
The inappropriate term D. variabilis is often used to describe the cultivars of Dahlia since the correct parentage remains obscure, but probably involves Dahlia coccinea. In 1846 the Caledonia Horticultural Society of Edinburgh offered a prize of 2,000 pounds to the first person succeeding in producing a blue dahlia. This has to date not been accomplished. While dahlias produce anthocyanin, an element necessary for the production of the blue, to achieve a true blue color in a plant, the anthocyanin delphinidin needs six hydroxyl groups. To date dahlias have only developed five, so the closest that breeders have come to achieving a "blue" specimen are variations of mauve, purples and lilac hues.
By the beginning of the twentieth century a number of different types were recognised. These terms were based on shape or colour, and the National Dahlia Society included cactus, pompon, single, show and fancy in its 1904 guide. Many national societies developed their own classification systems until 1962 when the International Horticultural Congress agreed to develop an internationally recognised system at it Brussels meeting that year, and subsequently in Maryland in 1966. This culminated in the 1969 publication of The International Register of Dahlia Names by the Royal Horticultural Society which became the central registering authority.
This system depended primarily on the visibility of the central disc, whether it was open centred or whether only ray florets were apparent centrally (double bloom). The double bloom cultivars were then subdivided according to the way in which they were folded along their longitudinal axis, flat, involute (curled inwards) or revolute (curling backwards). If the end of the ray floret was split, they were considered fimbriated. Based on these characteristics, nine groups were defined plua a tenth miscellaneous group for any cultivars not fitting the above characteristics. Fimbriated dahlias were added in 2004, and two further groups (Single and Double orchid) in 2007. The last group to be added, Peony, first appeared in 2012.
In many cases the bloom diametre was then used to further label certain groups from miniature through to giant. This practice was abandoned in 2012.
MODERN SYSTEM (RHS)
There are now more than 57,000 registered cultivars, which are officially registered through the Royal Horticultural Society (RHS). The official register is The International Register of Dahlia Names 1969 (1995 reprint) which is updated by annual supplements. The original 1969 registry published about 14,000 cultivars adding a further 1700 by 1986 and in 2003 there were 18,000. Since then about a hundred new cultivars are added annually.
FLOWER TYPE
The official RHS classification lists fourteen groups, grouped by flower type, together with the abbreviations used by the RHS;
Group 1 – Single-flowered dahlias (Sin) — Flower has a central disc with a single outer ring of florets (which may overlap) encircling it, and which may be rounded or pointed.
Group 2 – Anemone-flowered dahlias (Anem) — The centre of the flower consists of dense elongated tubular florets, longer than the disc florets of Single dahlias, while the outer parts have one or more rings of flatter ray florets. Disc absent.
Group 3 – Collerette dahlias (Col) — Large flat florets forming a single outer ring around a central disc and which may overlap a smaller circle of florets closer to the centre, which have the appearance of a collar.
Group 4 – Waterlily dahlias (WL) — Double blooms, broad sparse curved, slightly curved or flat florets and very shallow in depth compared with other dahlias. Depth less than half the diameter of the bloom. Group 5 – Decorative dahlias (D) — Double blooms, ray florets broad, flat, involute no more than seventy five per cent of the longitudinal axis, slightly twisted and usually bluntly pointed. No visible central disc.
Group 6 – Ball dahlias (Ba)— Double blooms that are ball shaped or slightly flattened. Ray florets blunt or rounded at the tips, margins arranged spirally, involute for at least seventy five percent of the length of the florets. Larger than Pompons.
Group 7 – Pompon dahlias (Pom) — Double spherical miniature flowers made up entirely from florets that are curved inwards (involute) for their entire length (longitudinal axis), resembling a pompon.
Group 8 – Cactus dahlias (C) — Double blooms, ray florets pointed, with majority revolute (rolled) over more than fifty percent of their longitudinal axis, and straight or incurved. Narrower than Semi cactus.
Group 9 – Semi cactus dahlias (S–c)— Double blooms, very pointed ray florets, revolute for greater than twenty five percent and less than fifty percent of their longitudinal axis. Broad at the base and straight or incurved, almost spiky in appearance.
Group 10 – Miscellaneous dahlias (Misc) — not described in any other group.
Group 11 – Fimbriated dahlias (Fim) — ray florets evenly split or notched into two or more divisions, uniformly throughout the bloom, creating a fimbriated (fringed) effect. The petals may be flat, involute, revolute, straight, incurving or twisted.
Group 12 – Single Orchid (Star) dahlias (SinO) — single outer ring of florets surround a central disc. The ray florets are either involute or revolute.
Group 13 – Double Orchid dahlias (DblO) — Double blooms with triangular centres. The ray florets are narrowly lanceolate and are either involute or revolute. The central disc is absent.
Group 14 – Peony-flowered dahlias (P) — Large flowers with three or four rows of rays that are flattened and expanded and arranged irregularly. The rays surround a golden disc similar to that of Single dahlias.
FLOWER SIZE
Earlier versions of the registry subdivided some groups by flower size. Groups 4, 5, 8 and 9 were divided into five subgroups (A to E) from Giant to Miniature, and Group 6 into two subgroups, Small and Miniature. Dahlias were then described by Group and Subgroup, e.g. 5(d) ‘Ace Summer Sunset’. Some Dahlia Societies have continued this practice, but this is neither official nor standardised. As of 2013 The RHS uses two size descriptors
Dwarf Bedder (Dw.B.) — not usually exceeding 600 mm in height, e.g. 'Preston Park' (Sin/DwB)
Lilliput dahlias (Lil) — not usually exceeding 300 mm in height, with single, semi-double or double florets up to 26 mm in diameter. ("baby" or "top-mix" dahlias), e.g. 'Harvest Tiny Tot' (Misc/Lil)
Sizes can range from tiny micro dahlias with flowers less than 50mm to giants that are over 250mm in diameter. The groupings listed here are from the New Zealand Society.
Giant flowered cultivars have blooms with a diameter of over 250mm.
Large flowered cultivars have blooms with a diameter between 200mm-250mm.
Medium flowered cultivars have blooms with a diameter between 155mm-200mm.
Small flowered cultivars have blooms with a diameter between 115mm-155mm.
Miniature flowered cultivars have blooms with a diameter between 50mm-115mm.
Pompom flowered cultivars have blooms with a diameter less than 50mm.
In addition to the official classification and the terminology used by various dahlia societies, individual horticulturalists use a wide range of other descriptions, such as 'Incurved' and abbreviations in their catalogues, such as CO for Collarette.
BRANDING
Some plant growers include their brand name in the cultivar name. Thus Fides (part of the Dümmen Orange Group) in the Netherlands developed a series of cultivars which they named the Dahlinova Series, for example Dahlinova 'Carolina Burgundy'. These are Group 10 Miscellaneous in the RHS classification scheme.
DOUBLE DAHLIAS
In 1805, several new species were reported with red, purple, lilac, and pale yellow coloring, and the first true double flower was produced in Belgium. One of the more popular concepts of dahlia history, and the basis for many different interpretations and confusion, is that all the original discoveries were single flowered types, which, through hybridization and selective breeding, produced double forms. Many of the species of dahlias then, and now, have single flowered blooms. coccinea, the third dahlia to bloom in Europe, was a single. But two of the three drawings of dahlias by Dominguez, made in Mexico between 1570–77, showed definite characteristics of doubling. In the early days of the dahlia in Europe, the word "double" simply designated flowers with more than one row of petals. The greatest effort was now directed to developing improved types of double dahlias.
During the years 1805 to 1810 several people claimed to have produced a double dahlia. In 1805 Henry C. Andrews made a drawing of such a plant in the collection of Lady Holland, grown from seedlings sent that year from Madrid. Like other doubles of the time it did not resemble the doubles of today. The first modern double, or full double, appeared in Belgium; M. Donckelaar, Director of the Botanic Garden at Louvain, selected plants for that characteristic, and within a few years secured three fully double forms. By 1826 double varieties were being grown almost exclusively, and there was very little interest in the single forms. Up to this time all the so-called double dahlias had been purple, or tinged with purple, and it was doubted if a variety untinged with that color was obtainable.
In 1843, scented single forms of dahlias were first reported in Neu Verbass, Austria. D. crocea, a fragrant variety grown from one of the Humboldt seeds, was probably interbred with the single D. coccinea. A new scented species would not be introduced until the next century when the D. coronata was brought from Mexico to Germany in 1907.
The exact date the dahlia was introduced in the United States is uncertain. One of the first Dahlias in the USA may be the D. coccinea speciosissima grown by Mr William Leathe, of Cambridgeport, near Boston, around 1929. According to Edward Sayers "it attracted much admiration, and at that time was considered a very elegant flower, it was however soon eclipsed by that splendid scarlet, the Countess of Liverpool". However 9 cultivars were already listed in the catalog from Thornburn, 1825. And even earlier reference can be found in a catalogue from the Linnaean Botanical Garden, New York, 1820, that includes one scarlet, one purple, and two double orange Dahlias for sale.
Sayers stated that "No person has done more for the introduction and advancement of the culture of the Dahlia than George C. Thorburn, of New York, who yearly flowers many thousand plants at his place at Hallet's Cove, near Harlaem. The show there in the flowering season is a rich treat for the lovers of floriculture : for almost every variety can be seen growing in two large blocks or masses which lead from the road to the dwelling-house, and form a complete field of the Dahlia as a foreground to the house. Mr T. Hogg, Mr William Read, and many other well known florists, have also contributed much in the vicinity of New York, to the introduction of the Dahlia. Indeed so general has become the taste that almost every garden has its show of the Dahlia in the season." In Boston too there were many collections, a collection from the Messrs Hovey of Cambridgeport was also mentioned.
In 1835 Thomas Bridgeman, published a list of 160 double dahlias in his Florist's Guide. 60 of the choicest were supplied by Mr. G. C. Thornburn of Astoria, N.Y. who got most of them from contacts in the UK. Not a few of them had taken prices "at the English and American exhibitions".
"STARS OF DEVIL"
In 1872 J.T. van der Berg of Utrecht in the Netherlands, received a shipment of seeds and plants from a friend in Mexico. The entire shipment was badly rotted and appeared to be ruined, but van der Berg examined it carefully and found a small piece of root that seemed alive. He planted and carefully tended it; it grew into a plant that he identified as a dahlia. He made cuttings from the plant during the winter of 1872-1873. This was an entirely different type of flower, with a rich, red color and a high degree of doubling. In 1874 van der Berg catalogued it for sale, calling it Dahlia juarezii to honor Mexican President Benito Pablo Juarez, who had died the year before, and described it as "...equal to the beautiful color of the red poppy. Its form is very outstanding and different in every respect of all known dahlia flowers.".
This plant has perhaps had a greater influence on the popularity of the modern dahlia than any other. Called "Les Etoiles de Diable" (Stars of the Devil) in France and "Cactus dahlia" elsewhere, the edges of its petals rolled backwards, rather than forward, and this new form revolutionized the dahlia world. It was thought to be a distinct mutation since no other plant that resembled it could be found in the wild. Today it is assumed that D. juarezii had, at one time, existed in Mexico and subsequently disappeared. Nurserymen in Europe crossbred this plant with dahlias discovered earlier; the results became the progenitors of all modern dahlia hybrids today.
AWARD OF GARDEN MERIT (RHS)
As of 2015, 124 dahlia cultivars have gained the Royal Horticultural Society's Award of Garden Merit:
"Bednall beauty"
"Bishop of Llandaff"
"Clair de lune"
"David Howard"
"Ellen Huston"
"Fascination"
"Gallery art deco"
"Gallery Art Nouveau"
"Glorie van Heemstede"
"Honka"
"Moonfire"
"Twyning's After Eight"
USES
FLORICULTURE
The asterid eudicots contain two economically important geophyte genera, Dahlia and Liatris. Horticulturally the garden dahlia is usually treated as the cultigen D. variabilis Hort., which while being responsible for thousands of cultivars has an obscure taxonomic status.
OTHER
Today the dahlia is still considered one of the native ingredients in Oaxacan cuisine; several cultivars are still grown especially for their large, sweet potato-like tubers. Dacopa, an intense mocha-tasting extract from the roasted tubers, is used to flavor beverages throughout Central America.
In Europe and America, prior to the discovery of insulin in 1923, diabetics - as well as consumptives - were often given a substance called Atlantic starch or diabetic sugar, derived from inulin, a naturally occurring form of fruit sugar, extracted from dahlia tubers. Inulin is still used in clinical tests for kidney functionality.
WIKIPEDIA
Dahlia (UK /deɪliə/ or US /dɑːliə/) is a genus of bushy, tuberous, herbaceous perennial plants native to Mexico. A member of the Asteraceae (or Compositae), dicotyledonous plants, related species include the sunflower, daisy, chrysanthemum, and zinnia. There are 42 species of dahlia, with hybrids commonly grown as garden plants. Flower forms are variable, with one head per stem; these can be as small as 5.1 cm diameter or up to 30 cm ("dinner plate"). This great variety results from dahlias being octoploids—that is, they have eight sets of homologous chromosomes, whereas most plants have only two. In addition, dahlias also contain many transposons - genetic pieces that move from place to place upon an allele - which contributes to their manifesting such great diversity.
The stems are leafy, ranging in height from as low as 30 cm to more than 1.8–2.4 m. The majority of species do not produce scented flowers or cultivars. Like most plants that do not attract pollinating insects through scent, they are brightly colored, displaying most hues, with the exception of blue.
The dahlia was declared the national flower of Mexico in 1963. The tubers were grown as a food crop by the Aztecs, but this use largely died out after the Spanish Conquest. Attempts to introduce the tubers as a food crop in Europe were unsuccessful.
DESCRIPTION
Perennial plants, with mostly tuberous roots. While some have herbaceous stems, others have stems which lignify in the absence of secondary tissue and resprout following winter dormancy, allowing further seasons of growth. as a member of the Asteraceae the flower head is actually a composite (hence the older name Compositae) with both central disc florets and surrounding ray florets. Each floret is a flower in its own right, but is often incorrectly described as a petal, particularly by horticulturalists. The modern mame Asteraceae refers to the appearance of a star with surrounding rays.
TAXONOMY
HISTORY
EARLY HISTORY
Spaniards reported finding the plants growing in Mexico in 1525, but the earliest known description is by Francisco Hernández, physician to Philip II, who was ordered to visit Mexico in 1570 to study the "natural products of that country". They were used as a source of food by the indigenous peoples, and were both gathered in the wild and cultivated. The Aztecs used them to treat epilepsy, and employed the long hollow stem of the (Dahlia imperalis) for water pipes. The indigenous peoples variously identified the plants as "Chichipatl" (Toltecs) and "Acocotle" or "Cocoxochitl" (Aztecs). From Hernandez' perception of Aztec, to Spanish, through various other translations, the word is "water cane", "water pipe", "water pipe flower", "hollow stem flower" and "cane flower". All these refer to the hollowness of the plants' stem.Hernandez described two varieties of dahlias (the pinwheel-like Dahlia pinnata and the huge Dahlia imperialis) as well as other medicinal plants of New Spain. Francisco Dominguez, a Hidalgo gentleman who accompanied Hernandez on part of his seven-year study, made a series of drawings to supplement the four volume report. Three of his drawings showed plants with flowers: two resembled the modern bedding dahlia, and one resembled the species Dahlia merki; all displayed a high degree of doubleness. In 1578 the manuscript, entitled Nova Plantarum, Animalium et Mineralium Mexicanorum Historia, was sent back to the Escorial in Madrid; they were not translated into Latin by Francisco Ximenes until 1615. In 1640, Francisco Cesi, President of the Academia Linei of Rome, bought the Ximenes translation, and after annotating it, published it in 1649-1651 in two volumes as Rerum Medicarum Novae Hispaniae Thesaurus Seu Nova Plantarium, Animalium et Mineraliuím Mexicanorum Historia. The original manuscripts were destroyed in a fire in the mid-1600s.
EUROPEAN INTRODUCTION
In 1787, the French botanist Nicolas-Joseph Thiéry de Menonville, sent to Mexico to steal the cochineal insect valued for its scarlet dye, reported the strangely beautiful flowers he had seen growing in a garden in Oaxaca. In 1789, Vicente Cervantes, Director of the Botanical Garden at Mexico City, sent "plant parts" to Abbe Antonio José Cavanilles, Director of the Royal Gardens of Madrid. Cavanilles flowered one plant that same year, then the second one a year later. In 1791 he called the new growths "Dahlia" for Anders Dahl. The first plant was called Dahlia pinnata after its pinnate foliage; the second, Dahlia rosea for its rose-purple color. In 1796 Cavanilles flowered a third plant from the parts sent by Cervantes, which he named Dahlia coccinea for its scarlet color.In 1798, Cavanilles sent D. Pinnata seeds to Parma, Italy. That year, the Marchioness of Bute, wife of The Earl of Bute, the English Ambassador to Spain, obtained a few seeds from Cavanilles and sent them to Kew Gardens, where they flowered but were lost after two to three years. In the following years Madrid sent seeds to Berlin and Dresden in Germany, and to Turin and Thiene in Italy. In 1802, Cavanilles sent tubers of "these three" (D. pinnata, D. rosea, D. coccinea) to Swiss botanist Augustin Pyramus de Candolle at University of Montpelier in France, Andre Thouin at the Jardin des Plantes in Paris and Scottish botanist William Aiton at Kew Gardens. That same year, John Fraser, English nurseryman and later botanical collector to the Czar of Russia, brought D. coccinea seeds from Paris to the Apothecaries Gardens in England, where they flowered in his greenhouse a year later, providing Botanical Magazine with an illustration.In 1804, a new species, Dahlia sambucifolia, was successfully grown at Holland House, Kensington. Whilst in Madrid in 1804, Lady Holland was given either dahlia seeds or tubers by Cavanilles. She sent them back to England, to Lord Holland's librarian Mr Buonaiuti at Holland House, who successfully raised the plants. A year later, Buonaiuti produced two double flowers. The plants raised in 1804 did not survive; new stock was brought from France in 1815. In 1824, Lord Holland sent his wife a note containing the following verse:
"The dahlia you brought to our isle
Your praises for ever shall speak;
Mid gardens as sweet as your smile,
And in colour as bright as your cheek."
In 1805, German naturalist Alexander von Humboldt sent more seeds from Mexico to Aiton in England, Thouin in Paris, and Christoph Friedrich Otto, director of the Berlin Botanical Garden. More significantly, he sent seeds to botanist Carl Ludwig Willdenow in Germany. Willdenow now reclassified the rapidly growing number of species, changing the genus from Dahlia to Georgina; after naturalist Johann Gottlieb Georgi. He combined the Cavanilles species D. pinnata and D. rosea under the name of Georgina variabilis; D. coccinea was still held to be a separate species, which he renamed Georgina coccinea.
CLASSIFICATION
Since 1789 when Cavanilles first flowered the dahlia in Europe, there has been an ongoing effort by many growers, botanists and taxonomists, to determine the development of the dahlia to modern times. At least 85 species have been reported: approximately 25 of these were first reported from the wild, the remainder appeared in gardens in Europe. They were considered hybrids, the results of crossing between previously reported species, or developed from the seeds sent by Humboldt from Mexico in 1805, or perhaps from some other undocumented seeds that had found their way to Europe. Several of these were soon discovered to be identical with earlier reported species, but the greatest number are new varieties. Morphological variation is highly pronounced in the dahlia. William John Cooper Lawrence, who hybridized hundreds of families of dahlias in the 1920s, stated: "I have not yet seen any two plants in the families I have raised which were not to be distinguished one from the other. Constant reclassification of the 85 reported species has resulted in a considerably smaller number of distinct species, as there is a great deal of disagreement today between systematists over classification.
In 1829, all species growing in Europe were reclassified under an all-encompassing name of D. variabilis, Desf., though this is not an accepted name. Through the interspecies cross of the Humboldt seeds and the Cavanilles species, 22 new species were reported by that year, all of which had been classified in different ways by several different taxonomists, creating considerable confusion as to which species was which.
In 1830 William Smith suggested that all dahlia species could be divided into two groups for color, red-tinged and purple-tinged. In investigating this idea Lawrence determined that with the exception of D. variabilis, all dahlia species may be assigned to one of two groups for flower-colour: Group I (ivory-magenta) or Group II (yellow-orange-scarlet).
CIRCUMSCRIPTION
The genus Dahlia is situated in the Asteroideae subfamily of the Asteraceae, in the Coreopsideae tribe. Within that tribe it is the second largest genus, after Coreopsis, and appears as a well defined clade within the Coreopsideae.
SUBDIVISION
INFRAGENERIC SUBDIVISION
Sherff (1955), in the first modern taxonomy described three sections for the 18 species he recognised, Pseudodendron, Epiphytum and Dahlia. By 1969 Sørensen recognised 29 species and four sections by splitting off Entemophyllon from section Dahlia. By contrast Giannasi (1975) using a phytochemical analysis based on flavonoids, reduced the genus to just two sections, Entemophyllon and Dahlia, the latter having three subsections, Pseudodendron, Dahlia, and Merckii. Sørensen then issued a further revision in 1980, incorporating subsection Merckii in his original section Dahlia. When he described two new species in the 1980s (Dahlia tubulata and D. congestifolia), he placed them within his existing sections. A further species, Dahlia sorensenii was added by Hansen and Hjerting in (1996). At the same time they demonstrated that Dahlia pinnata should more properly be designated D. x pinnata. D. x pinnata was shown to actually be a variant of D. sorensenii that had acquired hybrid qualities before it was introduced to Europe in the sixteenth century and formally named by Cavanilles. The original wild D. pinnata is presumed extinct. Further species continue to be described, Saar (2003) describing 35 species. However separation of the sections on morphological, cytologal and biocemical criteria has not been entirely satisfactory.
To date these sectional divisions have not been fully supported phylogenetically, which demonstrate only section Entemophyllon as a distinct sectional clade. The other major grouping is the Core Dahlia Clade (CDC), which includes most of section Dahlia. The remainder of the species occupy what has been described as the Variable Root Clade (VRC) which includes the small section Pseudodendron but also the monotypic section Epiphytum and a number of species from within section Dahlia. Outside of these three clades lie D. tubulata and D. merckii as a polytomy.
Horticulturally the sections retain some usage, section Pseudodendron being referred to as 'Tree Dahlias', Epiphytum as the 'Vine Dahlia'. The remaining two herbaceous sections being distinguished by their pinnules, opposing (Dahlia) or alternating (Entemophyllon).
SECTIONS
Sections (including chromosome numbers), with geographical distribution;
- Epiphytum Sherff (2n = 32)
10 m tall climber with aerial roots 5 cm thick and up to more than 20 m long; pinnules opposite
1 species, D. macdougallii Sherff
Mexico: Oaxaca
- Entemophyllon P. D. Sorensen (2n = 34)
6 species
Mexico: Hidalgo, Nuevo León, Tamaulipas, Querétaro, Durango, San Luis Potosí
- Pseudodendron P. D. Sorensen (2n = 32)
3 species + D. excelsa of uncertain identity
Mexico: Chiapas, Guerrero, Jalisco, Michoacan, Oaxaca, and
Costa Rica, El Salvador, Guatemala & Colombia
- Dahlia (2n = 32, 36 or 64)
24 species
Mexico: Distrito Federal, Guerrero, Hidalgo, Morelos, Nuevo León, Puebla, San Luis Potosí, Tamaulipas, Veracruz, Oaxaca, Puebla, Chiapas, México, Huehuetenango, Chihuahua, Durango, Michoacan & Guatemala
Only Pseudodendron (D. imperialis) and Dahlia (D. australis, D. coccinea) occur outside Mexico.
SPECIES
There are currently 42 accepted species in the Dahlia genus, but new species continue to be described.
ETYMOLOGY
The naming of the plant itself has long been a subject of some confusion. Many sources state that the name "Dahlia" was bestowed by the pioneering Swedish botanist and taxonomist Carl Linnaeus to honor his late student, Anders Dahl, author of Observationes Botanicae. However, Linnaeus died in 1778, more than eleven years before the plant was introduced into Europe in 1789, so while it is generally agreed that the plant was named in 1791 in honor of Dahl, who had died two years before, Linnaeus could not have been the one who did so. It was probably Abbe Antonio Jose Cavanilles, Director of the Royal Gardens of Madrid, who should be credited with the attempt to scientifically define the genus, since he not only received the first specimens from Mexico in 1789, but named the first three species that flowered from the cuttings.
Regardless of who bestowed it, the name was not so easily established. In 1805, German botanist Carl Ludwig Willdenow, asserting that the genus Dahlia Thunb. (published a year after Cavanilles's genus and now considered a synonym of Trichocladus) was more widely accepted, changed the plants' genus from Dahlia to Georgina; after the German-born naturalist Johann Gottlieb Georgi, a professor at the Imperial Academy of Sciences of St. Petersburg, Russia. He also reclassified and renamed the first three species grown, and identified, by Cavanilles. It was not until 1810, in a published article, that he officially adopted the Cavanilles' original designation of Dahlia. However, the name Georgina still persisted in Germany for the next few decades.
"Dahl" is a homophone of the Swedish word "dal", or "valley"; although it is not a true translation, the plant is sometimes referred to as the "valley flower".
DISTRIBUTION AND HABITAT
Predominantly Mexico, but some species are found ranging as far south as northern South America. D. australis occurs at least as far south as southwestern Guatemala, while D. coccinea and D. imperialis also occur in parts of Central America and northern South America. Dahlia is a genus of the uplands and mountains, being found at elevations between 1,500 and 3,700 meters, in what has been described as a "pine-oak woodland" vegetative zone. Most species have limited ranges scattered throughout many mountain ranges in Mexico.
ECOLOGY
The commonest pollinators are bees and small beetles.
PESTS AND DISEASES
Slugs and snails are serious pests in some parts of the world, particularly in spring when new growth is emerging through the soil. Earwigs can also disfigure the blooms. The other main pests likely to be encountered are aphids (usually on young stems and immature flower buds), red spider mite (causing foliage mottling and discolouration, worse in hot and dry conditions) and capsid bugs (resulting in contortion and holes at growing tips). Diseases affecting dahlias include powdery mildew, grey mould (Botrytis cinerea), verticillium wilt, dahlia smut (Entyloma calendulae f. dahliae), phytophthora and some plant viruses. Dahlias are a source of food for the larvae of some Lepidoptera species including Angle Shades, Common Swift, Ghost Moth and Large Yellow Underwing.
CULTIVATION
Dahlias grow naturally in climates which do not experience frost (the tubers are hardy to USDA Zone 8), consequently they are not adapted to withstand sub-zero temperatures. However, their tuberous nature enables them to survive periods of dormancy, and this characteristic means that gardeners in temperate climates with frosts can grow dahlias successfully, provided the tubers are lifted from the ground and stored in cool yet frost-free conditions during the winter. Planting the tubers quite deep (10 – 15 cm) also provides some protection. When in active growth, modern dahlia hybrids perform most successfully in well-watered yet free-draining soils, in situations receiving plenty of sunlight. Taller cultivars usually require some form of staking as they grow, and all garden dahlias need deadheading regularly, once flowering commences.
HORTICURAL CLASSIFICATION
HISTORY
The inappropriate term D. variabilis is often used to describe the cultivars of Dahlia since the correct parentage remains obscure, but probably involves Dahlia coccinea. In 1846 the Caledonia Horticultural Society of Edinburgh offered a prize of 2,000 pounds to the first person succeeding in producing a blue dahlia. This has to date not been accomplished. While dahlias produce anthocyanin, an element necessary for the production of the blue, to achieve a true blue color in a plant, the anthocyanin delphinidin needs six hydroxyl groups. To date dahlias have only developed five, so the closest that breeders have come to achieving a "blue" specimen are variations of mauve, purples and lilac hues.
By the beginning of the twentieth century a number of different types were recognised. These terms were based on shape or colour, and the National Dahlia Society included cactus, pompon, single, show and fancy in its 1904 guide. Many national societies developed their own classification systems until 1962 when the International Horticultural Congress agreed to develop an internationally recognised system at it Brussels meeting that year, and subsequently in Maryland in 1966. This culminated in the 1969 publication of The International Register of Dahlia Names by the Royal Horticultural Society which became the central registering authority.
This system depended primarily on the visibility of the central disc, whether it was open centred or whether only ray florets were apparent centrally (double bloom). The double bloom cultivars were then subdivided according to the way in which they were folded along their longitudinal axis, flat, involute (curled inwards) or revolute (curling backwards). If the end of the ray floret was split, they were considered fimbriated. Based on these characteristics, nine groups were defined plua a tenth miscellaneous group for any cultivars not fitting the above characteristics. Fimbriated dahlias were added in 2004, and two further groups (Single and Double orchid) in 2007. The last group to be added, Peony, first appeared in 2012.
In many cases the bloom diametre was then used to further label certain groups from miniature through to giant. This practice was abandoned in 2012.
MODERN SYSTEM (RHS)
There are now more than 57,000 registered cultivars, which are officially registered through the Royal Horticultural Society (RHS). The official register is The International Register of Dahlia Names 1969 (1995 reprint) which is updated by annual supplements. The original 1969 registry published about 14,000 cultivars adding a further 1700 by 1986 and in 2003 there were 18,000. Since then about a hundred new cultivars are added annually.
FLOWER TYPE
The official RHS classification lists fourteen groups, grouped by flower type, together with the abbreviations used by the RHS;
Group 1 – Single-flowered dahlias (Sin) — Flower has a central disc with a single outer ring of florets (which may overlap) encircling it, and which may be rounded or pointed.
Group 2 – Anemone-flowered dahlias (Anem) — The centre of the flower consists of dense elongated tubular florets, longer than the disc florets of Single dahlias, while the outer parts have one or more rings of flatter ray florets. Disc absent.
Group 3 – Collerette dahlias (Col) — Large flat florets forming a single outer ring around a central disc and which may overlap a smaller circle of florets closer to the centre, which have the appearance of a collar.
Group 4 – Waterlily dahlias (WL) — Double blooms, broad sparse curved, slightly curved or flat florets and very shallow in depth compared with other dahlias. Depth less than half the diameter of the bloom. Group 5 – Decorative dahlias (D) — Double blooms, ray florets broad, flat, involute no more than seventy five per cent of the longitudinal axis, slightly twisted and usually bluntly pointed. No visible central disc.
Group 6 – Ball dahlias (Ba)— Double blooms that are ball shaped or slightly flattened. Ray florets blunt or rounded at the tips, margins arranged spirally, involute for at least seventy five percent of the length of the florets. Larger than Pompons.
Group 7 – Pompon dahlias (Pom) — Double spherical miniature flowers made up entirely from florets that are curved inwards (involute) for their entire length (longitudinal axis), resembling a pompon.
Group 8 – Cactus dahlias (C) — Double blooms, ray florets pointed, with majority revolute (rolled) over more than fifty percent of their longitudinal axis, and straight or incurved. Narrower than Semi cactus.
Group 9 – Semi cactus dahlias (S–c)— Double blooms, very pointed ray florets, revolute for greater than twenty five percent and less than fifty percent of their longitudinal axis. Broad at the base and straight or incurved, almost spiky in appearance.
Group 10 – Miscellaneous dahlias (Misc) — not described in any other group.
Group 11 – Fimbriated dahlias (Fim) — ray florets evenly split or notched into two or more divisions, uniformly throughout the bloom, creating a fimbriated (fringed) effect. The petals may be flat, involute, revolute, straight, incurving or twisted.
Group 12 – Single Orchid (Star) dahlias (SinO) — single outer ring of florets surround a central disc. The ray florets are either involute or revolute.
Group 13 – Double Orchid dahlias (DblO) — Double blooms with triangular centres. The ray florets are narrowly lanceolate and are either involute or revolute. The central disc is absent.
Group 14 – Peony-flowered dahlias (P) — Large flowers with three or four rows of rays that are flattened and expanded and arranged irregularly. The rays surround a golden disc similar to that of Single dahlias.
FLOWER SIZE
Earlier versions of the registry subdivided some groups by flower size. Groups 4, 5, 8 and 9 were divided into five subgroups (A to E) from Giant to Miniature, and Group 6 into two subgroups, Small and Miniature. Dahlias were then described by Group and Subgroup, e.g. 5(d) ‘Ace Summer Sunset’. Some Dahlia Societies have continued this practice, but this is neither official nor standardised. As of 2013 The RHS uses two size descriptors
Dwarf Bedder (Dw.B.) — not usually exceeding 600 mm in height, e.g. 'Preston Park' (Sin/DwB)
Lilliput dahlias (Lil) — not usually exceeding 300 mm in height, with single, semi-double or double florets up to 26 mm in diameter. ("baby" or "top-mix" dahlias), e.g. 'Harvest Tiny Tot' (Misc/Lil)
Sizes can range from tiny micro dahlias with flowers less than 50mm to giants that are over 250mm in diameter. The groupings listed here are from the New Zealand Society.
Giant flowered cultivars have blooms with a diameter of over 250mm.
Large flowered cultivars have blooms with a diameter between 200mm-250mm.
Medium flowered cultivars have blooms with a diameter between 155mm-200mm.
Small flowered cultivars have blooms with a diameter between 115mm-155mm.
Miniature flowered cultivars have blooms with a diameter between 50mm-115mm.
Pompom flowered cultivars have blooms with a diameter less than 50mm.
In addition to the official classification and the terminology used by various dahlia societies, individual horticulturalists use a wide range of other descriptions, such as 'Incurved' and abbreviations in their catalogues, such as CO for Collarette.
BRANDING
Some plant growers include their brand name in the cultivar name. Thus Fides (part of the Dümmen Orange Group) in the Netherlands developed a series of cultivars which they named the Dahlinova Series, for example Dahlinova 'Carolina Burgundy'. These are Group 10 Miscellaneous in the RHS classification scheme.
DOUBLE DAHLIAS
In 1805, several new species were reported with red, purple, lilac, and pale yellow coloring, and the first true double flower was produced in Belgium. One of the more popular concepts of dahlia history, and the basis for many different interpretations and confusion, is that all the original discoveries were single flowered types, which, through hybridization and selective breeding, produced double forms. Many of the species of dahlias then, and now, have single flowered blooms. coccinea, the third dahlia to bloom in Europe, was a single. But two of the three drawings of dahlias by Dominguez, made in Mexico between 1570–77, showed definite characteristics of doubling. In the early days of the dahlia in Europe, the word "double" simply designated flowers with more than one row of petals. The greatest effort was now directed to developing improved types of double dahlias.
During the years 1805 to 1810 several people claimed to have produced a double dahlia. In 1805 Henry C. Andrews made a drawing of such a plant in the collection of Lady Holland, grown from seedlings sent that year from Madrid. Like other doubles of the time it did not resemble the doubles of today. The first modern double, or full double, appeared in Belgium; M. Donckelaar, Director of the Botanic Garden at Louvain, selected plants for that characteristic, and within a few years secured three fully double forms. By 1826 double varieties were being grown almost exclusively, and there was very little interest in the single forms. Up to this time all the so-called double dahlias had been purple, or tinged with purple, and it was doubted if a variety untinged with that color was obtainable.
In 1843, scented single forms of dahlias were first reported in Neu Verbass, Austria. D. crocea, a fragrant variety grown from one of the Humboldt seeds, was probably interbred with the single D. coccinea. A new scented species would not be introduced until the next century when the D. coronata was brought from Mexico to Germany in 1907.
The exact date the dahlia was introduced in the United States is uncertain. One of the first Dahlias in the USA may be the D. coccinea speciosissima grown by Mr William Leathe, of Cambridgeport, near Boston, around 1929. According to Edward Sayers "it attracted much admiration, and at that time was considered a very elegant flower, it was however soon eclipsed by that splendid scarlet, the Countess of Liverpool". However 9 cultivars were already listed in the catalog from Thornburn, 1825. And even earlier reference can be found in a catalogue from the Linnaean Botanical Garden, New York, 1820, that includes one scarlet, one purple, and two double orange Dahlias for sale.
Sayers stated that "No person has done more for the introduction and advancement of the culture of the Dahlia than George C. Thorburn, of New York, who yearly flowers many thousand plants at his place at Hallet's Cove, near Harlaem. The show there in the flowering season is a rich treat for the lovers of floriculture : for almost every variety can be seen growing in two large blocks or masses which lead from the road to the dwelling-house, and form a complete field of the Dahlia as a foreground to the house. Mr T. Hogg, Mr William Read, and many other well known florists, have also contributed much in the vicinity of New York, to the introduction of the Dahlia. Indeed so general has become the taste that almost every garden has its show of the Dahlia in the season." In Boston too there were many collections, a collection from the Messrs Hovey of Cambridgeport was also mentioned.
In 1835 Thomas Bridgeman, published a list of 160 double dahlias in his Florist's Guide. 60 of the choicest were supplied by Mr. G. C. Thornburn of Astoria, N.Y. who got most of them from contacts in the UK. Not a few of them had taken prices "at the English and American exhibitions".
"STARS OF DEVIL"
In 1872 J.T. van der Berg of Utrecht in the Netherlands, received a shipment of seeds and plants from a friend in Mexico. The entire shipment was badly rotted and appeared to be ruined, but van der Berg examined it carefully and found a small piece of root that seemed alive. He planted and carefully tended it; it grew into a plant that he identified as a dahlia. He made cuttings from the plant during the winter of 1872-1873. This was an entirely different type of flower, with a rich, red color and a high degree of doubling. In 1874 van der Berg catalogued it for sale, calling it Dahlia juarezii to honor Mexican President Benito Pablo Juarez, who had died the year before, and described it as "...equal to the beautiful color of the red poppy. Its form is very outstanding and different in every respect of all known dahlia flowers.".
This plant has perhaps had a greater influence on the popularity of the modern dahlia than any other. Called "Les Etoiles de Diable" (Stars of the Devil) in France and "Cactus dahlia" elsewhere, the edges of its petals rolled backwards, rather than forward, and this new form revolutionized the dahlia world. It was thought to be a distinct mutation since no other plant that resembled it could be found in the wild. Today it is assumed that D. juarezii had, at one time, existed in Mexico and subsequently disappeared. Nurserymen in Europe crossbred this plant with dahlias discovered earlier; the results became the progenitors of all modern dahlia hybrids today.
AWARD OF GARDEN MERIT (RHS)
As of 2015, 124 dahlia cultivars have gained the Royal Horticultural Society's Award of Garden Merit:
"Bednall beauty"
"Bishop of Llandaff"
"Clair de lune"
"David Howard"
"Ellen Huston"
"Fascination"
"Gallery art deco"
"Gallery Art Nouveau"
"Glorie van Heemstede"
"Honka"
"Moonfire"
"Twyning's After Eight"
USES
FLORICULTURE
The asterid eudicots contain two economically important geophyte genera, Dahlia and Liatris. Horticulturally the garden dahlia is usually treated as the cultigen D. variabilis Hort., which while being responsible for thousands of cultivars has an obscure taxonomic status.
OTHER
Today the dahlia is still considered one of the native ingredients in Oaxacan cuisine; several cultivars are still grown especially for their large, sweet potato-like tubers. Dacopa, an intense mocha-tasting extract from the roasted tubers, is used to flavor beverages throughout Central America.
In Europe and America, prior to the discovery of insulin in 1923, diabetics - as well as consumptives - were often given a substance called Atlantic starch or diabetic sugar, derived from inulin, a naturally occurring form of fruit sugar, extracted from dahlia tubers. Inulin is still used in clinical tests for kidney functionality.
WIKIPEDIA
Dahlia (UK /deɪliə/ or US /dɑːliə/) is a genus of bushy, tuberous, herbaceous perennial plants native to Mexico. A member of the Asteraceae (or Compositae), dicotyledonous plants, related species include the sunflower, daisy, chrysanthemum, and zinnia. There are 42 species of dahlia, with hybrids commonly grown as garden plants. Flower forms are variable, with one head per stem; these can be as small as 5.1 cm diameter or up to 30 cm ("dinner plate"). This great variety results from dahlias being octoploids—that is, they have eight sets of homologous chromosomes, whereas most plants have only two. In addition, dahlias also contain many transposons - genetic pieces that move from place to place upon an allele - which contributes to their manifesting such great diversity.
The stems are leafy, ranging in height from as low as 30 cm to more than 1.8–2.4 m. The majority of species do not produce scented flowers or cultivars. Like most plants that do not attract pollinating insects through scent, they are brightly colored, displaying most hues, with the exception of blue.
The dahlia was declared the national flower of Mexico in 1963. The tubers were grown as a food crop by the Aztecs, but this use largely died out after the Spanish Conquest. Attempts to introduce the tubers as a food crop in Europe were unsuccessful.
DESCRIPTION
Perennial plants, with mostly tuberous roots. While some have herbaceous stems, others have stems which lignify in the absence of secondary tissue and resprout following winter dormancy, allowing further seasons of growth. as a member of the Asteraceae the flower head is actually a composite (hence the older name Compositae) with both central disc florets and surrounding ray florets. Each floret is a flower in its own right, but is often incorrectly described as a petal, particularly by horticulturalists. The modern mame Asteraceae refers to the appearance of a star with surrounding rays.
TAXONOMY
HISTORY
EARLY HISTORY
Spaniards reported finding the plants growing in Mexico in 1525, but the earliest known description is by Francisco Hernández, physician to Philip II, who was ordered to visit Mexico in 1570 to study the "natural products of that country". They were used as a source of food by the indigenous peoples, and were both gathered in the wild and cultivated. The Aztecs used them to treat epilepsy, and employed the long hollow stem of the (Dahlia imperalis) for water pipes. The indigenous peoples variously identified the plants as "Chichipatl" (Toltecs) and "Acocotle" or "Cocoxochitl" (Aztecs). From Hernandez' perception of Aztec, to Spanish, through various other translations, the word is "water cane", "water pipe", "water pipe flower", "hollow stem flower" and "cane flower". All these refer to the hollowness of the plants' stem.Hernandez described two varieties of dahlias (the pinwheel-like Dahlia pinnata and the huge Dahlia imperialis) as well as other medicinal plants of New Spain. Francisco Dominguez, a Hidalgo gentleman who accompanied Hernandez on part of his seven-year study, made a series of drawings to supplement the four volume report. Three of his drawings showed plants with flowers: two resembled the modern bedding dahlia, and one resembled the species Dahlia merki; all displayed a high degree of doubleness. In 1578 the manuscript, entitled Nova Plantarum, Animalium et Mineralium Mexicanorum Historia, was sent back to the Escorial in Madrid; they were not translated into Latin by Francisco Ximenes until 1615. In 1640, Francisco Cesi, President of the Academia Linei of Rome, bought the Ximenes translation, and after annotating it, published it in 1649-1651 in two volumes as Rerum Medicarum Novae Hispaniae Thesaurus Seu Nova Plantarium, Animalium et Mineraliuím Mexicanorum Historia. The original manuscripts were destroyed in a fire in the mid-1600s.
EUROPEAN INTRODUCTION
In 1787, the French botanist Nicolas-Joseph Thiéry de Menonville, sent to Mexico to steal the cochineal insect valued for its scarlet dye, reported the strangely beautiful flowers he had seen growing in a garden in Oaxaca. In 1789, Vicente Cervantes, Director of the Botanical Garden at Mexico City, sent "plant parts" to Abbe Antonio José Cavanilles, Director of the Royal Gardens of Madrid. Cavanilles flowered one plant that same year, then the second one a year later. In 1791 he called the new growths "Dahlia" for Anders Dahl. The first plant was called Dahlia pinnata after its pinnate foliage; the second, Dahlia rosea for its rose-purple color. In 1796 Cavanilles flowered a third plant from the parts sent by Cervantes, which he named Dahlia coccinea for its scarlet color.In 1798, Cavanilles sent D. Pinnata seeds to Parma, Italy. That year, the Marchioness of Bute, wife of The Earl of Bute, the English Ambassador to Spain, obtained a few seeds from Cavanilles and sent them to Kew Gardens, where they flowered but were lost after two to three years. In the following years Madrid sent seeds to Berlin and Dresden in Germany, and to Turin and Thiene in Italy. In 1802, Cavanilles sent tubers of "these three" (D. pinnata, D. rosea, D. coccinea) to Swiss botanist Augustin Pyramus de Candolle at University of Montpelier in France, Andre Thouin at the Jardin des Plantes in Paris and Scottish botanist William Aiton at Kew Gardens. That same year, John Fraser, English nurseryman and later botanical collector to the Czar of Russia, brought D. coccinea seeds from Paris to the Apothecaries Gardens in England, where they flowered in his greenhouse a year later, providing Botanical Magazine with an illustration.In 1804, a new species, Dahlia sambucifolia, was successfully grown at Holland House, Kensington. Whilst in Madrid in 1804, Lady Holland was given either dahlia seeds or tubers by Cavanilles. She sent them back to England, to Lord Holland's librarian Mr Buonaiuti at Holland House, who successfully raised the plants. A year later, Buonaiuti produced two double flowers. The plants raised in 1804 did not survive; new stock was brought from France in 1815. In 1824, Lord Holland sent his wife a note containing the following verse:
"The dahlia you brought to our isle
Your praises for ever shall speak;
Mid gardens as sweet as your smile,
And in colour as bright as your cheek."
In 1805, German naturalist Alexander von Humboldt sent more seeds from Mexico to Aiton in England, Thouin in Paris, and Christoph Friedrich Otto, director of the Berlin Botanical Garden. More significantly, he sent seeds to botanist Carl Ludwig Willdenow in Germany. Willdenow now reclassified the rapidly growing number of species, changing the genus from Dahlia to Georgina; after naturalist Johann Gottlieb Georgi. He combined the Cavanilles species D. pinnata and D. rosea under the name of Georgina variabilis; D. coccinea was still held to be a separate species, which he renamed Georgina coccinea.
CLASSIFICATION
Since 1789 when Cavanilles first flowered the dahlia in Europe, there has been an ongoing effort by many growers, botanists and taxonomists, to determine the development of the dahlia to modern times. At least 85 species have been reported: approximately 25 of these were first reported from the wild, the remainder appeared in gardens in Europe. They were considered hybrids, the results of crossing between previously reported species, or developed from the seeds sent by Humboldt from Mexico in 1805, or perhaps from some other undocumented seeds that had found their way to Europe. Several of these were soon discovered to be identical with earlier reported species, but the greatest number are new varieties. Morphological variation is highly pronounced in the dahlia. William John Cooper Lawrence, who hybridized hundreds of families of dahlias in the 1920s, stated: "I have not yet seen any two plants in the families I have raised which were not to be distinguished one from the other. Constant reclassification of the 85 reported species has resulted in a considerably smaller number of distinct species, as there is a great deal of disagreement today between systematists over classification.
In 1829, all species growing in Europe were reclassified under an all-encompassing name of D. variabilis, Desf., though this is not an accepted name. Through the interspecies cross of the Humboldt seeds and the Cavanilles species, 22 new species were reported by that year, all of which had been classified in different ways by several different taxonomists, creating considerable confusion as to which species was which.
In 1830 William Smith suggested that all dahlia species could be divided into two groups for color, red-tinged and purple-tinged. In investigating this idea Lawrence determined that with the exception of D. variabilis, all dahlia species may be assigned to one of two groups for flower-colour: Group I (ivory-magenta) or Group II (yellow-orange-scarlet).
CIRCUMSCRIPTION
The genus Dahlia is situated in the Asteroideae subfamily of the Asteraceae, in the Coreopsideae tribe. Within that tribe it is the second largest genus, after Coreopsis, and appears as a well defined clade within the Coreopsideae.
SUBDIVISION
INFRAGENERIC SUBDIVISION
Sherff (1955), in the first modern taxonomy described three sections for the 18 species he recognised, Pseudodendron, Epiphytum and Dahlia. By 1969 Sørensen recognised 29 species and four sections by splitting off Entemophyllon from section Dahlia. By contrast Giannasi (1975) using a phytochemical analysis based on flavonoids, reduced the genus to just two sections, Entemophyllon and Dahlia, the latter having three subsections, Pseudodendron, Dahlia, and Merckii. Sørensen then issued a further revision in 1980, incorporating subsection Merckii in his original section Dahlia. When he described two new species in the 1980s (Dahlia tubulata and D. congestifolia), he placed them within his existing sections. A further species, Dahlia sorensenii was added by Hansen and Hjerting in (1996). At the same time they demonstrated that Dahlia pinnata should more properly be designated D. x pinnata. D. x pinnata was shown to actually be a variant of D. sorensenii that had acquired hybrid qualities before it was introduced to Europe in the sixteenth century and formally named by Cavanilles. The original wild D. pinnata is presumed extinct. Further species continue to be described, Saar (2003) describing 35 species. However separation of the sections on morphological, cytologal and biocemical criteria has not been entirely satisfactory.
To date these sectional divisions have not been fully supported phylogenetically, which demonstrate only section Entemophyllon as a distinct sectional clade. The other major grouping is the Core Dahlia Clade (CDC), which includes most of section Dahlia. The remainder of the species occupy what has been described as the Variable Root Clade (VRC) which includes the small section Pseudodendron but also the monotypic section Epiphytum and a number of species from within section Dahlia. Outside of these three clades lie D. tubulata and D. merckii as a polytomy.
Horticulturally the sections retain some usage, section Pseudodendron being referred to as 'Tree Dahlias', Epiphytum as the 'Vine Dahlia'. The remaining two herbaceous sections being distinguished by their pinnules, opposing (Dahlia) or alternating (Entemophyllon).
SECTIONS
Sections (including chromosome numbers), with geographical distribution;
- Epiphytum Sherff (2n = 32)
10 m tall climber with aerial roots 5 cm thick and up to more than 20 m long; pinnules opposite
1 species, D. macdougallii Sherff
Mexico: Oaxaca
- Entemophyllon P. D. Sorensen (2n = 34)
6 species
Mexico: Hidalgo, Nuevo León, Tamaulipas, Querétaro, Durango, San Luis Potosí
- Pseudodendron P. D. Sorensen (2n = 32)
3 species + D. excelsa of uncertain identity
Mexico: Chiapas, Guerrero, Jalisco, Michoacan, Oaxaca, and
Costa Rica, El Salvador, Guatemala & Colombia
- Dahlia (2n = 32, 36 or 64)
24 species
Mexico: Distrito Federal, Guerrero, Hidalgo, Morelos, Nuevo León, Puebla, San Luis Potosí, Tamaulipas, Veracruz, Oaxaca, Puebla, Chiapas, México, Huehuetenango, Chihuahua, Durango, Michoacan & Guatemala
Only Pseudodendron (D. imperialis) and Dahlia (D. australis, D. coccinea) occur outside Mexico.
SPECIES
There are currently 42 accepted species in the Dahlia genus, but new species continue to be described.
ETYMOLOGY
The naming of the plant itself has long been a subject of some confusion. Many sources state that the name "Dahlia" was bestowed by the pioneering Swedish botanist and taxonomist Carl Linnaeus to honor his late student, Anders Dahl, author of Observationes Botanicae. However, Linnaeus died in 1778, more than eleven years before the plant was introduced into Europe in 1789, so while it is generally agreed that the plant was named in 1791 in honor of Dahl, who had died two years before, Linnaeus could not have been the one who did so. It was probably Abbe Antonio Jose Cavanilles, Director of the Royal Gardens of Madrid, who should be credited with the attempt to scientifically define the genus, since he not only received the first specimens from Mexico in 1789, but named the first three species that flowered from the cuttings.
Regardless of who bestowed it, the name was not so easily established. In 1805, German botanist Carl Ludwig Willdenow, asserting that the genus Dahlia Thunb. (published a year after Cavanilles's genus and now considered a synonym of Trichocladus) was more widely accepted, changed the plants' genus from Dahlia to Georgina; after the German-born naturalist Johann Gottlieb Georgi, a professor at the Imperial Academy of Sciences of St. Petersburg, Russia. He also reclassified and renamed the first three species grown, and identified, by Cavanilles. It was not until 1810, in a published article, that he officially adopted the Cavanilles' original designation of Dahlia. However, the name Georgina still persisted in Germany for the next few decades.
"Dahl" is a homophone of the Swedish word "dal", or "valley"; although it is not a true translation, the plant is sometimes referred to as the "valley flower".
DISTRIBUTION AND HABITAT
Predominantly Mexico, but some species are found ranging as far south as northern South America. D. australis occurs at least as far south as southwestern Guatemala, while D. coccinea and D. imperialis also occur in parts of Central America and northern South America. Dahlia is a genus of the uplands and mountains, being found at elevations between 1,500 and 3,700 meters, in what has been described as a "pine-oak woodland" vegetative zone. Most species have limited ranges scattered throughout many mountain ranges in Mexico.
ECOLOGY
The commonest pollinators are bees and small beetles.
PESTS AND DISEASES
Slugs and snails are serious pests in some parts of the world, particularly in spring when new growth is emerging through the soil. Earwigs can also disfigure the blooms. The other main pests likely to be encountered are aphids (usually on young stems and immature flower buds), red spider mite (causing foliage mottling and discolouration, worse in hot and dry conditions) and capsid bugs (resulting in contortion and holes at growing tips). Diseases affecting dahlias include powdery mildew, grey mould (Botrytis cinerea), verticillium wilt, dahlia smut (Entyloma calendulae f. dahliae), phytophthora and some plant viruses. Dahlias are a source of food for the larvae of some Lepidoptera species including Angle Shades, Common Swift, Ghost Moth and Large Yellow Underwing.
CULTIVATION
Dahlias grow naturally in climates which do not experience frost (the tubers are hardy to USDA Zone 8), consequently they are not adapted to withstand sub-zero temperatures. However, their tuberous nature enables them to survive periods of dormancy, and this characteristic means that gardeners in temperate climates with frosts can grow dahlias successfully, provided the tubers are lifted from the ground and stored in cool yet frost-free conditions during the winter. Planting the tubers quite deep (10 – 15 cm) also provides some protection. When in active growth, modern dahlia hybrids perform most successfully in well-watered yet free-draining soils, in situations receiving plenty of sunlight. Taller cultivars usually require some form of staking as they grow, and all garden dahlias need deadheading regularly, once flowering commences.
HORTICURAL CLASSIFICATION
HISTORY
The inappropriate term D. variabilis is often used to describe the cultivars of Dahlia since the correct parentage remains obscure, but probably involves Dahlia coccinea. In 1846 the Caledonia Horticultural Society of Edinburgh offered a prize of 2,000 pounds to the first person succeeding in producing a blue dahlia. This has to date not been accomplished. While dahlias produce anthocyanin, an element necessary for the production of the blue, to achieve a true blue color in a plant, the anthocyanin delphinidin needs six hydroxyl groups. To date dahlias have only developed five, so the closest that breeders have come to achieving a "blue" specimen are variations of mauve, purples and lilac hues.
By the beginning of the twentieth century a number of different types were recognised. These terms were based on shape or colour, and the National Dahlia Society included cactus, pompon, single, show and fancy in its 1904 guide. Many national societies developed their own classification systems until 1962 when the International Horticultural Congress agreed to develop an internationally recognised system at it Brussels meeting that year, and subsequently in Maryland in 1966. This culminated in the 1969 publication of The International Register of Dahlia Names by the Royal Horticultural Society which became the central registering authority.
This system depended primarily on the visibility of the central disc, whether it was open centred or whether only ray florets were apparent centrally (double bloom). The double bloom cultivars were then subdivided according to the way in which they were folded along their longitudinal axis, flat, involute (curled inwards) or revolute (curling backwards). If the end of the ray floret was split, they were considered fimbriated. Based on these characteristics, nine groups were defined plua a tenth miscellaneous group for any cultivars not fitting the above characteristics. Fimbriated dahlias were added in 2004, and two further groups (Single and Double orchid) in 2007. The last group to be added, Peony, first appeared in 2012.
In many cases the bloom diametre was then used to further label certain groups from miniature through to giant. This practice was abandoned in 2012.
MODERN SYSTEM (RHS)
There are now more than 57,000 registered cultivars, which are officially registered through the Royal Horticultural Society (RHS). The official register is The International Register of Dahlia Names 1969 (1995 reprint) which is updated by annual supplements. The original 1969 registry published about 14,000 cultivars adding a further 1700 by 1986 and in 2003 there were 18,000. Since then about a hundred new cultivars are added annually.
FLOWER TYPE
The official RHS classification lists fourteen groups, grouped by flower type, together with the abbreviations used by the RHS;
Group 1 – Single-flowered dahlias (Sin) — Flower has a central disc with a single outer ring of florets (which may overlap) encircling it, and which may be rounded or pointed.
Group 2 – Anemone-flowered dahlias (Anem) — The centre of the flower consists of dense elongated tubular florets, longer than the disc florets of Single dahlias, while the outer parts have one or more rings of flatter ray florets. Disc absent.
Group 3 – Collerette dahlias (Col) — Large flat florets forming a single outer ring around a central disc and which may overlap a smaller circle of florets closer to the centre, which have the appearance of a collar.
Group 4 – Waterlily dahlias (WL) — Double blooms, broad sparse curved, slightly curved or flat florets and very shallow in depth compared with other dahlias. Depth less than half the diameter of the bloom. Group 5 – Decorative dahlias (D) — Double blooms, ray florets broad, flat, involute no more than seventy five per cent of the longitudinal axis, slightly twisted and usually bluntly pointed. No visible central disc.
Group 6 – Ball dahlias (Ba)— Double blooms that are ball shaped or slightly flattened. Ray florets blunt or rounded at the tips, margins arranged spirally, involute for at least seventy five percent of the length of the florets. Larger than Pompons.
Group 7 – Pompon dahlias (Pom) — Double spherical miniature flowers made up entirely from florets that are curved inwards (involute) for their entire length (longitudinal axis), resembling a pompon.
Group 8 – Cactus dahlias (C) — Double blooms, ray florets pointed, with majority revolute (rolled) over more than fifty percent of their longitudinal axis, and straight or incurved. Narrower than Semi cactus.
Group 9 – Semi cactus dahlias (S–c)— Double blooms, very pointed ray florets, revolute for greater than twenty five percent and less than fifty percent of their longitudinal axis. Broad at the base and straight or incurved, almost spiky in appearance.
Group 10 – Miscellaneous dahlias (Misc) — not described in any other group.
Group 11 – Fimbriated dahlias (Fim) — ray florets evenly split or notched into two or more divisions, uniformly throughout the bloom, creating a fimbriated (fringed) effect. The petals may be flat, involute, revolute, straight, incurving or twisted.
Group 12 – Single Orchid (Star) dahlias (SinO) — single outer ring of florets surround a central disc. The ray florets are either involute or revolute.
Group 13 – Double Orchid dahlias (DblO) — Double blooms with triangular centres. The ray florets are narrowly lanceolate and are either involute or revolute. The central disc is absent.
Group 14 – Peony-flowered dahlias (P) — Large flowers with three or four rows of rays that are flattened and expanded and arranged irregularly. The rays surround a golden disc similar to that of Single dahlias.
FLOWER SIZE
Earlier versions of the registry subdivided some groups by flower size. Groups 4, 5, 8 and 9 were divided into five subgroups (A to E) from Giant to Miniature, and Group 6 into two subgroups, Small and Miniature. Dahlias were then described by Group and Subgroup, e.g. 5(d) ‘Ace Summer Sunset’. Some Dahlia Societies have continued this practice, but this is neither official nor standardised. As of 2013 The RHS uses two size descriptors
Dwarf Bedder (Dw.B.) — not usually exceeding 600 mm in height, e.g. 'Preston Park' (Sin/DwB)
Lilliput dahlias (Lil) — not usually exceeding 300 mm in height, with single, semi-double or double florets up to 26 mm in diameter. ("baby" or "top-mix" dahlias), e.g. 'Harvest Tiny Tot' (Misc/Lil)
Sizes can range from tiny micro dahlias with flowers less than 50mm to giants that are over 250mm in diameter. The groupings listed here are from the New Zealand Society.
Giant flowered cultivars have blooms with a diameter of over 250mm.
Large flowered cultivars have blooms with a diameter between 200mm-250mm.
Medium flowered cultivars have blooms with a diameter between 155mm-200mm.
Small flowered cultivars have blooms with a diameter between 115mm-155mm.
Miniature flowered cultivars have blooms with a diameter between 50mm-115mm.
Pompom flowered cultivars have blooms with a diameter less than 50mm.
In addition to the official classification and the terminology used by various dahlia societies, individual horticulturalists use a wide range of other descriptions, such as 'Incurved' and abbreviations in their catalogues, such as CO for Collarette.
BRANDING
Some plant growers include their brand name in the cultivar name. Thus Fides (part of the Dümmen Orange Group) in the Netherlands developed a series of cultivars which they named the Dahlinova Series, for example Dahlinova 'Carolina Burgundy'. These are Group 10 Miscellaneous in the RHS classification scheme.
DOUBLE DAHLIAS
In 1805, several new species were reported with red, purple, lilac, and pale yellow coloring, and the first true double flower was produced in Belgium. One of the more popular concepts of dahlia history, and the basis for many different interpretations and confusion, is that all the original discoveries were single flowered types, which, through hybridization and selective breeding, produced double forms. Many of the species of dahlias then, and now, have single flowered blooms. coccinea, the third dahlia to bloom in Europe, was a single. But two of the three drawings of dahlias by Dominguez, made in Mexico between 1570–77, showed definite characteristics of doubling. In the early days of the dahlia in Europe, the word "double" simply designated flowers with more than one row of petals. The greatest effort was now directed to developing improved types of double dahlias.
During the years 1805 to 1810 several people claimed to have produced a double dahlia. In 1805 Henry C. Andrews made a drawing of such a plant in the collection of Lady Holland, grown from seedlings sent that year from Madrid. Like other doubles of the time it did not resemble the doubles of today. The first modern double, or full double, appeared in Belgium; M. Donckelaar, Director of the Botanic Garden at Louvain, selected plants for that characteristic, and within a few years secured three fully double forms. By 1826 double varieties were being grown almost exclusively, and there was very little interest in the single forms. Up to this time all the so-called double dahlias had been purple, or tinged with purple, and it was doubted if a variety untinged with that color was obtainable.
In 1843, scented single forms of dahlias were first reported in Neu Verbass, Austria. D. crocea, a fragrant variety grown from one of the Humboldt seeds, was probably interbred with the single D. coccinea. A new scented species would not be introduced until the next century when the D. coronata was brought from Mexico to Germany in 1907.
The exact date the dahlia was introduced in the United States is uncertain. One of the first Dahlias in the USA may be the D. coccinea speciosissima grown by Mr William Leathe, of Cambridgeport, near Boston, around 1929. According to Edward Sayers "it attracted much admiration, and at that time was considered a very elegant flower, it was however soon eclipsed by that splendid scarlet, the Countess of Liverpool". However 9 cultivars were already listed in the catalog from Thornburn, 1825. And even earlier reference can be found in a catalogue from the Linnaean Botanical Garden, New York, 1820, that includes one scarlet, one purple, and two double orange Dahlias for sale.
Sayers stated that "No person has done more for the introduction and advancement of the culture of the Dahlia than George C. Thorburn, of New York, who yearly flowers many thousand plants at his place at Hallet's Cove, near Harlaem. The show there in the flowering season is a rich treat for the lovers of floriculture : for almost every variety can be seen growing in two large blocks or masses which lead from the road to the dwelling-house, and form a complete field of the Dahlia as a foreground to the house. Mr T. Hogg, Mr William Read, and many other well known florists, have also contributed much in the vicinity of New York, to the introduction of the Dahlia. Indeed so general has become the taste that almost every garden has its show of the Dahlia in the season." In Boston too there were many collections, a collection from the Messrs Hovey of Cambridgeport was also mentioned.
In 1835 Thomas Bridgeman, published a list of 160 double dahlias in his Florist's Guide. 60 of the choicest were supplied by Mr. G. C. Thornburn of Astoria, N.Y. who got most of them from contacts in the UK. Not a few of them had taken prices "at the English and American exhibitions".
"STARS OF DEVIL"
In 1872 J.T. van der Berg of Utrecht in the Netherlands, received a shipment of seeds and plants from a friend in Mexico. The entire shipment was badly rotted and appeared to be ruined, but van der Berg examined it carefully and found a small piece of root that seemed alive. He planted and carefully tended it; it grew into a plant that he identified as a dahlia. He made cuttings from the plant during the winter of 1872-1873. This was an entirely different type of flower, with a rich, red color and a high degree of doubling. In 1874 van der Berg catalogued it for sale, calling it Dahlia juarezii to honor Mexican President Benito Pablo Juarez, who had died the year before, and described it as "...equal to the beautiful color of the red poppy. Its form is very outstanding and different in every respect of all known dahlia flowers.".
This plant has perhaps had a greater influence on the popularity of the modern dahlia than any other. Called "Les Etoiles de Diable" (Stars of the Devil) in France and "Cactus dahlia" elsewhere, the edges of its petals rolled backwards, rather than forward, and this new form revolutionized the dahlia world. It was thought to be a distinct mutation since no other plant that resembled it could be found in the wild. Today it is assumed that D. juarezii had, at one time, existed in Mexico and subsequently disappeared. Nurserymen in Europe crossbred this plant with dahlias discovered earlier; the results became the progenitors of all modern dahlia hybrids today.
AWARD OF GARDEN MERIT (RHS)
As of 2015, 124 dahlia cultivars have gained the Royal Horticultural Society's Award of Garden Merit:
"Bednall beauty"
"Bishop of Llandaff"
"Clair de lune"
"David Howard"
"Ellen Huston"
"Fascination"
"Gallery art deco"
"Gallery Art Nouveau"
"Glorie van Heemstede"
"Honka"
"Moonfire"
"Twyning's After Eight"
USES
FLORICULTURE
The asterid eudicots contain two economically important geophyte genera, Dahlia and Liatris. Horticulturally the garden dahlia is usually treated as the cultigen D. variabilis Hort., which while being responsible for thousands of cultivars has an obscure taxonomic status.
OTHER
Today the dahlia is still considered one of the native ingredients in Oaxacan cuisine; several cultivars are still grown especially for their large, sweet potato-like tubers. Dacopa, an intense mocha-tasting extract from the roasted tubers, is used to flavor beverages throughout Central America.
In Europe and America, prior to the discovery of insulin in 1923, diabetics - as well as consumptives - were often given a substance called Atlantic starch or diabetic sugar, derived from inulin, a naturally occurring form of fruit sugar, extracted from dahlia tubers. Inulin is still used in clinical tests for kidney functionality.
WIKIPEDIA
Bituminaria bituminosa (L.) C. H. Stirt., syn.: Psoralea bituminosa L., Aspalthium bituminosum (L.) Fourr., Psoralea palaestina Gouan, Asphalthium bituminosum (L.) Medik.
Family: Fabaceae
EN: Arabian Pea, Pitch Trefoil, DE: Gewöhnlicher Asphaltklee
Slo.: arabski grah
Dat.: May 21. 2007
Lat.: 45,00508 Long.: 13,81403 WGS84
Code: Bot_0189/2007_DSC8001 and DSC8037, Bot_0190/2007_DSC8116, Bot_0191/2007_DSC8228
Habitat: Dry grassland with some bushes, flat terrain, open, sunny location; elevation 125 m (410 feet); average precipitations ~ 1.000 mm/year, average temperature 13-15 deg C, Sub-Mediterranean phytogeographical region.
Substratum: soil.
Place: Croatia, Istria peninsula, approximately 4.3 km south-southeast of Bale, east of the Bale-Pula road at the intersection of the local road leading to the village of Gajana.
Comment regarding the Flick album Bituminaria bituminosa: Bituminaria bituminosa is an intriguing and relatively uncommon Mediterranean plant. It is prevalent along the coasts of the Mediterranean Sea in all countries except Syria and Egypt. To the east, it extends as far as the Caucasus and the shores of the Black Sea (Ref.: 4).
Carl Linnaeus first formally described the plant as Psoralea bituminosa. A few years later, it was moved to the genus Bituminaria, which has experienced additional changes. Today, it resides again in the genus Bituminaria, which is relatively small—it includes only 10 species.
The species is easy to identify. If you slightly crush its leaves, they emit a distinct and unpleasant smell of tar. The plant has a fascinating phytochemical composition and exhibits potent antioxidant and antibacterial properties.
Ref.:
(1) T. Nikolić, Flora Croatica, Vaskularna flora Republike Hrvatske, Vol. 2., Alfa d.d.. Zagreb (2020), p 762.
(2) W.K. Rottensteiner, Exkursionsflora für Istrien, Verlag des Naturwissenschaftlichen Vereins Kärten (2014), p 447.
(3) M. Blamey, C. Grey-Wilson, Wild Flowers of the Mediterranean, A & C Black, London (2005), p 508.
(4) Euro+Med (2006+), Euro+Med PlantBase - the information resource for Euro-Mediterranean plant diversity. www.europlusmed.org [accessed March 3. 2025]
Blueberries have a diverse range of micronutrients, with notably high levels (relative to respective Dietary Reference Intakes) of the essential dietary mineral manganese, vitamin B6, vitamin C, vitamin K and dietary fiber
One serving provides a relatively low glycemic load score of 4 out of 100 per day.
Especially in wild species, blueberries contain anthocyanins, other antioxidant pigments and various phytochemicals possibly having a role in reducing risks of some diseases, including inflammation and different cancers.
Bituminaria bituminosa (L.) C. H. Stirt., syn.: Psoralea bituminosa L., Aspalthium bituminosum (L.) Fourr., Psoralea palaestina Gouan, Asphalthium bituminosum (L.) Medik.
Family: Fabaceae
EN: Arabian Pea, Pitch Trefoil, DE: Gewöhnlicher Asphaltklee
Slo.: arabski grah
Dat.: May 21. 2007
Lat.: 45,00508 Long.: 13,81403 WGS84
Code: Bot_0189/2007_DSC8001 and DSC8037, Bot_0190/2007_DSC8116, Bot_0191/2007_DSC8228
Habitat: Dry grassland with some bushes, flat terrain, open, sunny location; elevation 125 m (410 feet); average precipitations ~ 1.000 mm/year, average temperature 13-15 deg C, Sub-Mediterranean phytogeographical region.
Substratum: soil.
Place: Croatia, Istria peninsula, approximately 4.3 km south-southeast of Bale, east of the Bale-Pula road at the intersection of the local road leading to the village of Gajana.
Comment regarding the Flick album Bituminaria bituminosa: Bituminaria bituminosa is an intriguing and relatively uncommon Mediterranean plant. It is prevalent along the coasts of the Mediterranean Sea in all countries except Syria and Egypt. To the east, it extends as far as the Caucasus and the shores of the Black Sea (Ref.: 4).
Carl Linnaeus first formally described the plant as Psoralea bituminosa. A few years later, it was moved to the genus Bituminaria, which has experienced additional changes. Today, it resides again in the genus Bituminaria, which is relatively small—it includes only 10 species.
The species is easy to identify. If you slightly crush its leaves, they emit a distinct and unpleasant smell of tar. The plant has a fascinating phytochemical composition and exhibits potent antioxidant and antibacterial properties.
Ref.:
(1) T. Nikolić, Flora Croatica, Vaskularna flora Republike Hrvatske, Vol. 2., Alfa d.d.. Zagreb (2020), p 762.
(2) W.K. Rottensteiner, Exkursionsflora für Istrien, Verlag des Naturwissenschaftlichen Vereins Kärten (2014), p 447.
(3) M. Blamey, C. Grey-Wilson, Wild Flowers of the Mediterranean, A & C Black, London (2005), p 508.
(4) Euro+Med (2006+), Euro+Med PlantBase - the information resource for Euro-Mediterranean plant diversity. www.europlusmed.org [accessed March 3. 2025]
Dahlia (UK /deɪliə/ or US /dɑːliə/) is a genus of bushy, tuberous, herbaceous perennial plants native to Mexico. A member of the Asteraceae (or Compositae), dicotyledonous plants, related species include the sunflower, daisy, chrysanthemum, and zinnia. There are 42 species of dahlia, with hybrids commonly grown as garden plants. Flower forms are variable, with one head per stem; these can be as small as 5.1 cm diameter or up to 30 cm ("dinner plate"). This great variety results from dahlias being octoploids—that is, they have eight sets of homologous chromosomes, whereas most plants have only two. In addition, dahlias also contain many transposons - genetic pieces that move from place to place upon an allele - which contributes to their manifesting such great diversity.
The stems are leafy, ranging in height from as low as 30 cm to more than 1.8–2.4 m. The majority of species do not produce scented flowers or cultivars. Like most plants that do not attract pollinating insects through scent, they are brightly colored, displaying most hues, with the exception of blue.
The dahlia was declared the national flower of Mexico in 1963. The tubers were grown as a food crop by the Aztecs, but this use largely died out after the Spanish Conquest. Attempts to introduce the tubers as a food crop in Europe were unsuccessful.
DESCRIPTION
Perennial plants, with mostly tuberous roots. While some have herbaceous stems, others have stems which lignify in the absence of secondary tissue and resprout following winter dormancy, allowing further seasons of growth. as a member of the Asteraceae the flower head is actually a composite (hence the older name Compositae) with both central disc florets and surrounding ray florets. Each floret is a flower in its own right, but is often incorrectly described as a petal, particularly by horticulturalists. The modern mame Asteraceae refers to the appearance of a star with surrounding rays.
TAXONOMY
HISTORY
EARLY HISTORY
Spaniards reported finding the plants growing in Mexico in 1525, but the earliest known description is by Francisco Hernández, physician to Philip II, who was ordered to visit Mexico in 1570 to study the "natural products of that country". They were used as a source of food by the indigenous peoples, and were both gathered in the wild and cultivated. The Aztecs used them to treat epilepsy, and employed the long hollow stem of the (Dahlia imperalis) for water pipes. The indigenous peoples variously identified the plants as "Chichipatl" (Toltecs) and "Acocotle" or "Cocoxochitl" (Aztecs). From Hernandez' perception of Aztec, to Spanish, through various other translations, the word is "water cane", "water pipe", "water pipe flower", "hollow stem flower" and "cane flower". All these refer to the hollowness of the plants' stem.Hernandez described two varieties of dahlias (the pinwheel-like Dahlia pinnata and the huge Dahlia imperialis) as well as other medicinal plants of New Spain. Francisco Dominguez, a Hidalgo gentleman who accompanied Hernandez on part of his seven-year study, made a series of drawings to supplement the four volume report. Three of his drawings showed plants with flowers: two resembled the modern bedding dahlia, and one resembled the species Dahlia merki; all displayed a high degree of doubleness. In 1578 the manuscript, entitled Nova Plantarum, Animalium et Mineralium Mexicanorum Historia, was sent back to the Escorial in Madrid; they were not translated into Latin by Francisco Ximenes until 1615. In 1640, Francisco Cesi, President of the Academia Linei of Rome, bought the Ximenes translation, and after annotating it, published it in 1649-1651 in two volumes as Rerum Medicarum Novae Hispaniae Thesaurus Seu Nova Plantarium, Animalium et Mineraliuím Mexicanorum Historia. The original manuscripts were destroyed in a fire in the mid-1600s.
EUROPEAN INTRODUCTION
In 1787, the French botanist Nicolas-Joseph Thiéry de Menonville, sent to Mexico to steal the cochineal insect valued for its scarlet dye, reported the strangely beautiful flowers he had seen growing in a garden in Oaxaca. In 1789, Vicente Cervantes, Director of the Botanical Garden at Mexico City, sent "plant parts" to Abbe Antonio José Cavanilles, Director of the Royal Gardens of Madrid. Cavanilles flowered one plant that same year, then the second one a year later. In 1791 he called the new growths "Dahlia" for Anders Dahl. The first plant was called Dahlia pinnata after its pinnate foliage; the second, Dahlia rosea for its rose-purple color. In 1796 Cavanilles flowered a third plant from the parts sent by Cervantes, which he named Dahlia coccinea for its scarlet color.In 1798, Cavanilles sent D. Pinnata seeds to Parma, Italy. That year, the Marchioness of Bute, wife of The Earl of Bute, the English Ambassador to Spain, obtained a few seeds from Cavanilles and sent them to Kew Gardens, where they flowered but were lost after two to three years. In the following years Madrid sent seeds to Berlin and Dresden in Germany, and to Turin and Thiene in Italy. In 1802, Cavanilles sent tubers of "these three" (D. pinnata, D. rosea, D. coccinea) to Swiss botanist Augustin Pyramus de Candolle at University of Montpelier in France, Andre Thouin at the Jardin des Plantes in Paris and Scottish botanist William Aiton at Kew Gardens. That same year, John Fraser, English nurseryman and later botanical collector to the Czar of Russia, brought D. coccinea seeds from Paris to the Apothecaries Gardens in England, where they flowered in his greenhouse a year later, providing Botanical Magazine with an illustration.In 1804, a new species, Dahlia sambucifolia, was successfully grown at Holland House, Kensington. Whilst in Madrid in 1804, Lady Holland was given either dahlia seeds or tubers by Cavanilles. She sent them back to England, to Lord Holland's librarian Mr Buonaiuti at Holland House, who successfully raised the plants. A year later, Buonaiuti produced two double flowers. The plants raised in 1804 did not survive; new stock was brought from France in 1815. In 1824, Lord Holland sent his wife a note containing the following verse:
"The dahlia you brought to our isle
Your praises for ever shall speak;
Mid gardens as sweet as your smile,
And in colour as bright as your cheek."
In 1805, German naturalist Alexander von Humboldt sent more seeds from Mexico to Aiton in England, Thouin in Paris, and Christoph Friedrich Otto, director of the Berlin Botanical Garden. More significantly, he sent seeds to botanist Carl Ludwig Willdenow in Germany. Willdenow now reclassified the rapidly growing number of species, changing the genus from Dahlia to Georgina; after naturalist Johann Gottlieb Georgi. He combined the Cavanilles species D. pinnata and D. rosea under the name of Georgina variabilis; D. coccinea was still held to be a separate species, which he renamed Georgina coccinea.
CLASSIFICATION
Since 1789 when Cavanilles first flowered the dahlia in Europe, there has been an ongoing effort by many growers, botanists and taxonomists, to determine the development of the dahlia to modern times. At least 85 species have been reported: approximately 25 of these were first reported from the wild, the remainder appeared in gardens in Europe. They were considered hybrids, the results of crossing between previously reported species, or developed from the seeds sent by Humboldt from Mexico in 1805, or perhaps from some other undocumented seeds that had found their way to Europe. Several of these were soon discovered to be identical with earlier reported species, but the greatest number are new varieties. Morphological variation is highly pronounced in the dahlia. William John Cooper Lawrence, who hybridized hundreds of families of dahlias in the 1920s, stated: "I have not yet seen any two plants in the families I have raised which were not to be distinguished one from the other. Constant reclassification of the 85 reported species has resulted in a considerably smaller number of distinct species, as there is a great deal of disagreement today between systematists over classification.
In 1829, all species growing in Europe were reclassified under an all-encompassing name of D. variabilis, Desf., though this is not an accepted name. Through the interspecies cross of the Humboldt seeds and the Cavanilles species, 22 new species were reported by that year, all of which had been classified in different ways by several different taxonomists, creating considerable confusion as to which species was which.
In 1830 William Smith suggested that all dahlia species could be divided into two groups for color, red-tinged and purple-tinged. In investigating this idea Lawrence determined that with the exception of D. variabilis, all dahlia species may be assigned to one of two groups for flower-colour: Group I (ivory-magenta) or Group II (yellow-orange-scarlet).
CIRCUMSCRIPTION
The genus Dahlia is situated in the Asteroideae subfamily of the Asteraceae, in the Coreopsideae tribe. Within that tribe it is the second largest genus, after Coreopsis, and appears as a well defined clade within the Coreopsideae.
SUBDIVISION
INFRAGENERIC SUBDIVISION
Sherff (1955), in the first modern taxonomy described three sections for the 18 species he recognised, Pseudodendron, Epiphytum and Dahlia. By 1969 Sørensen recognised 29 species and four sections by splitting off Entemophyllon from section Dahlia. By contrast Giannasi (1975) using a phytochemical analysis based on flavonoids, reduced the genus to just two sections, Entemophyllon and Dahlia, the latter having three subsections, Pseudodendron, Dahlia, and Merckii. Sørensen then issued a further revision in 1980, incorporating subsection Merckii in his original section Dahlia. When he described two new species in the 1980s (Dahlia tubulata and D. congestifolia), he placed them within his existing sections. A further species, Dahlia sorensenii was added by Hansen and Hjerting in (1996). At the same time they demonstrated that Dahlia pinnata should more properly be designated D. x pinnata. D. x pinnata was shown to actually be a variant of D. sorensenii that had acquired hybrid qualities before it was introduced to Europe in the sixteenth century and formally named by Cavanilles. The original wild D. pinnata is presumed extinct. Further species continue to be described, Saar (2003) describing 35 species. However separation of the sections on morphological, cytologal and biocemical criteria has not been entirely satisfactory.
To date these sectional divisions have not been fully supported phylogenetically, which demonstrate only section Entemophyllon as a distinct sectional clade. The other major grouping is the Core Dahlia Clade (CDC), which includes most of section Dahlia. The remainder of the species occupy what has been described as the Variable Root Clade (VRC) which includes the small section Pseudodendron but also the monotypic section Epiphytum and a number of species from within section Dahlia. Outside of these three clades lie D. tubulata and D. merckii as a polytomy.
Horticulturally the sections retain some usage, section Pseudodendron being referred to as 'Tree Dahlias', Epiphytum as the 'Vine Dahlia'. The remaining two herbaceous sections being distinguished by their pinnules, opposing (Dahlia) or alternating (Entemophyllon).
SECTIONS
Sections (including chromosome numbers), with geographical distribution;
- Epiphytum Sherff (2n = 32)
10 m tall climber with aerial roots 5 cm thick and up to more than 20 m long; pinnules opposite
1 species, D. macdougallii Sherff
Mexico: Oaxaca
- Entemophyllon P. D. Sorensen (2n = 34)
6 species
Mexico: Hidalgo, Nuevo León, Tamaulipas, Querétaro, Durango, San Luis Potosí
- Pseudodendron P. D. Sorensen (2n = 32)
3 species + D. excelsa of uncertain identity
Mexico: Chiapas, Guerrero, Jalisco, Michoacan, Oaxaca, and
Costa Rica, El Salvador, Guatemala & Colombia
- Dahlia (2n = 32, 36 or 64)
24 species
Mexico: Distrito Federal, Guerrero, Hidalgo, Morelos, Nuevo León, Puebla, San Luis Potosí, Tamaulipas, Veracruz, Oaxaca, Puebla, Chiapas, México, Huehuetenango, Chihuahua, Durango, Michoacan & Guatemala
Only Pseudodendron (D. imperialis) and Dahlia (D. australis, D. coccinea) occur outside Mexico.
SPECIES
There are currently 42 accepted species in the Dahlia genus, but new species continue to be described.
ETYMOLOGY
The naming of the plant itself has long been a subject of some confusion. Many sources state that the name "Dahlia" was bestowed by the pioneering Swedish botanist and taxonomist Carl Linnaeus to honor his late student, Anders Dahl, author of Observationes Botanicae. However, Linnaeus died in 1778, more than eleven years before the plant was introduced into Europe in 1789, so while it is generally agreed that the plant was named in 1791 in honor of Dahl, who had died two years before, Linnaeus could not have been the one who did so. It was probably Abbe Antonio Jose Cavanilles, Director of the Royal Gardens of Madrid, who should be credited with the attempt to scientifically define the genus, since he not only received the first specimens from Mexico in 1789, but named the first three species that flowered from the cuttings.
Regardless of who bestowed it, the name was not so easily established. In 1805, German botanist Carl Ludwig Willdenow, asserting that the genus Dahlia Thunb. (published a year after Cavanilles's genus and now considered a synonym of Trichocladus) was more widely accepted, changed the plants' genus from Dahlia to Georgina; after the German-born naturalist Johann Gottlieb Georgi, a professor at the Imperial Academy of Sciences of St. Petersburg, Russia. He also reclassified and renamed the first three species grown, and identified, by Cavanilles. It was not until 1810, in a published article, that he officially adopted the Cavanilles' original designation of Dahlia. However, the name Georgina still persisted in Germany for the next few decades.
"Dahl" is a homophone of the Swedish word "dal", or "valley"; although it is not a true translation, the plant is sometimes referred to as the "valley flower".
DISTRIBUTION AND HABITAT
Predominantly Mexico, but some species are found ranging as far south as northern South America. D. australis occurs at least as far south as southwestern Guatemala, while D. coccinea and D. imperialis also occur in parts of Central America and northern South America. Dahlia is a genus of the uplands and mountains, being found at elevations between 1,500 and 3,700 meters, in what has been described as a "pine-oak woodland" vegetative zone. Most species have limited ranges scattered throughout many mountain ranges in Mexico.
ECOLOGY
The commonest pollinators are bees and small beetles.
PESTS AND DISEASES
Slugs and snails are serious pests in some parts of the world, particularly in spring when new growth is emerging through the soil. Earwigs can also disfigure the blooms. The other main pests likely to be encountered are aphids (usually on young stems and immature flower buds), red spider mite (causing foliage mottling and discolouration, worse in hot and dry conditions) and capsid bugs (resulting in contortion and holes at growing tips). Diseases affecting dahlias include powdery mildew, grey mould (Botrytis cinerea), verticillium wilt, dahlia smut (Entyloma calendulae f. dahliae), phytophthora and some plant viruses. Dahlias are a source of food for the larvae of some Lepidoptera species including Angle Shades, Common Swift, Ghost Moth and Large Yellow Underwing.
CULTIVATION
Dahlias grow naturally in climates which do not experience frost (the tubers are hardy to USDA Zone 8), consequently they are not adapted to withstand sub-zero temperatures. However, their tuberous nature enables them to survive periods of dormancy, and this characteristic means that gardeners in temperate climates with frosts can grow dahlias successfully, provided the tubers are lifted from the ground and stored in cool yet frost-free conditions during the winter. Planting the tubers quite deep (10 – 15 cm) also provides some protection. When in active growth, modern dahlia hybrids perform most successfully in well-watered yet free-draining soils, in situations receiving plenty of sunlight. Taller cultivars usually require some form of staking as they grow, and all garden dahlias need deadheading regularly, once flowering commences.
HORTICURAL CLASSIFICATION
HISTORY
The inappropriate term D. variabilis is often used to describe the cultivars of Dahlia since the correct parentage remains obscure, but probably involves Dahlia coccinea. In 1846 the Caledonia Horticultural Society of Edinburgh offered a prize of 2,000 pounds to the first person succeeding in producing a blue dahlia. This has to date not been accomplished. While dahlias produce anthocyanin, an element necessary for the production of the blue, to achieve a true blue color in a plant, the anthocyanin delphinidin needs six hydroxyl groups. To date dahlias have only developed five, so the closest that breeders have come to achieving a "blue" specimen are variations of mauve, purples and lilac hues.
By the beginning of the twentieth century a number of different types were recognised. These terms were based on shape or colour, and the National Dahlia Society included cactus, pompon, single, show and fancy in its 1904 guide. Many national societies developed their own classification systems until 1962 when the International Horticultural Congress agreed to develop an internationally recognised system at it Brussels meeting that year, and subsequently in Maryland in 1966. This culminated in the 1969 publication of The International Register of Dahlia Names by the Royal Horticultural Society which became the central registering authority.
This system depended primarily on the visibility of the central disc, whether it was open centred or whether only ray florets were apparent centrally (double bloom). The double bloom cultivars were then subdivided according to the way in which they were folded along their longitudinal axis, flat, involute (curled inwards) or revolute (curling backwards). If the end of the ray floret was split, they were considered fimbriated. Based on these characteristics, nine groups were defined plua a tenth miscellaneous group for any cultivars not fitting the above characteristics. Fimbriated dahlias were added in 2004, and two further groups (Single and Double orchid) in 2007. The last group to be added, Peony, first appeared in 2012.
In many cases the bloom diametre was then used to further label certain groups from miniature through to giant. This practice was abandoned in 2012.
MODERN SYSTEM (RHS)
There are now more than 57,000 registered cultivars, which are officially registered through the Royal Horticultural Society (RHS). The official register is The International Register of Dahlia Names 1969 (1995 reprint) which is updated by annual supplements. The original 1969 registry published about 14,000 cultivars adding a further 1700 by 1986 and in 2003 there were 18,000. Since then about a hundred new cultivars are added annually.
FLOWER TYPE
The official RHS classification lists fourteen groups, grouped by flower type, together with the abbreviations used by the RHS;
Group 1 – Single-flowered dahlias (Sin) — Flower has a central disc with a single outer ring of florets (which may overlap) encircling it, and which may be rounded or pointed.
Group 2 – Anemone-flowered dahlias (Anem) — The centre of the flower consists of dense elongated tubular florets, longer than the disc florets of Single dahlias, while the outer parts have one or more rings of flatter ray florets. Disc absent.
Group 3 – Collerette dahlias (Col) — Large flat florets forming a single outer ring around a central disc and which may overlap a smaller circle of florets closer to the centre, which have the appearance of a collar.
Group 4 – Waterlily dahlias (WL) — Double blooms, broad sparse curved, slightly curved or flat florets and very shallow in depth compared with other dahlias. Depth less than half the diameter of the bloom. Group 5 – Decorative dahlias (D) — Double blooms, ray florets broad, flat, involute no more than seventy five per cent of the longitudinal axis, slightly twisted and usually bluntly pointed. No visible central disc.
Group 6 – Ball dahlias (Ba)— Double blooms that are ball shaped or slightly flattened. Ray florets blunt or rounded at the tips, margins arranged spirally, involute for at least seventy five percent of the length of the florets. Larger than Pompons.
Group 7 – Pompon dahlias (Pom) — Double spherical miniature flowers made up entirely from florets that are curved inwards (involute) for their entire length (longitudinal axis), resembling a pompon.
Group 8 – Cactus dahlias (C) — Double blooms, ray florets pointed, with majority revolute (rolled) over more than fifty percent of their longitudinal axis, and straight or incurved. Narrower than Semi cactus.
Group 9 – Semi cactus dahlias (S–c)— Double blooms, very pointed ray florets, revolute for greater than twenty five percent and less than fifty percent of their longitudinal axis. Broad at the base and straight or incurved, almost spiky in appearance.
Group 10 – Miscellaneous dahlias (Misc) — not described in any other group.
Group 11 – Fimbriated dahlias (Fim) — ray florets evenly split or notched into two or more divisions, uniformly throughout the bloom, creating a fimbriated (fringed) effect. The petals may be flat, involute, revolute, straight, incurving or twisted.
Group 12 – Single Orchid (Star) dahlias (SinO) — single outer ring of florets surround a central disc. The ray florets are either involute or revolute.
Group 13 – Double Orchid dahlias (DblO) — Double blooms with triangular centres. The ray florets are narrowly lanceolate and are either involute or revolute. The central disc is absent.
Group 14 – Peony-flowered dahlias (P) — Large flowers with three or four rows of rays that are flattened and expanded and arranged irregularly. The rays surround a golden disc similar to that of Single dahlias.
FLOWER SIZE
Earlier versions of the registry subdivided some groups by flower size. Groups 4, 5, 8 and 9 were divided into five subgroups (A to E) from Giant to Miniature, and Group 6 into two subgroups, Small and Miniature. Dahlias were then described by Group and Subgroup, e.g. 5(d) ‘Ace Summer Sunset’. Some Dahlia Societies have continued this practice, but this is neither official nor standardised. As of 2013 The RHS uses two size descriptors
Dwarf Bedder (Dw.B.) — not usually exceeding 600 mm in height, e.g. 'Preston Park' (Sin/DwB)
Lilliput dahlias (Lil) — not usually exceeding 300 mm in height, with single, semi-double or double florets up to 26 mm in diameter. ("baby" or "top-mix" dahlias), e.g. 'Harvest Tiny Tot' (Misc/Lil)
Sizes can range from tiny micro dahlias with flowers less than 50mm to giants that are over 250mm in diameter. The groupings listed here are from the New Zealand Society.
Giant flowered cultivars have blooms with a diameter of over 250mm.
Large flowered cultivars have blooms with a diameter between 200mm-250mm.
Medium flowered cultivars have blooms with a diameter between 155mm-200mm.
Small flowered cultivars have blooms with a diameter between 115mm-155mm.
Miniature flowered cultivars have blooms with a diameter between 50mm-115mm.
Pompom flowered cultivars have blooms with a diameter less than 50mm.
In addition to the official classification and the terminology used by various dahlia societies, individual horticulturalists use a wide range of other descriptions, such as 'Incurved' and abbreviations in their catalogues, such as CO for Collarette.
BRANDING
Some plant growers include their brand name in the cultivar name. Thus Fides (part of the Dümmen Orange Group) in the Netherlands developed a series of cultivars which they named the Dahlinova Series, for example Dahlinova 'Carolina Burgundy'. These are Group 10 Miscellaneous in the RHS classification scheme.
DOUBLE DAHLIAS
In 1805, several new species were reported with red, purple, lilac, and pale yellow coloring, and the first true double flower was produced in Belgium. One of the more popular concepts of dahlia history, and the basis for many different interpretations and confusion, is that all the original discoveries were single flowered types, which, through hybridization and selective breeding, produced double forms. Many of the species of dahlias then, and now, have single flowered blooms. coccinea, the third dahlia to bloom in Europe, was a single. But two of the three drawings of dahlias by Dominguez, made in Mexico between 1570–77, showed definite characteristics of doubling. In the early days of the dahlia in Europe, the word "double" simply designated flowers with more than one row of petals. The greatest effort was now directed to developing improved types of double dahlias.
During the years 1805 to 1810 several people claimed to have produced a double dahlia. In 1805 Henry C. Andrews made a drawing of such a plant in the collection of Lady Holland, grown from seedlings sent that year from Madrid. Like other doubles of the time it did not resemble the doubles of today. The first modern double, or full double, appeared in Belgium; M. Donckelaar, Director of the Botanic Garden at Louvain, selected plants for that characteristic, and within a few years secured three fully double forms. By 1826 double varieties were being grown almost exclusively, and there was very little interest in the single forms. Up to this time all the so-called double dahlias had been purple, or tinged with purple, and it was doubted if a variety untinged with that color was obtainable.
In 1843, scented single forms of dahlias were first reported in Neu Verbass, Austria. D. crocea, a fragrant variety grown from one of the Humboldt seeds, was probably interbred with the single D. coccinea. A new scented species would not be introduced until the next century when the D. coronata was brought from Mexico to Germany in 1907.
The exact date the dahlia was introduced in the United States is uncertain. One of the first Dahlias in the USA may be the D. coccinea speciosissima grown by Mr William Leathe, of Cambridgeport, near Boston, around 1929. According to Edward Sayers "it attracted much admiration, and at that time was considered a very elegant flower, it was however soon eclipsed by that splendid scarlet, the Countess of Liverpool". However 9 cultivars were already listed in the catalog from Thornburn, 1825. And even earlier reference can be found in a catalogue from the Linnaean Botanical Garden, New York, 1820, that includes one scarlet, one purple, and two double orange Dahlias for sale.
Sayers stated that "No person has done more for the introduction and advancement of the culture of the Dahlia than George C. Thorburn, of New York, who yearly flowers many thousand plants at his place at Hallet's Cove, near Harlaem. The show there in the flowering season is a rich treat for the lovers of floriculture : for almost every variety can be seen growing in two large blocks or masses which lead from the road to the dwelling-house, and form a complete field of the Dahlia as a foreground to the house. Mr T. Hogg, Mr William Read, and many other well known florists, have also contributed much in the vicinity of New York, to the introduction of the Dahlia. Indeed so general has become the taste that almost every garden has its show of the Dahlia in the season." In Boston too there were many collections, a collection from the Messrs Hovey of Cambridgeport was also mentioned.
In 1835 Thomas Bridgeman, published a list of 160 double dahlias in his Florist's Guide. 60 of the choicest were supplied by Mr. G. C. Thornburn of Astoria, N.Y. who got most of them from contacts in the UK. Not a few of them had taken prices "at the English and American exhibitions".
"STARS OF DEVIL"
In 1872 J.T. van der Berg of Utrecht in the Netherlands, received a shipment of seeds and plants from a friend in Mexico. The entire shipment was badly rotted and appeared to be ruined, but van der Berg examined it carefully and found a small piece of root that seemed alive. He planted and carefully tended it; it grew into a plant that he identified as a dahlia. He made cuttings from the plant during the winter of 1872-1873. This was an entirely different type of flower, with a rich, red color and a high degree of doubling. In 1874 van der Berg catalogued it for sale, calling it Dahlia juarezii to honor Mexican President Benito Pablo Juarez, who had died the year before, and described it as "...equal to the beautiful color of the red poppy. Its form is very outstanding and different in every respect of all known dahlia flowers.".
This plant has perhaps had a greater influence on the popularity of the modern dahlia than any other. Called "Les Etoiles de Diable" (Stars of the Devil) in France and "Cactus dahlia" elsewhere, the edges of its petals rolled backwards, rather than forward, and this new form revolutionized the dahlia world. It was thought to be a distinct mutation since no other plant that resembled it could be found in the wild. Today it is assumed that D. juarezii had, at one time, existed in Mexico and subsequently disappeared. Nurserymen in Europe crossbred this plant with dahlias discovered earlier; the results became the progenitors of all modern dahlia hybrids today.
AWARD OF GARDEN MERIT (RHS)
As of 2015, 124 dahlia cultivars have gained the Royal Horticultural Society's Award of Garden Merit:
"Bednall beauty"
"Bishop of Llandaff"
"Clair de lune"
"David Howard"
"Ellen Huston"
"Fascination"
"Gallery art deco"
"Gallery Art Nouveau"
"Glorie van Heemstede"
"Honka"
"Moonfire"
"Twyning's After Eight"
USES
FLORICULTURE
The asterid eudicots contain two economically important geophyte genera, Dahlia and Liatris. Horticulturally the garden dahlia is usually treated as the cultigen D. variabilis Hort., which while being responsible for thousands of cultivars has an obscure taxonomic status.
OTHER
Today the dahlia is still considered one of the native ingredients in Oaxacan cuisine; several cultivars are still grown especially for their large, sweet potato-like tubers. Dacopa, an intense mocha-tasting extract from the roasted tubers, is used to flavor beverages throughout Central America.
In Europe and America, prior to the discovery of insulin in 1923, diabetics - as well as consumptives - were often given a substance called Atlantic starch or diabetic sugar, derived from inulin, a naturally occurring form of fruit sugar, extracted from dahlia tubers. Inulin is still used in clinical tests for kidney functionality.
WIKIPEDIA
Dahlia (UK /deɪliə/ or US /dɑːliə/) is a genus of bushy, tuberous, herbaceous perennial plants native to Mexico. A member of the Asteraceae (or Compositae), dicotyledonous plants, related species include the sunflower, daisy, chrysanthemum, and zinnia. There are 42 species of dahlia, with hybrids commonly grown as garden plants. Flower forms are variable, with one head per stem; these can be as small as 5.1 cm diameter or up to 30 cm ("dinner plate"). This great variety results from dahlias being octoploids—that is, they have eight sets of homologous chromosomes, whereas most plants have only two. In addition, dahlias also contain many transposons - genetic pieces that move from place to place upon an allele - which contributes to their manifesting such great diversity.
The stems are leafy, ranging in height from as low as 30 cm to more than 1.8–2.4 m. The majority of species do not produce scented flowers or cultivars. Like most plants that do not attract pollinating insects through scent, they are brightly colored, displaying most hues, with the exception of blue.
The dahlia was declared the national flower of Mexico in 1963. The tubers were grown as a food crop by the Aztecs, but this use largely died out after the Spanish Conquest. Attempts to introduce the tubers as a food crop in Europe were unsuccessful.
DESCRIPTION
Perennial plants, with mostly tuberous roots. While some have herbaceous stems, others have stems which lignify in the absence of secondary tissue and resprout following winter dormancy, allowing further seasons of growth. as a member of the Asteraceae the flower head is actually a composite (hence the older name Compositae) with both central disc florets and surrounding ray florets. Each floret is a flower in its own right, but is often incorrectly described as a petal, particularly by horticulturalists. The modern mame Asteraceae refers to the appearance of a star with surrounding rays.
TAXONOMY
HISTORY
EARLY HISTORY
Spaniards reported finding the plants growing in Mexico in 1525, but the earliest known description is by Francisco Hernández, physician to Philip II, who was ordered to visit Mexico in 1570 to study the "natural products of that country". They were used as a source of food by the indigenous peoples, and were both gathered in the wild and cultivated. The Aztecs used them to treat epilepsy, and employed the long hollow stem of the (Dahlia imperalis) for water pipes. The indigenous peoples variously identified the plants as "Chichipatl" (Toltecs) and "Acocotle" or "Cocoxochitl" (Aztecs). From Hernandez' perception of Aztec, to Spanish, through various other translations, the word is "water cane", "water pipe", "water pipe flower", "hollow stem flower" and "cane flower". All these refer to the hollowness of the plants' stem.Hernandez described two varieties of dahlias (the pinwheel-like Dahlia pinnata and the huge Dahlia imperialis) as well as other medicinal plants of New Spain. Francisco Dominguez, a Hidalgo gentleman who accompanied Hernandez on part of his seven-year study, made a series of drawings to supplement the four volume report. Three of his drawings showed plants with flowers: two resembled the modern bedding dahlia, and one resembled the species Dahlia merki; all displayed a high degree of doubleness. In 1578 the manuscript, entitled Nova Plantarum, Animalium et Mineralium Mexicanorum Historia, was sent back to the Escorial in Madrid; they were not translated into Latin by Francisco Ximenes until 1615. In 1640, Francisco Cesi, President of the Academia Linei of Rome, bought the Ximenes translation, and after annotating it, published it in 1649-1651 in two volumes as Rerum Medicarum Novae Hispaniae Thesaurus Seu Nova Plantarium, Animalium et Mineraliuím Mexicanorum Historia. The original manuscripts were destroyed in a fire in the mid-1600s.
EUROPEAN INTRODUCTION
In 1787, the French botanist Nicolas-Joseph Thiéry de Menonville, sent to Mexico to steal the cochineal insect valued for its scarlet dye, reported the strangely beautiful flowers he had seen growing in a garden in Oaxaca. In 1789, Vicente Cervantes, Director of the Botanical Garden at Mexico City, sent "plant parts" to Abbe Antonio José Cavanilles, Director of the Royal Gardens of Madrid. Cavanilles flowered one plant that same year, then the second one a year later. In 1791 he called the new growths "Dahlia" for Anders Dahl. The first plant was called Dahlia pinnata after its pinnate foliage; the second, Dahlia rosea for its rose-purple color. In 1796 Cavanilles flowered a third plant from the parts sent by Cervantes, which he named Dahlia coccinea for its scarlet color.In 1798, Cavanilles sent D. Pinnata seeds to Parma, Italy. That year, the Marchioness of Bute, wife of The Earl of Bute, the English Ambassador to Spain, obtained a few seeds from Cavanilles and sent them to Kew Gardens, where they flowered but were lost after two to three years. In the following years Madrid sent seeds to Berlin and Dresden in Germany, and to Turin and Thiene in Italy. In 1802, Cavanilles sent tubers of "these three" (D. pinnata, D. rosea, D. coccinea) to Swiss botanist Augustin Pyramus de Candolle at University of Montpelier in France, Andre Thouin at the Jardin des Plantes in Paris and Scottish botanist William Aiton at Kew Gardens. That same year, John Fraser, English nurseryman and later botanical collector to the Czar of Russia, brought D. coccinea seeds from Paris to the Apothecaries Gardens in England, where they flowered in his greenhouse a year later, providing Botanical Magazine with an illustration.In 1804, a new species, Dahlia sambucifolia, was successfully grown at Holland House, Kensington. Whilst in Madrid in 1804, Lady Holland was given either dahlia seeds or tubers by Cavanilles. She sent them back to England, to Lord Holland's librarian Mr Buonaiuti at Holland House, who successfully raised the plants. A year later, Buonaiuti produced two double flowers. The plants raised in 1804 did not survive; new stock was brought from France in 1815. In 1824, Lord Holland sent his wife a note containing the following verse:
"The dahlia you brought to our isle
Your praises for ever shall speak;
Mid gardens as sweet as your smile,
And in colour as bright as your cheek."
In 1805, German naturalist Alexander von Humboldt sent more seeds from Mexico to Aiton in England, Thouin in Paris, and Christoph Friedrich Otto, director of the Berlin Botanical Garden. More significantly, he sent seeds to botanist Carl Ludwig Willdenow in Germany. Willdenow now reclassified the rapidly growing number of species, changing the genus from Dahlia to Georgina; after naturalist Johann Gottlieb Georgi. He combined the Cavanilles species D. pinnata and D. rosea under the name of Georgina variabilis; D. coccinea was still held to be a separate species, which he renamed Georgina coccinea.
CLASSIFICATION
Since 1789 when Cavanilles first flowered the dahlia in Europe, there has been an ongoing effort by many growers, botanists and taxonomists, to determine the development of the dahlia to modern times. At least 85 species have been reported: approximately 25 of these were first reported from the wild, the remainder appeared in gardens in Europe. They were considered hybrids, the results of crossing between previously reported species, or developed from the seeds sent by Humboldt from Mexico in 1805, or perhaps from some other undocumented seeds that had found their way to Europe. Several of these were soon discovered to be identical with earlier reported species, but the greatest number are new varieties. Morphological variation is highly pronounced in the dahlia. William John Cooper Lawrence, who hybridized hundreds of families of dahlias in the 1920s, stated: "I have not yet seen any two plants in the families I have raised which were not to be distinguished one from the other. Constant reclassification of the 85 reported species has resulted in a considerably smaller number of distinct species, as there is a great deal of disagreement today between systematists over classification.
In 1829, all species growing in Europe were reclassified under an all-encompassing name of D. variabilis, Desf., though this is not an accepted name. Through the interspecies cross of the Humboldt seeds and the Cavanilles species, 22 new species were reported by that year, all of which had been classified in different ways by several different taxonomists, creating considerable confusion as to which species was which.
In 1830 William Smith suggested that all dahlia species could be divided into two groups for color, red-tinged and purple-tinged. In investigating this idea Lawrence determined that with the exception of D. variabilis, all dahlia species may be assigned to one of two groups for flower-colour: Group I (ivory-magenta) or Group II (yellow-orange-scarlet).
CIRCUMSCRIPTION
The genus Dahlia is situated in the Asteroideae subfamily of the Asteraceae, in the Coreopsideae tribe. Within that tribe it is the second largest genus, after Coreopsis, and appears as a well defined clade within the Coreopsideae.
SUBDIVISION
INFRAGENERIC SUBDIVISION
Sherff (1955), in the first modern taxonomy described three sections for the 18 species he recognised, Pseudodendron, Epiphytum and Dahlia. By 1969 Sørensen recognised 29 species and four sections by splitting off Entemophyllon from section Dahlia. By contrast Giannasi (1975) using a phytochemical analysis based on flavonoids, reduced the genus to just two sections, Entemophyllon and Dahlia, the latter having three subsections, Pseudodendron, Dahlia, and Merckii. Sørensen then issued a further revision in 1980, incorporating subsection Merckii in his original section Dahlia. When he described two new species in the 1980s (Dahlia tubulata and D. congestifolia), he placed them within his existing sections. A further species, Dahlia sorensenii was added by Hansen and Hjerting in (1996). At the same time they demonstrated that Dahlia pinnata should more properly be designated D. x pinnata. D. x pinnata was shown to actually be a variant of D. sorensenii that had acquired hybrid qualities before it was introduced to Europe in the sixteenth century and formally named by Cavanilles. The original wild D. pinnata is presumed extinct. Further species continue to be described, Saar (2003) describing 35 species. However separation of the sections on morphological, cytologal and biocemical criteria has not been entirely satisfactory.
To date these sectional divisions have not been fully supported phylogenetically, which demonstrate only section Entemophyllon as a distinct sectional clade. The other major grouping is the Core Dahlia Clade (CDC), which includes most of section Dahlia. The remainder of the species occupy what has been described as the Variable Root Clade (VRC) which includes the small section Pseudodendron but also the monotypic section Epiphytum and a number of species from within section Dahlia. Outside of these three clades lie D. tubulata and D. merckii as a polytomy.
Horticulturally the sections retain some usage, section Pseudodendron being referred to as 'Tree Dahlias', Epiphytum as the 'Vine Dahlia'. The remaining two herbaceous sections being distinguished by their pinnules, opposing (Dahlia) or alternating (Entemophyllon).
SECTIONS
Sections (including chromosome numbers), with geographical distribution;
- Epiphytum Sherff (2n = 32)
10 m tall climber with aerial roots 5 cm thick and up to more than 20 m long; pinnules opposite
1 species, D. macdougallii Sherff
Mexico: Oaxaca
- Entemophyllon P. D. Sorensen (2n = 34)
6 species
Mexico: Hidalgo, Nuevo León, Tamaulipas, Querétaro, Durango, San Luis Potosí
- Pseudodendron P. D. Sorensen (2n = 32)
3 species + D. excelsa of uncertain identity
Mexico: Chiapas, Guerrero, Jalisco, Michoacan, Oaxaca, and
Costa Rica, El Salvador, Guatemala & Colombia
- Dahlia (2n = 32, 36 or 64)
24 species
Mexico: Distrito Federal, Guerrero, Hidalgo, Morelos, Nuevo León, Puebla, San Luis Potosí, Tamaulipas, Veracruz, Oaxaca, Puebla, Chiapas, México, Huehuetenango, Chihuahua, Durango, Michoacan & Guatemala
Only Pseudodendron (D. imperialis) and Dahlia (D. australis, D. coccinea) occur outside Mexico.
SPECIES
There are currently 42 accepted species in the Dahlia genus, but new species continue to be described.
ETYMOLOGY
The naming of the plant itself has long been a subject of some confusion. Many sources state that the name "Dahlia" was bestowed by the pioneering Swedish botanist and taxonomist Carl Linnaeus to honor his late student, Anders Dahl, author of Observationes Botanicae. However, Linnaeus died in 1778, more than eleven years before the plant was introduced into Europe in 1789, so while it is generally agreed that the plant was named in 1791 in honor of Dahl, who had died two years before, Linnaeus could not have been the one who did so. It was probably Abbe Antonio Jose Cavanilles, Director of the Royal Gardens of Madrid, who should be credited with the attempt to scientifically define the genus, since he not only received the first specimens from Mexico in 1789, but named the first three species that flowered from the cuttings.
Regardless of who bestowed it, the name was not so easily established. In 1805, German botanist Carl Ludwig Willdenow, asserting that the genus Dahlia Thunb. (published a year after Cavanilles's genus and now considered a synonym of Trichocladus) was more widely accepted, changed the plants' genus from Dahlia to Georgina; after the German-born naturalist Johann Gottlieb Georgi, a professor at the Imperial Academy of Sciences of St. Petersburg, Russia. He also reclassified and renamed the first three species grown, and identified, by Cavanilles. It was not until 1810, in a published article, that he officially adopted the Cavanilles' original designation of Dahlia. However, the name Georgina still persisted in Germany for the next few decades.
"Dahl" is a homophone of the Swedish word "dal", or "valley"; although it is not a true translation, the plant is sometimes referred to as the "valley flower".
DISTRIBUTION AND HABITAT
Predominantly Mexico, but some species are found ranging as far south as northern South America. D. australis occurs at least as far south as southwestern Guatemala, while D. coccinea and D. imperialis also occur in parts of Central America and northern South America. Dahlia is a genus of the uplands and mountains, being found at elevations between 1,500 and 3,700 meters, in what has been described as a "pine-oak woodland" vegetative zone. Most species have limited ranges scattered throughout many mountain ranges in Mexico.
ECOLOGY
The commonest pollinators are bees and small beetles.
PESTS AND DISEASES
Slugs and snails are serious pests in some parts of the world, particularly in spring when new growth is emerging through the soil. Earwigs can also disfigure the blooms. The other main pests likely to be encountered are aphids (usually on young stems and immature flower buds), red spider mite (causing foliage mottling and discolouration, worse in hot and dry conditions) and capsid bugs (resulting in contortion and holes at growing tips). Diseases affecting dahlias include powdery mildew, grey mould (Botrytis cinerea), verticillium wilt, dahlia smut (Entyloma calendulae f. dahliae), phytophthora and some plant viruses. Dahlias are a source of food for the larvae of some Lepidoptera species including Angle Shades, Common Swift, Ghost Moth and Large Yellow Underwing.
CULTIVATION
Dahlias grow naturally in climates which do not experience frost (the tubers are hardy to USDA Zone 8), consequently they are not adapted to withstand sub-zero temperatures. However, their tuberous nature enables them to survive periods of dormancy, and this characteristic means that gardeners in temperate climates with frosts can grow dahlias successfully, provided the tubers are lifted from the ground and stored in cool yet frost-free conditions during the winter. Planting the tubers quite deep (10 – 15 cm) also provides some protection. When in active growth, modern dahlia hybrids perform most successfully in well-watered yet free-draining soils, in situations receiving plenty of sunlight. Taller cultivars usually require some form of staking as they grow, and all garden dahlias need deadheading regularly, once flowering commences.
HORTICURAL CLASSIFICATION
HISTORY
The inappropriate term D. variabilis is often used to describe the cultivars of Dahlia since the correct parentage remains obscure, but probably involves Dahlia coccinea. In 1846 the Caledonia Horticultural Society of Edinburgh offered a prize of 2,000 pounds to the first person succeeding in producing a blue dahlia. This has to date not been accomplished. While dahlias produce anthocyanin, an element necessary for the production of the blue, to achieve a true blue color in a plant, the anthocyanin delphinidin needs six hydroxyl groups. To date dahlias have only developed five, so the closest that breeders have come to achieving a "blue" specimen are variations of mauve, purples and lilac hues.
By the beginning of the twentieth century a number of different types were recognised. These terms were based on shape or colour, and the National Dahlia Society included cactus, pompon, single, show and fancy in its 1904 guide. Many national societies developed their own classification systems until 1962 when the International Horticultural Congress agreed to develop an internationally recognised system at it Brussels meeting that year, and subsequently in Maryland in 1966. This culminated in the 1969 publication of The International Register of Dahlia Names by the Royal Horticultural Society which became the central registering authority.
This system depended primarily on the visibility of the central disc, whether it was open centred or whether only ray florets were apparent centrally (double bloom). The double bloom cultivars were then subdivided according to the way in which they were folded along their longitudinal axis, flat, involute (curled inwards) or revolute (curling backwards). If the end of the ray floret was split, they were considered fimbriated. Based on these characteristics, nine groups were defined plua a tenth miscellaneous group for any cultivars not fitting the above characteristics. Fimbriated dahlias were added in 2004, and two further groups (Single and Double orchid) in 2007. The last group to be added, Peony, first appeared in 2012.
In many cases the bloom diametre was then used to further label certain groups from miniature through to giant. This practice was abandoned in 2012.
MODERN SYSTEM (RHS)
There are now more than 57,000 registered cultivars, which are officially registered through the Royal Horticultural Society (RHS). The official register is The International Register of Dahlia Names 1969 (1995 reprint) which is updated by annual supplements. The original 1969 registry published about 14,000 cultivars adding a further 1700 by 1986 and in 2003 there were 18,000. Since then about a hundred new cultivars are added annually.
FLOWER TYPE
The official RHS classification lists fourteen groups, grouped by flower type, together with the abbreviations used by the RHS;
Group 1 – Single-flowered dahlias (Sin) — Flower has a central disc with a single outer ring of florets (which may overlap) encircling it, and which may be rounded or pointed.
Group 2 – Anemone-flowered dahlias (Anem) — The centre of the flower consists of dense elongated tubular florets, longer than the disc florets of Single dahlias, while the outer parts have one or more rings of flatter ray florets. Disc absent.
Group 3 – Collerette dahlias (Col) — Large flat florets forming a single outer ring around a central disc and which may overlap a smaller circle of florets closer to the centre, which have the appearance of a collar.
Group 4 – Waterlily dahlias (WL) — Double blooms, broad sparse curved, slightly curved or flat florets and very shallow in depth compared with other dahlias. Depth less than half the diameter of the bloom. Group 5 – Decorative dahlias (D) — Double blooms, ray florets broad, flat, involute no more than seventy five per cent of the longitudinal axis, slightly twisted and usually bluntly pointed. No visible central disc.
Group 6 – Ball dahlias (Ba)— Double blooms that are ball shaped or slightly flattened. Ray florets blunt or rounded at the tips, margins arranged spirally, involute for at least seventy five percent of the length of the florets. Larger than Pompons.
Group 7 – Pompon dahlias (Pom) — Double spherical miniature flowers made up entirely from florets that are curved inwards (involute) for their entire length (longitudinal axis), resembling a pompon.
Group 8 – Cactus dahlias (C) — Double blooms, ray florets pointed, with majority revolute (rolled) over more than fifty percent of their longitudinal axis, and straight or incurved. Narrower than Semi cactus.
Group 9 – Semi cactus dahlias (S–c)— Double blooms, very pointed ray florets, revolute for greater than twenty five percent and less than fifty percent of their longitudinal axis. Broad at the base and straight or incurved, almost spiky in appearance.
Group 10 – Miscellaneous dahlias (Misc) — not described in any other group.
Group 11 – Fimbriated dahlias (Fim) — ray florets evenly split or notched into two or more divisions, uniformly throughout the bloom, creating a fimbriated (fringed) effect. The petals may be flat, involute, revolute, straight, incurving or twisted.
Group 12 – Single Orchid (Star) dahlias (SinO) — single outer ring of florets surround a central disc. The ray florets are either involute or revolute.
Group 13 – Double Orchid dahlias (DblO) — Double blooms with triangular centres. The ray florets are narrowly lanceolate and are either involute or revolute. The central disc is absent.
Group 14 – Peony-flowered dahlias (P) — Large flowers with three or four rows of rays that are flattened and expanded and arranged irregularly. The rays surround a golden disc similar to that of Single dahlias.
FLOWER SIZE
Earlier versions of the registry subdivided some groups by flower size. Groups 4, 5, 8 and 9 were divided into five subgroups (A to E) from Giant to Miniature, and Group 6 into two subgroups, Small and Miniature. Dahlias were then described by Group and Subgroup, e.g. 5(d) ‘Ace Summer Sunset’. Some Dahlia Societies have continued this practice, but this is neither official nor standardised. As of 2013 The RHS uses two size descriptors
Dwarf Bedder (Dw.B.) — not usually exceeding 600 mm in height, e.g. 'Preston Park' (Sin/DwB)
Lilliput dahlias (Lil) — not usually exceeding 300 mm in height, with single, semi-double or double florets up to 26 mm in diameter. ("baby" or "top-mix" dahlias), e.g. 'Harvest Tiny Tot' (Misc/Lil)
Sizes can range from tiny micro dahlias with flowers less than 50mm to giants that are over 250mm in diameter. The groupings listed here are from the New Zealand Society.
Giant flowered cultivars have blooms with a diameter of over 250mm.
Large flowered cultivars have blooms with a diameter between 200mm-250mm.
Medium flowered cultivars have blooms with a diameter between 155mm-200mm.
Small flowered cultivars have blooms with a diameter between 115mm-155mm.
Miniature flowered cultivars have blooms with a diameter between 50mm-115mm.
Pompom flowered cultivars have blooms with a diameter less than 50mm.
In addition to the official classification and the terminology used by various dahlia societies, individual horticulturalists use a wide range of other descriptions, such as 'Incurved' and abbreviations in their catalogues, such as CO for Collarette.
BRANDING
Some plant growers include their brand name in the cultivar name. Thus Fides (part of the Dümmen Orange Group) in the Netherlands developed a series of cultivars which they named the Dahlinova Series, for example Dahlinova 'Carolina Burgundy'. These are Group 10 Miscellaneous in the RHS classification scheme.
DOUBLE DAHLIAS
In 1805, several new species were reported with red, purple, lilac, and pale yellow coloring, and the first true double flower was produced in Belgium. One of the more popular concepts of dahlia history, and the basis for many different interpretations and confusion, is that all the original discoveries were single flowered types, which, through hybridization and selective breeding, produced double forms. Many of the species of dahlias then, and now, have single flowered blooms. coccinea, the third dahlia to bloom in Europe, was a single. But two of the three drawings of dahlias by Dominguez, made in Mexico between 1570–77, showed definite characteristics of doubling. In the early days of the dahlia in Europe, the word "double" simply designated flowers with more than one row of petals. The greatest effort was now directed to developing improved types of double dahlias.
During the years 1805 to 1810 several people claimed to have produced a double dahlia. In 1805 Henry C. Andrews made a drawing of such a plant in the collection of Lady Holland, grown from seedlings sent that year from Madrid. Like other doubles of the time it did not resemble the doubles of today. The first modern double, or full double, appeared in Belgium; M. Donckelaar, Director of the Botanic Garden at Louvain, selected plants for that characteristic, and within a few years secured three fully double forms. By 1826 double varieties were being grown almost exclusively, and there was very little interest in the single forms. Up to this time all the so-called double dahlias had been purple, or tinged with purple, and it was doubted if a variety untinged with that color was obtainable.
In 1843, scented single forms of dahlias were first reported in Neu Verbass, Austria. D. crocea, a fragrant variety grown from one of the Humboldt seeds, was probably interbred with the single D. coccinea. A new scented species would not be introduced until the next century when the D. coronata was brought from Mexico to Germany in 1907.
The exact date the dahlia was introduced in the United States is uncertain. One of the first Dahlias in the USA may be the D. coccinea speciosissima grown by Mr William Leathe, of Cambridgeport, near Boston, around 1929. According to Edward Sayers "it attracted much admiration, and at that time was considered a very elegant flower, it was however soon eclipsed by that splendid scarlet, the Countess of Liverpool". However 9 cultivars were already listed in the catalog from Thornburn, 1825. And even earlier reference can be found in a catalogue from the Linnaean Botanical Garden, New York, 1820, that includes one scarlet, one purple, and two double orange Dahlias for sale.
Sayers stated that "No person has done more for the introduction and advancement of the culture of the Dahlia than George C. Thorburn, of New York, who yearly flowers many thousand plants at his place at Hallet's Cove, near Harlaem. The show there in the flowering season is a rich treat for the lovers of floriculture : for almost every variety can be seen growing in two large blocks or masses which lead from the road to the dwelling-house, and form a complete field of the Dahlia as a foreground to the house. Mr T. Hogg, Mr William Read, and many other well known florists, have also contributed much in the vicinity of New York, to the introduction of the Dahlia. Indeed so general has become the taste that almost every garden has its show of the Dahlia in the season." In Boston too there were many collections, a collection from the Messrs Hovey of Cambridgeport was also mentioned.
In 1835 Thomas Bridgeman, published a list of 160 double dahlias in his Florist's Guide. 60 of the choicest were supplied by Mr. G. C. Thornburn of Astoria, N.Y. who got most of them from contacts in the UK. Not a few of them had taken prices "at the English and American exhibitions".
"STARS OF DEVIL"
In 1872 J.T. van der Berg of Utrecht in the Netherlands, received a shipment of seeds and plants from a friend in Mexico. The entire shipment was badly rotted and appeared to be ruined, but van der Berg examined it carefully and found a small piece of root that seemed alive. He planted and carefully tended it; it grew into a plant that he identified as a dahlia. He made cuttings from the plant during the winter of 1872-1873. This was an entirely different type of flower, with a rich, red color and a high degree of doubling. In 1874 van der Berg catalogued it for sale, calling it Dahlia juarezii to honor Mexican President Benito Pablo Juarez, who had died the year before, and described it as "...equal to the beautiful color of the red poppy. Its form is very outstanding and different in every respect of all known dahlia flowers.".
This plant has perhaps had a greater influence on the popularity of the modern dahlia than any other. Called "Les Etoiles de Diable" (Stars of the Devil) in France and "Cactus dahlia" elsewhere, the edges of its petals rolled backwards, rather than forward, and this new form revolutionized the dahlia world. It was thought to be a distinct mutation since no other plant that resembled it could be found in the wild. Today it is assumed that D. juarezii had, at one time, existed in Mexico and subsequently disappeared. Nurserymen in Europe crossbred this plant with dahlias discovered earlier; the results became the progenitors of all modern dahlia hybrids today.
AWARD OF GARDEN MERIT (RHS)
As of 2015, 124 dahlia cultivars have gained the Royal Horticultural Society's Award of Garden Merit:
"Bednall beauty"
"Bishop of Llandaff"
"Clair de lune"
"David Howard"
"Ellen Huston"
"Fascination"
"Gallery art deco"
"Gallery Art Nouveau"
"Glorie van Heemstede"
"Honka"
"Moonfire"
"Twyning's After Eight"
USES
FLORICULTURE
The asterid eudicots contain two economically important geophyte genera, Dahlia and Liatris. Horticulturally the garden dahlia is usually treated as the cultigen D. variabilis Hort., which while being responsible for thousands of cultivars has an obscure taxonomic status.
OTHER
Today the dahlia is still considered one of the native ingredients in Oaxacan cuisine; several cultivars are still grown especially for their large, sweet potato-like tubers. Dacopa, an intense mocha-tasting extract from the roasted tubers, is used to flavor beverages throughout Central America.
In Europe and America, prior to the discovery of insulin in 1923, diabetics - as well as consumptives - were often given a substance called Atlantic starch or diabetic sugar, derived from inulin, a naturally occurring form of fruit sugar, extracted from dahlia tubers. Inulin is still used in clinical tests for kidney functionality.
WIKIPEDIA
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What exactly is St John’s Wort?
Components of Hypericum perforatum L. (St John’s wort) now are properly contending for rank as a standardized antidepressant remedy. Due to this, excellent energy has been dedicated to determining the active antidepressant substances in the extract. From a phytochemical perspective, St John’s wort is among the best-investigated therapeutic herbs. Scientists in European countries have researched St John’s Wort for many years. They found a mixture of substances in the plant, primary of which is “hypericin", interact with particular substances in the human brain to control emotionally charged distress, help with despression symptoms, and relax the neural system. Working very much like the common synthetic prescription antidepressants (maprotiline hydrochloride and imipramine), natural extracts from St. John’s Wort have shown to relax and soothe the psyche with minimal side effectsSt John’s Wort Benefits
St. Johns Wort today has been found to be very beneficial in healing wounds and is especially good for dirty, septic wounds. St. Johns Wort has been used in case of putrid leg ulcers, that noting heals. Like the leach that was used not too many years ago for wound cleansing it does not destroy the healthy tissues and healthy cells but it cleans the dirt out of septic wounds. It helps reduce the inflammation in septic sores, in boils, in cellulite and lymhangitis.
The compound Hypericin was isolated from St. Johns Wort in 1942 and has been used as an anti-depressant for emotionally disturbed people. This tranquilizing quality from small quantities hypericin increase blood flow to stressed tissue. There is a reduced capillary fragility and enhanced uterine tone due to the increased Hypotensive blood flow.St John’s Wort Side Effects
The use of St. Johns Wort has been shown to demonstrate a side effect producing a photosensitivity. Hypericin is absorbed in the intestines and concentrates near the skin. An allergic reaction takes place when those with light fair skin are exposed sunlight. That exposure causes tissue damage and in some cases death has resulted. While taking St. Johns Wort one should avoid strong sunlight whether the skin is dark or light. There is a photosensitizing substance produced under the skin by this exposure to sunlight that causes the skin to burn.Benefits
• relieves mild to moderate depression and anxiety.
• promotes restful sleep.
• improves capillary circulation.
• increases cardiac circulation.
• eases gastrointestinal distress.
• relieves discomfort associated with premenstrual syndrome.
• fights retroviruses.
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Dahlia (UK /deɪliə/ or US /dɑːliə/) is a genus of bushy, tuberous, herbaceous perennial plants native to Mexico. A member of the Asteraceae (or Compositae), dicotyledonous plants, related species include the sunflower, daisy, chrysanthemum, and zinnia. There are 42 species of dahlia, with hybrids commonly grown as garden plants. Flower forms are variable, with one head per stem; these can be as small as 5.1 cm diameter or up to 30 cm ("dinner plate"). This great variety results from dahlias being octoploids—that is, they have eight sets of homologous chromosomes, whereas most plants have only two. In addition, dahlias also contain many transposons - genetic pieces that move from place to place upon an allele - which contributes to their manifesting such great diversity.
The stems are leafy, ranging in height from as low as 30 cm to more than 1.8–2.4 m. The majority of species do not produce scented flowers or cultivars. Like most plants that do not attract pollinating insects through scent, they are brightly colored, displaying most hues, with the exception of blue.
The dahlia was declared the national flower of Mexico in 1963. The tubers were grown as a food crop by the Aztecs, but this use largely died out after the Spanish Conquest. Attempts to introduce the tubers as a food crop in Europe were unsuccessful.
DESCRIPTION
Perennial plants, with mostly tuberous roots. While some have herbaceous stems, others have stems which lignify in the absence of secondary tissue and resprout following winter dormancy, allowing further seasons of growth. as a member of the Asteraceae the flower head is actually a composite (hence the older name Compositae) with both central disc florets and surrounding ray florets. Each floret is a flower in its own right, but is often incorrectly described as a petal, particularly by horticulturalists. The modern mame Asteraceae refers to the appearance of a star with surrounding rays.
TAXONOMY
HISTORY
EARLY HISTORY
Spaniards reported finding the plants growing in Mexico in 1525, but the earliest known description is by Francisco Hernández, physician to Philip II, who was ordered to visit Mexico in 1570 to study the "natural products of that country". They were used as a source of food by the indigenous peoples, and were both gathered in the wild and cultivated. The Aztecs used them to treat epilepsy, and employed the long hollow stem of the (Dahlia imperalis) for water pipes. The indigenous peoples variously identified the plants as "Chichipatl" (Toltecs) and "Acocotle" or "Cocoxochitl" (Aztecs). From Hernandez' perception of Aztec, to Spanish, through various other translations, the word is "water cane", "water pipe", "water pipe flower", "hollow stem flower" and "cane flower". All these refer to the hollowness of the plants' stem.Hernandez described two varieties of dahlias (the pinwheel-like Dahlia pinnata and the huge Dahlia imperialis) as well as other medicinal plants of New Spain. Francisco Dominguez, a Hidalgo gentleman who accompanied Hernandez on part of his seven-year study, made a series of drawings to supplement the four volume report. Three of his drawings showed plants with flowers: two resembled the modern bedding dahlia, and one resembled the species Dahlia merki; all displayed a high degree of doubleness. In 1578 the manuscript, entitled Nova Plantarum, Animalium et Mineralium Mexicanorum Historia, was sent back to the Escorial in Madrid; they were not translated into Latin by Francisco Ximenes until 1615. In 1640, Francisco Cesi, President of the Academia Linei of Rome, bought the Ximenes translation, and after annotating it, published it in 1649-1651 in two volumes as Rerum Medicarum Novae Hispaniae Thesaurus Seu Nova Plantarium, Animalium et Mineraliuím Mexicanorum Historia. The original manuscripts were destroyed in a fire in the mid-1600s.
EUROPEAN INTRODUCTION
In 1787, the French botanist Nicolas-Joseph Thiéry de Menonville, sent to Mexico to steal the cochineal insect valued for its scarlet dye, reported the strangely beautiful flowers he had seen growing in a garden in Oaxaca. In 1789, Vicente Cervantes, Director of the Botanical Garden at Mexico City, sent "plant parts" to Abbe Antonio José Cavanilles, Director of the Royal Gardens of Madrid. Cavanilles flowered one plant that same year, then the second one a year later. In 1791 he called the new growths "Dahlia" for Anders Dahl. The first plant was called Dahlia pinnata after its pinnate foliage; the second, Dahlia rosea for its rose-purple color. In 1796 Cavanilles flowered a third plant from the parts sent by Cervantes, which he named Dahlia coccinea for its scarlet color.In 1798, Cavanilles sent D. Pinnata seeds to Parma, Italy. That year, the Marchioness of Bute, wife of The Earl of Bute, the English Ambassador to Spain, obtained a few seeds from Cavanilles and sent them to Kew Gardens, where they flowered but were lost after two to three years. In the following years Madrid sent seeds to Berlin and Dresden in Germany, and to Turin and Thiene in Italy. In 1802, Cavanilles sent tubers of "these three" (D. pinnata, D. rosea, D. coccinea) to Swiss botanist Augustin Pyramus de Candolle at University of Montpelier in France, Andre Thouin at the Jardin des Plantes in Paris and Scottish botanist William Aiton at Kew Gardens. That same year, John Fraser, English nurseryman and later botanical collector to the Czar of Russia, brought D. coccinea seeds from Paris to the Apothecaries Gardens in England, where they flowered in his greenhouse a year later, providing Botanical Magazine with an illustration.In 1804, a new species, Dahlia sambucifolia, was successfully grown at Holland House, Kensington. Whilst in Madrid in 1804, Lady Holland was given either dahlia seeds or tubers by Cavanilles. She sent them back to England, to Lord Holland's librarian Mr Buonaiuti at Holland House, who successfully raised the plants. A year later, Buonaiuti produced two double flowers. The plants raised in 1804 did not survive; new stock was brought from France in 1815. In 1824, Lord Holland sent his wife a note containing the following verse:
"The dahlia you brought to our isle
Your praises for ever shall speak;
Mid gardens as sweet as your smile,
And in colour as bright as your cheek."
In 1805, German naturalist Alexander von Humboldt sent more seeds from Mexico to Aiton in England, Thouin in Paris, and Christoph Friedrich Otto, director of the Berlin Botanical Garden. More significantly, he sent seeds to botanist Carl Ludwig Willdenow in Germany. Willdenow now reclassified the rapidly growing number of species, changing the genus from Dahlia to Georgina; after naturalist Johann Gottlieb Georgi. He combined the Cavanilles species D. pinnata and D. rosea under the name of Georgina variabilis; D. coccinea was still held to be a separate species, which he renamed Georgina coccinea.
CLASSIFICATION
Since 1789 when Cavanilles first flowered the dahlia in Europe, there has been an ongoing effort by many growers, botanists and taxonomists, to determine the development of the dahlia to modern times. At least 85 species have been reported: approximately 25 of these were first reported from the wild, the remainder appeared in gardens in Europe. They were considered hybrids, the results of crossing between previously reported species, or developed from the seeds sent by Humboldt from Mexico in 1805, or perhaps from some other undocumented seeds that had found their way to Europe. Several of these were soon discovered to be identical with earlier reported species, but the greatest number are new varieties. Morphological variation is highly pronounced in the dahlia. William John Cooper Lawrence, who hybridized hundreds of families of dahlias in the 1920s, stated: "I have not yet seen any two plants in the families I have raised which were not to be distinguished one from the other. Constant reclassification of the 85 reported species has resulted in a considerably smaller number of distinct species, as there is a great deal of disagreement today between systematists over classification.
In 1829, all species growing in Europe were reclassified under an all-encompassing name of D. variabilis, Desf., though this is not an accepted name. Through the interspecies cross of the Humboldt seeds and the Cavanilles species, 22 new species were reported by that year, all of which had been classified in different ways by several different taxonomists, creating considerable confusion as to which species was which.
In 1830 William Smith suggested that all dahlia species could be divided into two groups for color, red-tinged and purple-tinged. In investigating this idea Lawrence determined that with the exception of D. variabilis, all dahlia species may be assigned to one of two groups for flower-colour: Group I (ivory-magenta) or Group II (yellow-orange-scarlet).
CIRCUMSCRIPTION
The genus Dahlia is situated in the Asteroideae subfamily of the Asteraceae, in the Coreopsideae tribe. Within that tribe it is the second largest genus, after Coreopsis, and appears as a well defined clade within the Coreopsideae.
SUBDIVISION
INFRAGENERIC SUBDIVISION
Sherff (1955), in the first modern taxonomy described three sections for the 18 species he recognised, Pseudodendron, Epiphytum and Dahlia. By 1969 Sørensen recognised 29 species and four sections by splitting off Entemophyllon from section Dahlia. By contrast Giannasi (1975) using a phytochemical analysis based on flavonoids, reduced the genus to just two sections, Entemophyllon and Dahlia, the latter having three subsections, Pseudodendron, Dahlia, and Merckii. Sørensen then issued a further revision in 1980, incorporating subsection Merckii in his original section Dahlia. When he described two new species in the 1980s (Dahlia tubulata and D. congestifolia), he placed them within his existing sections. A further species, Dahlia sorensenii was added by Hansen and Hjerting in (1996). At the same time they demonstrated that Dahlia pinnata should more properly be designated D. x pinnata. D. x pinnata was shown to actually be a variant of D. sorensenii that had acquired hybrid qualities before it was introduced to Europe in the sixteenth century and formally named by Cavanilles. The original wild D. pinnata is presumed extinct. Further species continue to be described, Saar (2003) describing 35 species. However separation of the sections on morphological, cytologal and biocemical criteria has not been entirely satisfactory.
To date these sectional divisions have not been fully supported phylogenetically, which demonstrate only section Entemophyllon as a distinct sectional clade. The other major grouping is the Core Dahlia Clade (CDC), which includes most of section Dahlia. The remainder of the species occupy what has been described as the Variable Root Clade (VRC) which includes the small section Pseudodendron but also the monotypic section Epiphytum and a number of species from within section Dahlia. Outside of these three clades lie D. tubulata and D. merckii as a polytomy.
Horticulturally the sections retain some usage, section Pseudodendron being referred to as 'Tree Dahlias', Epiphytum as the 'Vine Dahlia'. The remaining two herbaceous sections being distinguished by their pinnules, opposing (Dahlia) or alternating (Entemophyllon).
SECTIONS
Sections (including chromosome numbers), with geographical distribution;
- Epiphytum Sherff (2n = 32)
10 m tall climber with aerial roots 5 cm thick and up to more than 20 m long; pinnules opposite
1 species, D. macdougallii Sherff
Mexico: Oaxaca
- Entemophyllon P. D. Sorensen (2n = 34)
6 species
Mexico: Hidalgo, Nuevo León, Tamaulipas, Querétaro, Durango, San Luis Potosí
- Pseudodendron P. D. Sorensen (2n = 32)
3 species + D. excelsa of uncertain identity
Mexico: Chiapas, Guerrero, Jalisco, Michoacan, Oaxaca, and
Costa Rica, El Salvador, Guatemala & Colombia
- Dahlia (2n = 32, 36 or 64)
24 species
Mexico: Distrito Federal, Guerrero, Hidalgo, Morelos, Nuevo León, Puebla, San Luis Potosí, Tamaulipas, Veracruz, Oaxaca, Puebla, Chiapas, México, Huehuetenango, Chihuahua, Durango, Michoacan & Guatemala
Only Pseudodendron (D. imperialis) and Dahlia (D. australis, D. coccinea) occur outside Mexico.
SPECIES
There are currently 42 accepted species in the Dahlia genus, but new species continue to be described.
ETYMOLOGY
The naming of the plant itself has long been a subject of some confusion. Many sources state that the name "Dahlia" was bestowed by the pioneering Swedish botanist and taxonomist Carl Linnaeus to honor his late student, Anders Dahl, author of Observationes Botanicae. However, Linnaeus died in 1778, more than eleven years before the plant was introduced into Europe in 1789, so while it is generally agreed that the plant was named in 1791 in honor of Dahl, who had died two years before, Linnaeus could not have been the one who did so. It was probably Abbe Antonio Jose Cavanilles, Director of the Royal Gardens of Madrid, who should be credited with the attempt to scientifically define the genus, since he not only received the first specimens from Mexico in 1789, but named the first three species that flowered from the cuttings.
Regardless of who bestowed it, the name was not so easily established. In 1805, German botanist Carl Ludwig Willdenow, asserting that the genus Dahlia Thunb. (published a year after Cavanilles's genus and now considered a synonym of Trichocladus) was more widely accepted, changed the plants' genus from Dahlia to Georgina; after the German-born naturalist Johann Gottlieb Georgi, a professor at the Imperial Academy of Sciences of St. Petersburg, Russia. He also reclassified and renamed the first three species grown, and identified, by Cavanilles. It was not until 1810, in a published article, that he officially adopted the Cavanilles' original designation of Dahlia. However, the name Georgina still persisted in Germany for the next few decades.
"Dahl" is a homophone of the Swedish word "dal", or "valley"; although it is not a true translation, the plant is sometimes referred to as the "valley flower".
DISTRIBUTION AND HABITAT
Predominantly Mexico, but some species are found ranging as far south as northern South America. D. australis occurs at least as far south as southwestern Guatemala, while D. coccinea and D. imperialis also occur in parts of Central America and northern South America. Dahlia is a genus of the uplands and mountains, being found at elevations between 1,500 and 3,700 meters, in what has been described as a "pine-oak woodland" vegetative zone. Most species have limited ranges scattered throughout many mountain ranges in Mexico.
ECOLOGY
The commonest pollinators are bees and small beetles.
PESTS AND DISEASES
Slugs and snails are serious pests in some parts of the world, particularly in spring when new growth is emerging through the soil. Earwigs can also disfigure the blooms. The other main pests likely to be encountered are aphids (usually on young stems and immature flower buds), red spider mite (causing foliage mottling and discolouration, worse in hot and dry conditions) and capsid bugs (resulting in contortion and holes at growing tips). Diseases affecting dahlias include powdery mildew, grey mould (Botrytis cinerea), verticillium wilt, dahlia smut (Entyloma calendulae f. dahliae), phytophthora and some plant viruses. Dahlias are a source of food for the larvae of some Lepidoptera species including Angle Shades, Common Swift, Ghost Moth and Large Yellow Underwing.
CULTIVATION
Dahlias grow naturally in climates which do not experience frost (the tubers are hardy to USDA Zone 8), consequently they are not adapted to withstand sub-zero temperatures. However, their tuberous nature enables them to survive periods of dormancy, and this characteristic means that gardeners in temperate climates with frosts can grow dahlias successfully, provided the tubers are lifted from the ground and stored in cool yet frost-free conditions during the winter. Planting the tubers quite deep (10 – 15 cm) also provides some protection. When in active growth, modern dahlia hybrids perform most successfully in well-watered yet free-draining soils, in situations receiving plenty of sunlight. Taller cultivars usually require some form of staking as they grow, and all garden dahlias need deadheading regularly, once flowering commences.
HORTICURAL CLASSIFICATION
HISTORY
The inappropriate term D. variabilis is often used to describe the cultivars of Dahlia since the correct parentage remains obscure, but probably involves Dahlia coccinea. In 1846 the Caledonia Horticultural Society of Edinburgh offered a prize of 2,000 pounds to the first person succeeding in producing a blue dahlia. This has to date not been accomplished. While dahlias produce anthocyanin, an element necessary for the production of the blue, to achieve a true blue color in a plant, the anthocyanin delphinidin needs six hydroxyl groups. To date dahlias have only developed five, so the closest that breeders have come to achieving a "blue" specimen are variations of mauve, purples and lilac hues.
By the beginning of the twentieth century a number of different types were recognised. These terms were based on shape or colour, and the National Dahlia Society included cactus, pompon, single, show and fancy in its 1904 guide. Many national societies developed their own classification systems until 1962 when the International Horticultural Congress agreed to develop an internationally recognised system at it Brussels meeting that year, and subsequently in Maryland in 1966. This culminated in the 1969 publication of The International Register of Dahlia Names by the Royal Horticultural Society which became the central registering authority.
This system depended primarily on the visibility of the central disc, whether it was open centred or whether only ray florets were apparent centrally (double bloom). The double bloom cultivars were then subdivided according to the way in which they were folded along their longitudinal axis, flat, involute (curled inwards) or revolute (curling backwards). If the end of the ray floret was split, they were considered fimbriated. Based on these characteristics, nine groups were defined plua a tenth miscellaneous group for any cultivars not fitting the above characteristics. Fimbriated dahlias were added in 2004, and two further groups (Single and Double orchid) in 2007. The last group to be added, Peony, first appeared in 2012.
In many cases the bloom diametre was then used to further label certain groups from miniature through to giant. This practice was abandoned in 2012.
MODERN SYSTEM (RHS)
There are now more than 57,000 registered cultivars, which are officially registered through the Royal Horticultural Society (RHS). The official register is The International Register of Dahlia Names 1969 (1995 reprint) which is updated by annual supplements. The original 1969 registry published about 14,000 cultivars adding a further 1700 by 1986 and in 2003 there were 18,000. Since then about a hundred new cultivars are added annually.
FLOWER TYPE
The official RHS classification lists fourteen groups, grouped by flower type, together with the abbreviations used by the RHS;
Group 1 – Single-flowered dahlias (Sin) — Flower has a central disc with a single outer ring of florets (which may overlap) encircling it, and which may be rounded or pointed.
Group 2 – Anemone-flowered dahlias (Anem) — The centre of the flower consists of dense elongated tubular florets, longer than the disc florets of Single dahlias, while the outer parts have one or more rings of flatter ray florets. Disc absent.
Group 3 – Collerette dahlias (Col) — Large flat florets forming a single outer ring around a central disc and which may overlap a smaller circle of florets closer to the centre, which have the appearance of a collar.
Group 4 – Waterlily dahlias (WL) — Double blooms, broad sparse curved, slightly curved or flat florets and very shallow in depth compared with other dahlias. Depth less than half the diameter of the bloom. Group 5 – Decorative dahlias (D) — Double blooms, ray florets broad, flat, involute no more than seventy five per cent of the longitudinal axis, slightly twisted and usually bluntly pointed. No visible central disc.
Group 6 – Ball dahlias (Ba)— Double blooms that are ball shaped or slightly flattened. Ray florets blunt or rounded at the tips, margins arranged spirally, involute for at least seventy five percent of the length of the florets. Larger than Pompons.
Group 7 – Pompon dahlias (Pom) — Double spherical miniature flowers made up entirely from florets that are curved inwards (involute) for their entire length (longitudinal axis), resembling a pompon.
Group 8 – Cactus dahlias (C) — Double blooms, ray florets pointed, with majority revolute (rolled) over more than fifty percent of their longitudinal axis, and straight or incurved. Narrower than Semi cactus.
Group 9 – Semi cactus dahlias (S–c)— Double blooms, very pointed ray florets, revolute for greater than twenty five percent and less than fifty percent of their longitudinal axis. Broad at the base and straight or incurved, almost spiky in appearance.
Group 10 – Miscellaneous dahlias (Misc) — not described in any other group.
Group 11 – Fimbriated dahlias (Fim) — ray florets evenly split or notched into two or more divisions, uniformly throughout the bloom, creating a fimbriated (fringed) effect. The petals may be flat, involute, revolute, straight, incurving or twisted.
Group 12 – Single Orchid (Star) dahlias (SinO) — single outer ring of florets surround a central disc. The ray florets are either involute or revolute.
Group 13 – Double Orchid dahlias (DblO) — Double blooms with triangular centres. The ray florets are narrowly lanceolate and are either involute or revolute. The central disc is absent.
Group 14 – Peony-flowered dahlias (P) — Large flowers with three or four rows of rays that are flattened and expanded and arranged irregularly. The rays surround a golden disc similar to that of Single dahlias.
FLOWER SIZE
Earlier versions of the registry subdivided some groups by flower size. Groups 4, 5, 8 and 9 were divided into five subgroups (A to E) from Giant to Miniature, and Group 6 into two subgroups, Small and Miniature. Dahlias were then described by Group and Subgroup, e.g. 5(d) ‘Ace Summer Sunset’. Some Dahlia Societies have continued this practice, but this is neither official nor standardised. As of 2013 The RHS uses two size descriptors
Dwarf Bedder (Dw.B.) — not usually exceeding 600 mm in height, e.g. 'Preston Park' (Sin/DwB)
Lilliput dahlias (Lil) — not usually exceeding 300 mm in height, with single, semi-double or double florets up to 26 mm in diameter. ("baby" or "top-mix" dahlias), e.g. 'Harvest Tiny Tot' (Misc/Lil)
Sizes can range from tiny micro dahlias with flowers less than 50mm to giants that are over 250mm in diameter. The groupings listed here are from the New Zealand Society.
Giant flowered cultivars have blooms with a diameter of over 250mm.
Large flowered cultivars have blooms with a diameter between 200mm-250mm.
Medium flowered cultivars have blooms with a diameter between 155mm-200mm.
Small flowered cultivars have blooms with a diameter between 115mm-155mm.
Miniature flowered cultivars have blooms with a diameter between 50mm-115mm.
Pompom flowered cultivars have blooms with a diameter less than 50mm.
In addition to the official classification and the terminology used by various dahlia societies, individual horticulturalists use a wide range of other descriptions, such as 'Incurved' and abbreviations in their catalogues, such as CO for Collarette.
BRANDING
Some plant growers include their brand name in the cultivar name. Thus Fides (part of the Dümmen Orange Group) in the Netherlands developed a series of cultivars which they named the Dahlinova Series, for example Dahlinova 'Carolina Burgundy'. These are Group 10 Miscellaneous in the RHS classification scheme.
DOUBLE DAHLIAS
In 1805, several new species were reported with red, purple, lilac, and pale yellow coloring, and the first true double flower was produced in Belgium. One of the more popular concepts of dahlia history, and the basis for many different interpretations and confusion, is that all the original discoveries were single flowered types, which, through hybridization and selective breeding, produced double forms. Many of the species of dahlias then, and now, have single flowered blooms. coccinea, the third dahlia to bloom in Europe, was a single. But two of the three drawings of dahlias by Dominguez, made in Mexico between 1570–77, showed definite characteristics of doubling. In the early days of the dahlia in Europe, the word "double" simply designated flowers with more than one row of petals. The greatest effort was now directed to developing improved types of double dahlias.
During the years 1805 to 1810 several people claimed to have produced a double dahlia. In 1805 Henry C. Andrews made a drawing of such a plant in the collection of Lady Holland, grown from seedlings sent that year from Madrid. Like other doubles of the time it did not resemble the doubles of today. The first modern double, or full double, appeared in Belgium; M. Donckelaar, Director of the Botanic Garden at Louvain, selected plants for that characteristic, and within a few years secured three fully double forms. By 1826 double varieties were being grown almost exclusively, and there was very little interest in the single forms. Up to this time all the so-called double dahlias had been purple, or tinged with purple, and it was doubted if a variety untinged with that color was obtainable.
In 1843, scented single forms of dahlias were first reported in Neu Verbass, Austria. D. crocea, a fragrant variety grown from one of the Humboldt seeds, was probably interbred with the single D. coccinea. A new scented species would not be introduced until the next century when the D. coronata was brought from Mexico to Germany in 1907.
The exact date the dahlia was introduced in the United States is uncertain. One of the first Dahlias in the USA may be the D. coccinea speciosissima grown by Mr William Leathe, of Cambridgeport, near Boston, around 1929. According to Edward Sayers "it attracted much admiration, and at that time was considered a very elegant flower, it was however soon eclipsed by that splendid scarlet, the Countess of Liverpool". However 9 cultivars were already listed in the catalog from Thornburn, 1825. And even earlier reference can be found in a catalogue from the Linnaean Botanical Garden, New York, 1820, that includes one scarlet, one purple, and two double orange Dahlias for sale.
Sayers stated that "No person has done more for the introduction and advancement of the culture of the Dahlia than George C. Thorburn, of New York, who yearly flowers many thousand plants at his place at Hallet's Cove, near Harlaem. The show there in the flowering season is a rich treat for the lovers of floriculture : for almost every variety can be seen growing in two large blocks or masses which lead from the road to the dwelling-house, and form a complete field of the Dahlia as a foreground to the house. Mr T. Hogg, Mr William Read, and many other well known florists, have also contributed much in the vicinity of New York, to the introduction of the Dahlia. Indeed so general has become the taste that almost every garden has its show of the Dahlia in the season." In Boston too there were many collections, a collection from the Messrs Hovey of Cambridgeport was also mentioned.
In 1835 Thomas Bridgeman, published a list of 160 double dahlias in his Florist's Guide. 60 of the choicest were supplied by Mr. G. C. Thornburn of Astoria, N.Y. who got most of them from contacts in the UK. Not a few of them had taken prices "at the English and American exhibitions".
"STARS OF DEVIL"
In 1872 J.T. van der Berg of Utrecht in the Netherlands, received a shipment of seeds and plants from a friend in Mexico. The entire shipment was badly rotted and appeared to be ruined, but van der Berg examined it carefully and found a small piece of root that seemed alive. He planted and carefully tended it; it grew into a plant that he identified as a dahlia. He made cuttings from the plant during the winter of 1872-1873. This was an entirely different type of flower, with a rich, red color and a high degree of doubling. In 1874 van der Berg catalogued it for sale, calling it Dahlia juarezii to honor Mexican President Benito Pablo Juarez, who had died the year before, and described it as "...equal to the beautiful color of the red poppy. Its form is very outstanding and different in every respect of all known dahlia flowers.".
This plant has perhaps had a greater influence on the popularity of the modern dahlia than any other. Called "Les Etoiles de Diable" (Stars of the Devil) in France and "Cactus dahlia" elsewhere, the edges of its petals rolled backwards, rather than forward, and this new form revolutionized the dahlia world. It was thought to be a distinct mutation since no other plant that resembled it could be found in the wild. Today it is assumed that D. juarezii had, at one time, existed in Mexico and subsequently disappeared. Nurserymen in Europe crossbred this plant with dahlias discovered earlier; the results became the progenitors of all modern dahlia hybrids today.
AWARD OF GARDEN MERIT (RHS)
As of 2015, 124 dahlia cultivars have gained the Royal Horticultural Society's Award of Garden Merit:
"Bednall beauty"
"Bishop of Llandaff"
"Clair de lune"
"David Howard"
"Ellen Huston"
"Fascination"
"Gallery art deco"
"Gallery Art Nouveau"
"Glorie van Heemstede"
"Honka"
"Moonfire"
"Twyning's After Eight"
USES
FLORICULTURE
The asterid eudicots contain two economically important geophyte genera, Dahlia and Liatris. Horticulturally the garden dahlia is usually treated as the cultigen D. variabilis Hort., which while being responsible for thousands of cultivars has an obscure taxonomic status.
OTHER
Today the dahlia is still considered one of the native ingredients in Oaxacan cuisine; several cultivars are still grown especially for their large, sweet potato-like tubers. Dacopa, an intense mocha-tasting extract from the roasted tubers, is used to flavor beverages throughout Central America.
In Europe and America, prior to the discovery of insulin in 1923, diabetics - as well as consumptives - were often given a substance called Atlantic starch or diabetic sugar, derived from inulin, a naturally occurring form of fruit sugar, extracted from dahlia tubers. Inulin is still used in clinical tests for kidney functionality.
WIKIPEDIA
Dahlia (UK /deɪliə/ or US /dɑːliə/) is a genus of bushy, tuberous, herbaceous perennial plants native to Mexico. A member of the Asteraceae (or Compositae), dicotyledonous plants, related species include the sunflower, daisy, chrysanthemum, and zinnia. There are 42 species of dahlia, with hybrids commonly grown as garden plants. Flower forms are variable, with one head per stem; these can be as small as 5.1 cm diameter or up to 30 cm ("dinner plate"). This great variety results from dahlias being octoploids—that is, they have eight sets of homologous chromosomes, whereas most plants have only two. In addition, dahlias also contain many transposons - genetic pieces that move from place to place upon an allele - which contributes to their manifesting such great diversity.
The stems are leafy, ranging in height from as low as 30 cm to more than 1.8–2.4 m. The majority of species do not produce scented flowers or cultivars. Like most plants that do not attract pollinating insects through scent, they are brightly colored, displaying most hues, with the exception of blue.
The dahlia was declared the national flower of Mexico in 1963. The tubers were grown as a food crop by the Aztecs, but this use largely died out after the Spanish Conquest. Attempts to introduce the tubers as a food crop in Europe were unsuccessful.
DESCRIPTION
Perennial plants, with mostly tuberous roots. While some have herbaceous stems, others have stems which lignify in the absence of secondary tissue and resprout following winter dormancy, allowing further seasons of growth. as a member of the Asteraceae the flower head is actually a composite (hence the older name Compositae) with both central disc florets and surrounding ray florets. Each floret is a flower in its own right, but is often incorrectly described as a petal, particularly by horticulturalists. The modern mame Asteraceae refers to the appearance of a star with surrounding rays.
TAXONOMY
HISTORY
EARLY HISTORY
Spaniards reported finding the plants growing in Mexico in 1525, but the earliest known description is by Francisco Hernández, physician to Philip II, who was ordered to visit Mexico in 1570 to study the "natural products of that country". They were used as a source of food by the indigenous peoples, and were both gathered in the wild and cultivated. The Aztecs used them to treat epilepsy, and employed the long hollow stem of the (Dahlia imperalis) for water pipes. The indigenous peoples variously identified the plants as "Chichipatl" (Toltecs) and "Acocotle" or "Cocoxochitl" (Aztecs). From Hernandez' perception of Aztec, to Spanish, through various other translations, the word is "water cane", "water pipe", "water pipe flower", "hollow stem flower" and "cane flower". All these refer to the hollowness of the plants' stem.Hernandez described two varieties of dahlias (the pinwheel-like Dahlia pinnata and the huge Dahlia imperialis) as well as other medicinal plants of New Spain. Francisco Dominguez, a Hidalgo gentleman who accompanied Hernandez on part of his seven-year study, made a series of drawings to supplement the four volume report. Three of his drawings showed plants with flowers: two resembled the modern bedding dahlia, and one resembled the species Dahlia merki; all displayed a high degree of doubleness. In 1578 the manuscript, entitled Nova Plantarum, Animalium et Mineralium Mexicanorum Historia, was sent back to the Escorial in Madrid; they were not translated into Latin by Francisco Ximenes until 1615. In 1640, Francisco Cesi, President of the Academia Linei of Rome, bought the Ximenes translation, and after annotating it, published it in 1649-1651 in two volumes as Rerum Medicarum Novae Hispaniae Thesaurus Seu Nova Plantarium, Animalium et Mineraliuím Mexicanorum Historia. The original manuscripts were destroyed in a fire in the mid-1600s.
EUROPEAN INTRODUCTION
In 1787, the French botanist Nicolas-Joseph Thiéry de Menonville, sent to Mexico to steal the cochineal insect valued for its scarlet dye, reported the strangely beautiful flowers he had seen growing in a garden in Oaxaca. In 1789, Vicente Cervantes, Director of the Botanical Garden at Mexico City, sent "plant parts" to Abbe Antonio José Cavanilles, Director of the Royal Gardens of Madrid. Cavanilles flowered one plant that same year, then the second one a year later. In 1791 he called the new growths "Dahlia" for Anders Dahl. The first plant was called Dahlia pinnata after its pinnate foliage; the second, Dahlia rosea for its rose-purple color. In 1796 Cavanilles flowered a third plant from the parts sent by Cervantes, which he named Dahlia coccinea for its scarlet color.In 1798, Cavanilles sent D. Pinnata seeds to Parma, Italy. That year, the Marchioness of Bute, wife of The Earl of Bute, the English Ambassador to Spain, obtained a few seeds from Cavanilles and sent them to Kew Gardens, where they flowered but were lost after two to three years. In the following years Madrid sent seeds to Berlin and Dresden in Germany, and to Turin and Thiene in Italy. In 1802, Cavanilles sent tubers of "these three" (D. pinnata, D. rosea, D. coccinea) to Swiss botanist Augustin Pyramus de Candolle at University of Montpelier in France, Andre Thouin at the Jardin des Plantes in Paris and Scottish botanist William Aiton at Kew Gardens. That same year, John Fraser, English nurseryman and later botanical collector to the Czar of Russia, brought D. coccinea seeds from Paris to the Apothecaries Gardens in England, where they flowered in his greenhouse a year later, providing Botanical Magazine with an illustration.In 1804, a new species, Dahlia sambucifolia, was successfully grown at Holland House, Kensington. Whilst in Madrid in 1804, Lady Holland was given either dahlia seeds or tubers by Cavanilles. She sent them back to England, to Lord Holland's librarian Mr Buonaiuti at Holland House, who successfully raised the plants. A year later, Buonaiuti produced two double flowers. The plants raised in 1804 did not survive; new stock was brought from France in 1815. In 1824, Lord Holland sent his wife a note containing the following verse:
"The dahlia you brought to our isle
Your praises for ever shall speak;
Mid gardens as sweet as your smile,
And in colour as bright as your cheek."
In 1805, German naturalist Alexander von Humboldt sent more seeds from Mexico to Aiton in England, Thouin in Paris, and Christoph Friedrich Otto, director of the Berlin Botanical Garden. More significantly, he sent seeds to botanist Carl Ludwig Willdenow in Germany. Willdenow now reclassified the rapidly growing number of species, changing the genus from Dahlia to Georgina; after naturalist Johann Gottlieb Georgi. He combined the Cavanilles species D. pinnata and D. rosea under the name of Georgina variabilis; D. coccinea was still held to be a separate species, which he renamed Georgina coccinea.
CLASSIFICATION
Since 1789 when Cavanilles first flowered the dahlia in Europe, there has been an ongoing effort by many growers, botanists and taxonomists, to determine the development of the dahlia to modern times. At least 85 species have been reported: approximately 25 of these were first reported from the wild, the remainder appeared in gardens in Europe. They were considered hybrids, the results of crossing between previously reported species, or developed from the seeds sent by Humboldt from Mexico in 1805, or perhaps from some other undocumented seeds that had found their way to Europe. Several of these were soon discovered to be identical with earlier reported species, but the greatest number are new varieties. Morphological variation is highly pronounced in the dahlia. William John Cooper Lawrence, who hybridized hundreds of families of dahlias in the 1920s, stated: "I have not yet seen any two plants in the families I have raised which were not to be distinguished one from the other. Constant reclassification of the 85 reported species has resulted in a considerably smaller number of distinct species, as there is a great deal of disagreement today between systematists over classification.
In 1829, all species growing in Europe were reclassified under an all-encompassing name of D. variabilis, Desf., though this is not an accepted name. Through the interspecies cross of the Humboldt seeds and the Cavanilles species, 22 new species were reported by that year, all of which had been classified in different ways by several different taxonomists, creating considerable confusion as to which species was which.
In 1830 William Smith suggested that all dahlia species could be divided into two groups for color, red-tinged and purple-tinged. In investigating this idea Lawrence determined that with the exception of D. variabilis, all dahlia species may be assigned to one of two groups for flower-colour: Group I (ivory-magenta) or Group II (yellow-orange-scarlet).
CIRCUMSCRIPTION
The genus Dahlia is situated in the Asteroideae subfamily of the Asteraceae, in the Coreopsideae tribe. Within that tribe it is the second largest genus, after Coreopsis, and appears as a well defined clade within the Coreopsideae.
SUBDIVISION
INFRAGENERIC SUBDIVISION
Sherff (1955), in the first modern taxonomy described three sections for the 18 species he recognised, Pseudodendron, Epiphytum and Dahlia. By 1969 Sørensen recognised 29 species and four sections by splitting off Entemophyllon from section Dahlia. By contrast Giannasi (1975) using a phytochemical analysis based on flavonoids, reduced the genus to just two sections, Entemophyllon and Dahlia, the latter having three subsections, Pseudodendron, Dahlia, and Merckii. Sørensen then issued a further revision in 1980, incorporating subsection Merckii in his original section Dahlia. When he described two new species in the 1980s (Dahlia tubulata and D. congestifolia), he placed them within his existing sections. A further species, Dahlia sorensenii was added by Hansen and Hjerting in (1996). At the same time they demonstrated that Dahlia pinnata should more properly be designated D. x pinnata. D. x pinnata was shown to actually be a variant of D. sorensenii that had acquired hybrid qualities before it was introduced to Europe in the sixteenth century and formally named by Cavanilles. The original wild D. pinnata is presumed extinct. Further species continue to be described, Saar (2003) describing 35 species. However separation of the sections on morphological, cytologal and biocemical criteria has not been entirely satisfactory.
To date these sectional divisions have not been fully supported phylogenetically, which demonstrate only section Entemophyllon as a distinct sectional clade. The other major grouping is the Core Dahlia Clade (CDC), which includes most of section Dahlia. The remainder of the species occupy what has been described as the Variable Root Clade (VRC) which includes the small section Pseudodendron but also the monotypic section Epiphytum and a number of species from within section Dahlia. Outside of these three clades lie D. tubulata and D. merckii as a polytomy.
Horticulturally the sections retain some usage, section Pseudodendron being referred to as 'Tree Dahlias', Epiphytum as the 'Vine Dahlia'. The remaining two herbaceous sections being distinguished by their pinnules, opposing (Dahlia) or alternating (Entemophyllon).
SECTIONS
Sections (including chromosome numbers), with geographical distribution;
- Epiphytum Sherff (2n = 32)
10 m tall climber with aerial roots 5 cm thick and up to more than 20 m long; pinnules opposite
1 species, D. macdougallii Sherff
Mexico: Oaxaca
- Entemophyllon P. D. Sorensen (2n = 34)
6 species
Mexico: Hidalgo, Nuevo León, Tamaulipas, Querétaro, Durango, San Luis Potosí
- Pseudodendron P. D. Sorensen (2n = 32)
3 species + D. excelsa of uncertain identity
Mexico: Chiapas, Guerrero, Jalisco, Michoacan, Oaxaca, and
Costa Rica, El Salvador, Guatemala & Colombia
- Dahlia (2n = 32, 36 or 64)
24 species
Mexico: Distrito Federal, Guerrero, Hidalgo, Morelos, Nuevo León, Puebla, San Luis Potosí, Tamaulipas, Veracruz, Oaxaca, Puebla, Chiapas, México, Huehuetenango, Chihuahua, Durango, Michoacan & Guatemala
Only Pseudodendron (D. imperialis) and Dahlia (D. australis, D. coccinea) occur outside Mexico.
SPECIES
There are currently 42 accepted species in the Dahlia genus, but new species continue to be described.
ETYMOLOGY
The naming of the plant itself has long been a subject of some confusion. Many sources state that the name "Dahlia" was bestowed by the pioneering Swedish botanist and taxonomist Carl Linnaeus to honor his late student, Anders Dahl, author of Observationes Botanicae. However, Linnaeus died in 1778, more than eleven years before the plant was introduced into Europe in 1789, so while it is generally agreed that the plant was named in 1791 in honor of Dahl, who had died two years before, Linnaeus could not have been the one who did so. It was probably Abbe Antonio Jose Cavanilles, Director of the Royal Gardens of Madrid, who should be credited with the attempt to scientifically define the genus, since he not only received the first specimens from Mexico in 1789, but named the first three species that flowered from the cuttings.
Regardless of who bestowed it, the name was not so easily established. In 1805, German botanist Carl Ludwig Willdenow, asserting that the genus Dahlia Thunb. (published a year after Cavanilles's genus and now considered a synonym of Trichocladus) was more widely accepted, changed the plants' genus from Dahlia to Georgina; after the German-born naturalist Johann Gottlieb Georgi, a professor at the Imperial Academy of Sciences of St. Petersburg, Russia. He also reclassified and renamed the first three species grown, and identified, by Cavanilles. It was not until 1810, in a published article, that he officially adopted the Cavanilles' original designation of Dahlia. However, the name Georgina still persisted in Germany for the next few decades.
"Dahl" is a homophone of the Swedish word "dal", or "valley"; although it is not a true translation, the plant is sometimes referred to as the "valley flower".
DISTRIBUTION AND HABITAT
Predominantly Mexico, but some species are found ranging as far south as northern South America. D. australis occurs at least as far south as southwestern Guatemala, while D. coccinea and D. imperialis also occur in parts of Central America and northern South America. Dahlia is a genus of the uplands and mountains, being found at elevations between 1,500 and 3,700 meters, in what has been described as a "pine-oak woodland" vegetative zone. Most species have limited ranges scattered throughout many mountain ranges in Mexico.
ECOLOGY
The commonest pollinators are bees and small beetles.
PESTS AND DISEASES
Slugs and snails are serious pests in some parts of the world, particularly in spring when new growth is emerging through the soil. Earwigs can also disfigure the blooms. The other main pests likely to be encountered are aphids (usually on young stems and immature flower buds), red spider mite (causing foliage mottling and discolouration, worse in hot and dry conditions) and capsid bugs (resulting in contortion and holes at growing tips). Diseases affecting dahlias include powdery mildew, grey mould (Botrytis cinerea), verticillium wilt, dahlia smut (Entyloma calendulae f. dahliae), phytophthora and some plant viruses. Dahlias are a source of food for the larvae of some Lepidoptera species including Angle Shades, Common Swift, Ghost Moth and Large Yellow Underwing.
CULTIVATION
Dahlias grow naturally in climates which do not experience frost (the tubers are hardy to USDA Zone 8), consequently they are not adapted to withstand sub-zero temperatures. However, their tuberous nature enables them to survive periods of dormancy, and this characteristic means that gardeners in temperate climates with frosts can grow dahlias successfully, provided the tubers are lifted from the ground and stored in cool yet frost-free conditions during the winter. Planting the tubers quite deep (10 – 15 cm) also provides some protection. When in active growth, modern dahlia hybrids perform most successfully in well-watered yet free-draining soils, in situations receiving plenty of sunlight. Taller cultivars usually require some form of staking as they grow, and all garden dahlias need deadheading regularly, once flowering commences.
HORTICURAL CLASSIFICATION
HISTORY
The inappropriate term D. variabilis is often used to describe the cultivars of Dahlia since the correct parentage remains obscure, but probably involves Dahlia coccinea. In 1846 the Caledonia Horticultural Society of Edinburgh offered a prize of 2,000 pounds to the first person succeeding in producing a blue dahlia. This has to date not been accomplished. While dahlias produce anthocyanin, an element necessary for the production of the blue, to achieve a true blue color in a plant, the anthocyanin delphinidin needs six hydroxyl groups. To date dahlias have only developed five, so the closest that breeders have come to achieving a "blue" specimen are variations of mauve, purples and lilac hues.
By the beginning of the twentieth century a number of different types were recognised. These terms were based on shape or colour, and the National Dahlia Society included cactus, pompon, single, show and fancy in its 1904 guide. Many national societies developed their own classification systems until 1962 when the International Horticultural Congress agreed to develop an internationally recognised system at it Brussels meeting that year, and subsequently in Maryland in 1966. This culminated in the 1969 publication of The International Register of Dahlia Names by the Royal Horticultural Society which became the central registering authority.
This system depended primarily on the visibility of the central disc, whether it was open centred or whether only ray florets were apparent centrally (double bloom). The double bloom cultivars were then subdivided according to the way in which they were folded along their longitudinal axis, flat, involute (curled inwards) or revolute (curling backwards). If the end of the ray floret was split, they were considered fimbriated. Based on these characteristics, nine groups were defined plua a tenth miscellaneous group for any cultivars not fitting the above characteristics. Fimbriated dahlias were added in 2004, and two further groups (Single and Double orchid) in 2007. The last group to be added, Peony, first appeared in 2012.
In many cases the bloom diametre was then used to further label certain groups from miniature through to giant. This practice was abandoned in 2012.
MODERN SYSTEM (RHS)
There are now more than 57,000 registered cultivars, which are officially registered through the Royal Horticultural Society (RHS). The official register is The International Register of Dahlia Names 1969 (1995 reprint) which is updated by annual supplements. The original 1969 registry published about 14,000 cultivars adding a further 1700 by 1986 and in 2003 there were 18,000. Since then about a hundred new cultivars are added annually.
FLOWER TYPE
The official RHS classification lists fourteen groups, grouped by flower type, together with the abbreviations used by the RHS;
Group 1 – Single-flowered dahlias (Sin) — Flower has a central disc with a single outer ring of florets (which may overlap) encircling it, and which may be rounded or pointed.
Group 2 – Anemone-flowered dahlias (Anem) — The centre of the flower consists of dense elongated tubular florets, longer than the disc florets of Single dahlias, while the outer parts have one or more rings of flatter ray florets. Disc absent.
Group 3 – Collerette dahlias (Col) — Large flat florets forming a single outer ring around a central disc and which may overlap a smaller circle of florets closer to the centre, which have the appearance of a collar.
Group 4 – Waterlily dahlias (WL) — Double blooms, broad sparse curved, slightly curved or flat florets and very shallow in depth compared with other dahlias. Depth less than half the diameter of the bloom. Group 5 – Decorative dahlias (D) — Double blooms, ray florets broad, flat, involute no more than seventy five per cent of the longitudinal axis, slightly twisted and usually bluntly pointed. No visible central disc.
Group 6 – Ball dahlias (Ba)— Double blooms that are ball shaped or slightly flattened. Ray florets blunt or rounded at the tips, margins arranged spirally, involute for at least seventy five percent of the length of the florets. Larger than Pompons.
Group 7 – Pompon dahlias (Pom) — Double spherical miniature flowers made up entirely from florets that are curved inwards (involute) for their entire length (longitudinal axis), resembling a pompon.
Group 8 – Cactus dahlias (C) — Double blooms, ray florets pointed, with majority revolute (rolled) over more than fifty percent of their longitudinal axis, and straight or incurved. Narrower than Semi cactus.
Group 9 – Semi cactus dahlias (S–c)— Double blooms, very pointed ray florets, revolute for greater than twenty five percent and less than fifty percent of their longitudinal axis. Broad at the base and straight or incurved, almost spiky in appearance.
Group 10 – Miscellaneous dahlias (Misc) — not described in any other group.
Group 11 – Fimbriated dahlias (Fim) — ray florets evenly split or notched into two or more divisions, uniformly throughout the bloom, creating a fimbriated (fringed) effect. The petals may be flat, involute, revolute, straight, incurving or twisted.
Group 12 – Single Orchid (Star) dahlias (SinO) — single outer ring of florets surround a central disc. The ray florets are either involute or revolute.
Group 13 – Double Orchid dahlias (DblO) — Double blooms with triangular centres. The ray florets are narrowly lanceolate and are either involute or revolute. The central disc is absent.
Group 14 – Peony-flowered dahlias (P) — Large flowers with three or four rows of rays that are flattened and expanded and arranged irregularly. The rays surround a golden disc similar to that of Single dahlias.
FLOWER SIZE
Earlier versions of the registry subdivided some groups by flower size. Groups 4, 5, 8 and 9 were divided into five subgroups (A to E) from Giant to Miniature, and Group 6 into two subgroups, Small and Miniature. Dahlias were then described by Group and Subgroup, e.g. 5(d) ‘Ace Summer Sunset’. Some Dahlia Societies have continued this practice, but this is neither official nor standardised. As of 2013 The RHS uses two size descriptors
Dwarf Bedder (Dw.B.) — not usually exceeding 600 mm in height, e.g. 'Preston Park' (Sin/DwB)
Lilliput dahlias (Lil) — not usually exceeding 300 mm in height, with single, semi-double or double florets up to 26 mm in diameter. ("baby" or "top-mix" dahlias), e.g. 'Harvest Tiny Tot' (Misc/Lil)
Sizes can range from tiny micro dahlias with flowers less than 50mm to giants that are over 250mm in diameter. The groupings listed here are from the New Zealand Society.
Giant flowered cultivars have blooms with a diameter of over 250mm.
Large flowered cultivars have blooms with a diameter between 200mm-250mm.
Medium flowered cultivars have blooms with a diameter between 155mm-200mm.
Small flowered cultivars have blooms with a diameter between 115mm-155mm.
Miniature flowered cultivars have blooms with a diameter between 50mm-115mm.
Pompom flowered cultivars have blooms with a diameter less than 50mm.
In addition to the official classification and the terminology used by various dahlia societies, individual horticulturalists use a wide range of other descriptions, such as 'Incurved' and abbreviations in their catalogues, such as CO for Collarette.
BRANDING
Some plant growers include their brand name in the cultivar name. Thus Fides (part of the Dümmen Orange Group) in the Netherlands developed a series of cultivars which they named the Dahlinova Series, for example Dahlinova 'Carolina Burgundy'. These are Group 10 Miscellaneous in the RHS classification scheme.
DOUBLE DAHLIAS
In 1805, several new species were reported with red, purple, lilac, and pale yellow coloring, and the first true double flower was produced in Belgium. One of the more popular concepts of dahlia history, and the basis for many different interpretations and confusion, is that all the original discoveries were single flowered types, which, through hybridization and selective breeding, produced double forms. Many of the species of dahlias then, and now, have single flowered blooms. coccinea, the third dahlia to bloom in Europe, was a single. But two of the three drawings of dahlias by Dominguez, made in Mexico between 1570–77, showed definite characteristics of doubling. In the early days of the dahlia in Europe, the word "double" simply designated flowers with more than one row of petals. The greatest effort was now directed to developing improved types of double dahlias.
During the years 1805 to 1810 several people claimed to have produced a double dahlia. In 1805 Henry C. Andrews made a drawing of such a plant in the collection of Lady Holland, grown from seedlings sent that year from Madrid. Like other doubles of the time it did not resemble the doubles of today. The first modern double, or full double, appeared in Belgium; M. Donckelaar, Director of the Botanic Garden at Louvain, selected plants for that characteristic, and within a few years secured three fully double forms. By 1826 double varieties were being grown almost exclusively, and there was very little interest in the single forms. Up to this time all the so-called double dahlias had been purple, or tinged with purple, and it was doubted if a variety untinged with that color was obtainable.
In 1843, scented single forms of dahlias were first reported in Neu Verbass, Austria. D. crocea, a fragrant variety grown from one of the Humboldt seeds, was probably interbred with the single D. coccinea. A new scented species would not be introduced until the next century when the D. coronata was brought from Mexico to Germany in 1907.
The exact date the dahlia was introduced in the United States is uncertain. One of the first Dahlias in the USA may be the D. coccinea speciosissima grown by Mr William Leathe, of Cambridgeport, near Boston, around 1929. According to Edward Sayers "it attracted much admiration, and at that time was considered a very elegant flower, it was however soon eclipsed by that splendid scarlet, the Countess of Liverpool". However 9 cultivars were already listed in the catalog from Thornburn, 1825. And even earlier reference can be found in a catalogue from the Linnaean Botanical Garden, New York, 1820, that includes one scarlet, one purple, and two double orange Dahlias for sale.
Sayers stated that "No person has done more for the introduction and advancement of the culture of the Dahlia than George C. Thorburn, of New York, who yearly flowers many thousand plants at his place at Hallet's Cove, near Harlaem. The show there in the flowering season is a rich treat for the lovers of floriculture : for almost every variety can be seen growing in two large blocks or masses which lead from the road to the dwelling-house, and form a complete field of the Dahlia as a foreground to the house. Mr T. Hogg, Mr William Read, and many other well known florists, have also contributed much in the vicinity of New York, to the introduction of the Dahlia. Indeed so general has become the taste that almost every garden has its show of the Dahlia in the season." In Boston too there were many collections, a collection from the Messrs Hovey of Cambridgeport was also mentioned.
In 1835 Thomas Bridgeman, published a list of 160 double dahlias in his Florist's Guide. 60 of the choicest were supplied by Mr. G. C. Thornburn of Astoria, N.Y. who got most of them from contacts in the UK. Not a few of them had taken prices "at the English and American exhibitions".
"STARS OF DEVIL"
In 1872 J.T. van der Berg of Utrecht in the Netherlands, received a shipment of seeds and plants from a friend in Mexico. The entire shipment was badly rotted and appeared to be ruined, but van der Berg examined it carefully and found a small piece of root that seemed alive. He planted and carefully tended it; it grew into a plant that he identified as a dahlia. He made cuttings from the plant during the winter of 1872-1873. This was an entirely different type of flower, with a rich, red color and a high degree of doubling. In 1874 van der Berg catalogued it for sale, calling it Dahlia juarezii to honor Mexican President Benito Pablo Juarez, who had died the year before, and described it as "...equal to the beautiful color of the red poppy. Its form is very outstanding and different in every respect of all known dahlia flowers.".
This plant has perhaps had a greater influence on the popularity of the modern dahlia than any other. Called "Les Etoiles de Diable" (Stars of the Devil) in France and "Cactus dahlia" elsewhere, the edges of its petals rolled backwards, rather than forward, and this new form revolutionized the dahlia world. It was thought to be a distinct mutation since no other plant that resembled it could be found in the wild. Today it is assumed that D. juarezii had, at one time, existed in Mexico and subsequently disappeared. Nurserymen in Europe crossbred this plant with dahlias discovered earlier; the results became the progenitors of all modern dahlia hybrids today.
AWARD OF GARDEN MERIT (RHS)
As of 2015, 124 dahlia cultivars have gained the Royal Horticultural Society's Award of Garden Merit:
"Bednall beauty"
"Bishop of Llandaff"
"Clair de lune"
"David Howard"
"Ellen Huston"
"Fascination"
"Gallery art deco"
"Gallery Art Nouveau"
"Glorie van Heemstede"
"Honka"
"Moonfire"
"Twyning's After Eight"
USES
FLORICULTURE
The asterid eudicots contain two economically important geophyte genera, Dahlia and Liatris. Horticulturally the garden dahlia is usually treated as the cultigen D. variabilis Hort., which while being responsible for thousands of cultivars has an obscure taxonomic status.
OTHER
Today the dahlia is still considered one of the native ingredients in Oaxacan cuisine; several cultivars are still grown especially for their large, sweet potato-like tubers. Dacopa, an intense mocha-tasting extract from the roasted tubers, is used to flavor beverages throughout Central America.
In Europe and America, prior to the discovery of insulin in 1923, diabetics - as well as consumptives - were often given a substance called Atlantic starch or diabetic sugar, derived from inulin, a naturally occurring form of fruit sugar, extracted from dahlia tubers. Inulin is still used in clinical tests for kidney functionality.
WIKIPEDIA
Dahlia (UK /deɪliə/ or US /dɑːliə/) is a genus of bushy, tuberous, herbaceous perennial plants native to Mexico. A member of the Asteraceae (or Compositae), dicotyledonous plants, related species include the sunflower, daisy, chrysanthemum, and zinnia. There are 42 species of dahlia, with hybrids commonly grown as garden plants. Flower forms are variable, with one head per stem; these can be as small as 5.1 cm diameter or up to 30 cm ("dinner plate"). This great variety results from dahlias being octoploids—that is, they have eight sets of homologous chromosomes, whereas most plants have only two. In addition, dahlias also contain many transposons - genetic pieces that move from place to place upon an allele - which contributes to their manifesting such great diversity.
The stems are leafy, ranging in height from as low as 30 cm to more than 1.8–2.4 m. The majority of species do not produce scented flowers or cultivars. Like most plants that do not attract pollinating insects through scent, they are brightly colored, displaying most hues, with the exception of blue.
The dahlia was declared the national flower of Mexico in 1963. The tubers were grown as a food crop by the Aztecs, but this use largely died out after the Spanish Conquest. Attempts to introduce the tubers as a food crop in Europe were unsuccessful.
DESCRIPTION
Perennial plants, with mostly tuberous roots. While some have herbaceous stems, others have stems which lignify in the absence of secondary tissue and resprout following winter dormancy, allowing further seasons of growth. as a member of the Asteraceae the flower head is actually a composite (hence the older name Compositae) with both central disc florets and surrounding ray florets. Each floret is a flower in its own right, but is often incorrectly described as a petal, particularly by horticulturalists. The modern mame Asteraceae refers to the appearance of a star with surrounding rays.
TAXONOMY
HISTORY
EARLY HISTORY
Spaniards reported finding the plants growing in Mexico in 1525, but the earliest known description is by Francisco Hernández, physician to Philip II, who was ordered to visit Mexico in 1570 to study the "natural products of that country". They were used as a source of food by the indigenous peoples, and were both gathered in the wild and cultivated. The Aztecs used them to treat epilepsy, and employed the long hollow stem of the (Dahlia imperalis) for water pipes. The indigenous peoples variously identified the plants as "Chichipatl" (Toltecs) and "Acocotle" or "Cocoxochitl" (Aztecs). From Hernandez' perception of Aztec, to Spanish, through various other translations, the word is "water cane", "water pipe", "water pipe flower", "hollow stem flower" and "cane flower". All these refer to the hollowness of the plants' stem.Hernandez described two varieties of dahlias (the pinwheel-like Dahlia pinnata and the huge Dahlia imperialis) as well as other medicinal plants of New Spain. Francisco Dominguez, a Hidalgo gentleman who accompanied Hernandez on part of his seven-year study, made a series of drawings to supplement the four volume report. Three of his drawings showed plants with flowers: two resembled the modern bedding dahlia, and one resembled the species Dahlia merki; all displayed a high degree of doubleness. In 1578 the manuscript, entitled Nova Plantarum, Animalium et Mineralium Mexicanorum Historia, was sent back to the Escorial in Madrid; they were not translated into Latin by Francisco Ximenes until 1615. In 1640, Francisco Cesi, President of the Academia Linei of Rome, bought the Ximenes translation, and after annotating it, published it in 1649-1651 in two volumes as Rerum Medicarum Novae Hispaniae Thesaurus Seu Nova Plantarium, Animalium et Mineraliuím Mexicanorum Historia. The original manuscripts were destroyed in a fire in the mid-1600s.
EUROPEAN INTRODUCTION
In 1787, the French botanist Nicolas-Joseph Thiéry de Menonville, sent to Mexico to steal the cochineal insect valued for its scarlet dye, reported the strangely beautiful flowers he had seen growing in a garden in Oaxaca. In 1789, Vicente Cervantes, Director of the Botanical Garden at Mexico City, sent "plant parts" to Abbe Antonio José Cavanilles, Director of the Royal Gardens of Madrid. Cavanilles flowered one plant that same year, then the second one a year later. In 1791 he called the new growths "Dahlia" for Anders Dahl. The first plant was called Dahlia pinnata after its pinnate foliage; the second, Dahlia rosea for its rose-purple color. In 1796 Cavanilles flowered a third plant from the parts sent by Cervantes, which he named Dahlia coccinea for its scarlet color.In 1798, Cavanilles sent D. Pinnata seeds to Parma, Italy. That year, the Marchioness of Bute, wife of The Earl of Bute, the English Ambassador to Spain, obtained a few seeds from Cavanilles and sent them to Kew Gardens, where they flowered but were lost after two to three years. In the following years Madrid sent seeds to Berlin and Dresden in Germany, and to Turin and Thiene in Italy. In 1802, Cavanilles sent tubers of "these three" (D. pinnata, D. rosea, D. coccinea) to Swiss botanist Augustin Pyramus de Candolle at University of Montpelier in France, Andre Thouin at the Jardin des Plantes in Paris and Scottish botanist William Aiton at Kew Gardens. That same year, John Fraser, English nurseryman and later botanical collector to the Czar of Russia, brought D. coccinea seeds from Paris to the Apothecaries Gardens in England, where they flowered in his greenhouse a year later, providing Botanical Magazine with an illustration.In 1804, a new species, Dahlia sambucifolia, was successfully grown at Holland House, Kensington. Whilst in Madrid in 1804, Lady Holland was given either dahlia seeds or tubers by Cavanilles. She sent them back to England, to Lord Holland's librarian Mr Buonaiuti at Holland House, who successfully raised the plants. A year later, Buonaiuti produced two double flowers. The plants raised in 1804 did not survive; new stock was brought from France in 1815. In 1824, Lord Holland sent his wife a note containing the following verse:
"The dahlia you brought to our isle
Your praises for ever shall speak;
Mid gardens as sweet as your smile,
And in colour as bright as your cheek."
In 1805, German naturalist Alexander von Humboldt sent more seeds from Mexico to Aiton in England, Thouin in Paris, and Christoph Friedrich Otto, director of the Berlin Botanical Garden. More significantly, he sent seeds to botanist Carl Ludwig Willdenow in Germany. Willdenow now reclassified the rapidly growing number of species, changing the genus from Dahlia to Georgina; after naturalist Johann Gottlieb Georgi. He combined the Cavanilles species D. pinnata and D. rosea under the name of Georgina variabilis; D. coccinea was still held to be a separate species, which he renamed Georgina coccinea.
CLASSIFICATION
Since 1789 when Cavanilles first flowered the dahlia in Europe, there has been an ongoing effort by many growers, botanists and taxonomists, to determine the development of the dahlia to modern times. At least 85 species have been reported: approximately 25 of these were first reported from the wild, the remainder appeared in gardens in Europe. They were considered hybrids, the results of crossing between previously reported species, or developed from the seeds sent by Humboldt from Mexico in 1805, or perhaps from some other undocumented seeds that had found their way to Europe. Several of these were soon discovered to be identical with earlier reported species, but the greatest number are new varieties. Morphological variation is highly pronounced in the dahlia. William John Cooper Lawrence, who hybridized hundreds of families of dahlias in the 1920s, stated: "I have not yet seen any two plants in the families I have raised which were not to be distinguished one from the other. Constant reclassification of the 85 reported species has resulted in a considerably smaller number of distinct species, as there is a great deal of disagreement today between systematists over classification.
In 1829, all species growing in Europe were reclassified under an all-encompassing name of D. variabilis, Desf., though this is not an accepted name. Through the interspecies cross of the Humboldt seeds and the Cavanilles species, 22 new species were reported by that year, all of which had been classified in different ways by several different taxonomists, creating considerable confusion as to which species was which.
In 1830 William Smith suggested that all dahlia species could be divided into two groups for color, red-tinged and purple-tinged. In investigating this idea Lawrence determined that with the exception of D. variabilis, all dahlia species may be assigned to one of two groups for flower-colour: Group I (ivory-magenta) or Group II (yellow-orange-scarlet).
CIRCUMSCRIPTION
The genus Dahlia is situated in the Asteroideae subfamily of the Asteraceae, in the Coreopsideae tribe. Within that tribe it is the second largest genus, after Coreopsis, and appears as a well defined clade within the Coreopsideae.
SUBDIVISION
INFRAGENERIC SUBDIVISION
Sherff (1955), in the first modern taxonomy described three sections for the 18 species he recognised, Pseudodendron, Epiphytum and Dahlia. By 1969 Sørensen recognised 29 species and four sections by splitting off Entemophyllon from section Dahlia. By contrast Giannasi (1975) using a phytochemical analysis based on flavonoids, reduced the genus to just two sections, Entemophyllon and Dahlia, the latter having three subsections, Pseudodendron, Dahlia, and Merckii. Sørensen then issued a further revision in 1980, incorporating subsection Merckii in his original section Dahlia. When he described two new species in the 1980s (Dahlia tubulata and D. congestifolia), he placed them within his existing sections. A further species, Dahlia sorensenii was added by Hansen and Hjerting in (1996). At the same time they demonstrated that Dahlia pinnata should more properly be designated D. x pinnata. D. x pinnata was shown to actually be a variant of D. sorensenii that had acquired hybrid qualities before it was introduced to Europe in the sixteenth century and formally named by Cavanilles. The original wild D. pinnata is presumed extinct. Further species continue to be described, Saar (2003) describing 35 species. However separation of the sections on morphological, cytologal and biocemical criteria has not been entirely satisfactory.
To date these sectional divisions have not been fully supported phylogenetically, which demonstrate only section Entemophyllon as a distinct sectional clade. The other major grouping is the Core Dahlia Clade (CDC), which includes most of section Dahlia. The remainder of the species occupy what has been described as the Variable Root Clade (VRC) which includes the small section Pseudodendron but also the monotypic section Epiphytum and a number of species from within section Dahlia. Outside of these three clades lie D. tubulata and D. merckii as a polytomy.
Horticulturally the sections retain some usage, section Pseudodendron being referred to as 'Tree Dahlias', Epiphytum as the 'Vine Dahlia'. The remaining two herbaceous sections being distinguished by their pinnules, opposing (Dahlia) or alternating (Entemophyllon).
SECTIONS
Sections (including chromosome numbers), with geographical distribution;
- Epiphytum Sherff (2n = 32)
10 m tall climber with aerial roots 5 cm thick and up to more than 20 m long; pinnules opposite
1 species, D. macdougallii Sherff
Mexico: Oaxaca
- Entemophyllon P. D. Sorensen (2n = 34)
6 species
Mexico: Hidalgo, Nuevo León, Tamaulipas, Querétaro, Durango, San Luis Potosí
- Pseudodendron P. D. Sorensen (2n = 32)
3 species + D. excelsa of uncertain identity
Mexico: Chiapas, Guerrero, Jalisco, Michoacan, Oaxaca, and
Costa Rica, El Salvador, Guatemala & Colombia
- Dahlia (2n = 32, 36 or 64)
24 species
Mexico: Distrito Federal, Guerrero, Hidalgo, Morelos, Nuevo León, Puebla, San Luis Potosí, Tamaulipas, Veracruz, Oaxaca, Puebla, Chiapas, México, Huehuetenango, Chihuahua, Durango, Michoacan & Guatemala
Only Pseudodendron (D. imperialis) and Dahlia (D. australis, D. coccinea) occur outside Mexico.
SPECIES
There are currently 42 accepted species in the Dahlia genus, but new species continue to be described.
ETYMOLOGY
The naming of the plant itself has long been a subject of some confusion. Many sources state that the name "Dahlia" was bestowed by the pioneering Swedish botanist and taxonomist Carl Linnaeus to honor his late student, Anders Dahl, author of Observationes Botanicae. However, Linnaeus died in 1778, more than eleven years before the plant was introduced into Europe in 1789, so while it is generally agreed that the plant was named in 1791 in honor of Dahl, who had died two years before, Linnaeus could not have been the one who did so. It was probably Abbe Antonio Jose Cavanilles, Director of the Royal Gardens of Madrid, who should be credited with the attempt to scientifically define the genus, since he not only received the first specimens from Mexico in 1789, but named the first three species that flowered from the cuttings.
Regardless of who bestowed it, the name was not so easily established. In 1805, German botanist Carl Ludwig Willdenow, asserting that the genus Dahlia Thunb. (published a year after Cavanilles's genus and now considered a synonym of Trichocladus) was more widely accepted, changed the plants' genus from Dahlia to Georgina; after the German-born naturalist Johann Gottlieb Georgi, a professor at the Imperial Academy of Sciences of St. Petersburg, Russia. He also reclassified and renamed the first three species grown, and identified, by Cavanilles. It was not until 1810, in a published article, that he officially adopted the Cavanilles' original designation of Dahlia. However, the name Georgina still persisted in Germany for the next few decades.
"Dahl" is a homophone of the Swedish word "dal", or "valley"; although it is not a true translation, the plant is sometimes referred to as the "valley flower".
DISTRIBUTION AND HABITAT
Predominantly Mexico, but some species are found ranging as far south as northern South America. D. australis occurs at least as far south as southwestern Guatemala, while D. coccinea and D. imperialis also occur in parts of Central America and northern South America. Dahlia is a genus of the uplands and mountains, being found at elevations between 1,500 and 3,700 meters, in what has been described as a "pine-oak woodland" vegetative zone. Most species have limited ranges scattered throughout many mountain ranges in Mexico.
ECOLOGY
The commonest pollinators are bees and small beetles.
PESTS AND DISEASES
Slugs and snails are serious pests in some parts of the world, particularly in spring when new growth is emerging through the soil. Earwigs can also disfigure the blooms. The other main pests likely to be encountered are aphids (usually on young stems and immature flower buds), red spider mite (causing foliage mottling and discolouration, worse in hot and dry conditions) and capsid bugs (resulting in contortion and holes at growing tips). Diseases affecting dahlias include powdery mildew, grey mould (Botrytis cinerea), verticillium wilt, dahlia smut (Entyloma calendulae f. dahliae), phytophthora and some plant viruses. Dahlias are a source of food for the larvae of some Lepidoptera species including Angle Shades, Common Swift, Ghost Moth and Large Yellow Underwing.
CULTIVATION
Dahlias grow naturally in climates which do not experience frost (the tubers are hardy to USDA Zone 8), consequently they are not adapted to withstand sub-zero temperatures. However, their tuberous nature enables them to survive periods of dormancy, and this characteristic means that gardeners in temperate climates with frosts can grow dahlias successfully, provided the tubers are lifted from the ground and stored in cool yet frost-free conditions during the winter. Planting the tubers quite deep (10 – 15 cm) also provides some protection. When in active growth, modern dahlia hybrids perform most successfully in well-watered yet free-draining soils, in situations receiving plenty of sunlight. Taller cultivars usually require some form of staking as they grow, and all garden dahlias need deadheading regularly, once flowering commences.
HORTICURAL CLASSIFICATION
HISTORY
The inappropriate term D. variabilis is often used to describe the cultivars of Dahlia since the correct parentage remains obscure, but probably involves Dahlia coccinea. In 1846 the Caledonia Horticultural Society of Edinburgh offered a prize of 2,000 pounds to the first person succeeding in producing a blue dahlia. This has to date not been accomplished. While dahlias produce anthocyanin, an element necessary for the production of the blue, to achieve a true blue color in a plant, the anthocyanin delphinidin needs six hydroxyl groups. To date dahlias have only developed five, so the closest that breeders have come to achieving a "blue" specimen are variations of mauve, purples and lilac hues.
By the beginning of the twentieth century a number of different types were recognised. These terms were based on shape or colour, and the National Dahlia Society included cactus, pompon, single, show and fancy in its 1904 guide. Many national societies developed their own classification systems until 1962 when the International Horticultural Congress agreed to develop an internationally recognised system at it Brussels meeting that year, and subsequently in Maryland in 1966. This culminated in the 1969 publication of The International Register of Dahlia Names by the Royal Horticultural Society which became the central registering authority.
This system depended primarily on the visibility of the central disc, whether it was open centred or whether only ray florets were apparent centrally (double bloom). The double bloom cultivars were then subdivided according to the way in which they were folded along their longitudinal axis, flat, involute (curled inwards) or revolute (curling backwards). If the end of the ray floret was split, they were considered fimbriated. Based on these characteristics, nine groups were defined plua a tenth miscellaneous group for any cultivars not fitting the above characteristics. Fimbriated dahlias were added in 2004, and two further groups (Single and Double orchid) in 2007. The last group to be added, Peony, first appeared in 2012.
In many cases the bloom diametre was then used to further label certain groups from miniature through to giant. This practice was abandoned in 2012.
MODERN SYSTEM (RHS)
There are now more than 57,000 registered cultivars, which are officially registered through the Royal Horticultural Society (RHS). The official register is The International Register of Dahlia Names 1969 (1995 reprint) which is updated by annual supplements. The original 1969 registry published about 14,000 cultivars adding a further 1700 by 1986 and in 2003 there were 18,000. Since then about a hundred new cultivars are added annually.
FLOWER TYPE
The official RHS classification lists fourteen groups, grouped by flower type, together with the abbreviations used by the RHS;
Group 1 – Single-flowered dahlias (Sin) — Flower has a central disc with a single outer ring of florets (which may overlap) encircling it, and which may be rounded or pointed.
Group 2 – Anemone-flowered dahlias (Anem) — The centre of the flower consists of dense elongated tubular florets, longer than the disc florets of Single dahlias, while the outer parts have one or more rings of flatter ray florets. Disc absent.
Group 3 – Collerette dahlias (Col) — Large flat florets forming a single outer ring around a central disc and which may overlap a smaller circle of florets closer to the centre, which have the appearance of a collar.
Group 4 – Waterlily dahlias (WL) — Double blooms, broad sparse curved, slightly curved or flat florets and very shallow in depth compared with other dahlias. Depth less than half the diameter of the bloom. Group 5 – Decorative dahlias (D) — Double blooms, ray florets broad, flat, involute no more than seventy five per cent of the longitudinal axis, slightly twisted and usually bluntly pointed. No visible central disc.
Group 6 – Ball dahlias (Ba)— Double blooms that are ball shaped or slightly flattened. Ray florets blunt or rounded at the tips, margins arranged spirally, involute for at least seventy five percent of the length of the florets. Larger than Pompons.
Group 7 – Pompon dahlias (Pom) — Double spherical miniature flowers made up entirely from florets that are curved inwards (involute) for their entire length (longitudinal axis), resembling a pompon.
Group 8 – Cactus dahlias (C) — Double blooms, ray florets pointed, with majority revolute (rolled) over more than fifty percent of their longitudinal axis, and straight or incurved. Narrower than Semi cactus.
Group 9 – Semi cactus dahlias (S–c)— Double blooms, very pointed ray florets, revolute for greater than twenty five percent and less than fifty percent of their longitudinal axis. Broad at the base and straight or incurved, almost spiky in appearance.
Group 10 – Miscellaneous dahlias (Misc) — not described in any other group.
Group 11 – Fimbriated dahlias (Fim) — ray florets evenly split or notched into two or more divisions, uniformly throughout the bloom, creating a fimbriated (fringed) effect. The petals may be flat, involute, revolute, straight, incurving or twisted.
Group 12 – Single Orchid (Star) dahlias (SinO) — single outer ring of florets surround a central disc. The ray florets are either involute or revolute.
Group 13 – Double Orchid dahlias (DblO) — Double blooms with triangular centres. The ray florets are narrowly lanceolate and are either involute or revolute. The central disc is absent.
Group 14 – Peony-flowered dahlias (P) — Large flowers with three or four rows of rays that are flattened and expanded and arranged irregularly. The rays surround a golden disc similar to that of Single dahlias.
FLOWER SIZE
Earlier versions of the registry subdivided some groups by flower size. Groups 4, 5, 8 and 9 were divided into five subgroups (A to E) from Giant to Miniature, and Group 6 into two subgroups, Small and Miniature. Dahlias were then described by Group and Subgroup, e.g. 5(d) ‘Ace Summer Sunset’. Some Dahlia Societies have continued this practice, but this is neither official nor standardised. As of 2013 The RHS uses two size descriptors
Dwarf Bedder (Dw.B.) — not usually exceeding 600 mm in height, e.g. 'Preston Park' (Sin/DwB)
Lilliput dahlias (Lil) — not usually exceeding 300 mm in height, with single, semi-double or double florets up to 26 mm in diameter. ("baby" or "top-mix" dahlias), e.g. 'Harvest Tiny Tot' (Misc/Lil)
Sizes can range from tiny micro dahlias with flowers less than 50mm to giants that are over 250mm in diameter. The groupings listed here are from the New Zealand Society.
Giant flowered cultivars have blooms with a diameter of over 250mm.
Large flowered cultivars have blooms with a diameter between 200mm-250mm.
Medium flowered cultivars have blooms with a diameter between 155mm-200mm.
Small flowered cultivars have blooms with a diameter between 115mm-155mm.
Miniature flowered cultivars have blooms with a diameter between 50mm-115mm.
Pompom flowered cultivars have blooms with a diameter less than 50mm.
In addition to the official classification and the terminology used by various dahlia societies, individual horticulturalists use a wide range of other descriptions, such as 'Incurved' and abbreviations in their catalogues, such as CO for Collarette.
BRANDING
Some plant growers include their brand name in the cultivar name. Thus Fides (part of the Dümmen Orange Group) in the Netherlands developed a series of cultivars which they named the Dahlinova Series, for example Dahlinova 'Carolina Burgundy'. These are Group 10 Miscellaneous in the RHS classification scheme.
DOUBLE DAHLIAS
In 1805, several new species were reported with red, purple, lilac, and pale yellow coloring, and the first true double flower was produced in Belgium. One of the more popular concepts of dahlia history, and the basis for many different interpretations and confusion, is that all the original discoveries were single flowered types, which, through hybridization and selective breeding, produced double forms. Many of the species of dahlias then, and now, have single flowered blooms. coccinea, the third dahlia to bloom in Europe, was a single. But two of the three drawings of dahlias by Dominguez, made in Mexico between 1570–77, showed definite characteristics of doubling. In the early days of the dahlia in Europe, the word "double" simply designated flowers with more than one row of petals. The greatest effort was now directed to developing improved types of double dahlias.
During the years 1805 to 1810 several people claimed to have produced a double dahlia. In 1805 Henry C. Andrews made a drawing of such a plant in the collection of Lady Holland, grown from seedlings sent that year from Madrid. Like other doubles of the time it did not resemble the doubles of today. The first modern double, or full double, appeared in Belgium; M. Donckelaar, Director of the Botanic Garden at Louvain, selected plants for that characteristic, and within a few years secured three fully double forms. By 1826 double varieties were being grown almost exclusively, and there was very little interest in the single forms. Up to this time all the so-called double dahlias had been purple, or tinged with purple, and it was doubted if a variety untinged with that color was obtainable.
In 1843, scented single forms of dahlias were first reported in Neu Verbass, Austria. D. crocea, a fragrant variety grown from one of the Humboldt seeds, was probably interbred with the single D. coccinea. A new scented species would not be introduced until the next century when the D. coronata was brought from Mexico to Germany in 1907.
The exact date the dahlia was introduced in the United States is uncertain. One of the first Dahlias in the USA may be the D. coccinea speciosissima grown by Mr William Leathe, of Cambridgeport, near Boston, around 1929. According to Edward Sayers "it attracted much admiration, and at that time was considered a very elegant flower, it was however soon eclipsed by that splendid scarlet, the Countess of Liverpool". However 9 cultivars were already listed in the catalog from Thornburn, 1825. And even earlier reference can be found in a catalogue from the Linnaean Botanical Garden, New York, 1820, that includes one scarlet, one purple, and two double orange Dahlias for sale.
Sayers stated that "No person has done more for the introduction and advancement of the culture of the Dahlia than George C. Thorburn, of New York, who yearly flowers many thousand plants at his place at Hallet's Cove, near Harlaem. The show there in the flowering season is a rich treat for the lovers of floriculture : for almost every variety can be seen growing in two large blocks or masses which lead from the road to the dwelling-house, and form a complete field of the Dahlia as a foreground to the house. Mr T. Hogg, Mr William Read, and many other well known florists, have also contributed much in the vicinity of New York, to the introduction of the Dahlia. Indeed so general has become the taste that almost every garden has its show of the Dahlia in the season." In Boston too there were many collections, a collection from the Messrs Hovey of Cambridgeport was also mentioned.
In 1835 Thomas Bridgeman, published a list of 160 double dahlias in his Florist's Guide. 60 of the choicest were supplied by Mr. G. C. Thornburn of Astoria, N.Y. who got most of them from contacts in the UK. Not a few of them had taken prices "at the English and American exhibitions".
"STARS OF DEVIL"
In 1872 J.T. van der Berg of Utrecht in the Netherlands, received a shipment of seeds and plants from a friend in Mexico. The entire shipment was badly rotted and appeared to be ruined, but van der Berg examined it carefully and found a small piece of root that seemed alive. He planted and carefully tended it; it grew into a plant that he identified as a dahlia. He made cuttings from the plant during the winter of 1872-1873. This was an entirely different type of flower, with a rich, red color and a high degree of doubling. In 1874 van der Berg catalogued it for sale, calling it Dahlia juarezii to honor Mexican President Benito Pablo Juarez, who had died the year before, and described it as "...equal to the beautiful color of the red poppy. Its form is very outstanding and different in every respect of all known dahlia flowers.".
This plant has perhaps had a greater influence on the popularity of the modern dahlia than any other. Called "Les Etoiles de Diable" (Stars of the Devil) in France and "Cactus dahlia" elsewhere, the edges of its petals rolled backwards, rather than forward, and this new form revolutionized the dahlia world. It was thought to be a distinct mutation since no other plant that resembled it could be found in the wild. Today it is assumed that D. juarezii had, at one time, existed in Mexico and subsequently disappeared. Nurserymen in Europe crossbred this plant with dahlias discovered earlier; the results became the progenitors of all modern dahlia hybrids today.
AWARD OF GARDEN MERIT (RHS)
As of 2015, 124 dahlia cultivars have gained the Royal Horticultural Society's Award of Garden Merit:
"Bednall beauty"
"Bishop of Llandaff"
"Clair de lune"
"David Howard"
"Ellen Huston"
"Fascination"
"Gallery art deco"
"Gallery Art Nouveau"
"Glorie van Heemstede"
"Honka"
"Moonfire"
"Twyning's After Eight"
USES
FLORICULTURE
The asterid eudicots contain two economically important geophyte genera, Dahlia and Liatris. Horticulturally the garden dahlia is usually treated as the cultigen D. variabilis Hort., which while being responsible for thousands of cultivars has an obscure taxonomic status.
OTHER
Today the dahlia is still considered one of the native ingredients in Oaxacan cuisine; several cultivars are still grown especially for their large, sweet potato-like tubers. Dacopa, an intense mocha-tasting extract from the roasted tubers, is used to flavor beverages throughout Central America.
In Europe and America, prior to the discovery of insulin in 1923, diabetics - as well as consumptives - were often given a substance called Atlantic starch or diabetic sugar, derived from inulin, a naturally occurring form of fruit sugar, extracted from dahlia tubers. Inulin is still used in clinical tests for kidney functionality.
WIKIPEDIA