Euphorbia is a very large and diverse genus of flowering plants, commonly called spurge, in the family Euphorbiaceae. "Euphorbia" is sometimes used in ordinary English to collectively refer to all members of Euphorbiaceae (in deference to the type genus), not just to members of the genus.

 

Euphorbias range from tiny annual plants to large and long-lived trees. with perhaps the tallest being Euphorbia ampliphylla at 30 m (98 ft) or more. The genus has roughly 2,000 members, making it one of the largest genera of flowering plants. It also has one of the largest ranges of chromosome counts, along with Rumex and Senecio. Euphorbia antiquorum is the type species for the genus Euphorbia. It was first described by Carl Linnaeus in 1753 in Species Plantarum.

 

Some euphorbias are widely available commercially, such as poinsettias at Christmas. Some are commonly cultivated as ornamentals, or collected and highly valued for the aesthetic appearance of their unique floral structures, such as the crown of thorns plant (Euphorbia milii). Succulent euphorbias from the deserts of Southern Africa and Madagascar have evolved physical characteristics and forms similar to cacti of North and South America, so they are often incorrectly referred to as cacti. Some are used as ornamentals in landscaping, because of beautiful or striking overall forms, and drought and heat tolerance.

 

Euphorbia all share the feature of having a poisonous, latex-like sap and unique floral structures When viewed as a whole, the head of flowers looks like a single flower (a pseudanthium). It has a unique kind of pseudanthium, called a cyathium, where each flower in the head is reduced to its barest essential part needed for sexual reproduction. The individual flowers are either male or female, with the male flowers reduced to only the stamen, and the females to the pistil. These flowers have no sepals, petals, or other parts that are typical of flowers in other kinds of plants. Structures supporting the flower head and other structures underneath have evolved to attract pollinators with nectar, and with shapes and colors that function in a way petals and other flower parts do in other flowers. It is the only genus of plants that has all three kinds of photosynthesis, CAM, C3 and C4.[7]

 

Etymology

The common name "spurge" derives from the Middle English/Old French espurge ("to purge"), due to the use of the plant's sap as a purgative. The botanical name Euphorbia derives from Euphorbos, the Greek physician of King Juba II of Numidia and Mauretania (52–50 BC – 23 AD), who married the daughter of Anthony and Cleopatra. Juba was a prolific writer on various subjects, including natural history. Euphorbos wrote that one of the cactus-like euphorbias (now called Euphorbia obtusifolia ssp. regis-jubae) was used as a powerful laxative. In 12 BC, Juba named this plant after his physician Euphorbos, as Augustus Caesar had dedicated a statue to the brother of Euphorbos, Antonius Musa, who was the personal physician of Augustus. In 1753, botanist and taxonomist Carl Linnaeus assigned the name Euphorbia to the entire genus in the physician's honor.

 

Description

The plants are annual, biennial or perennial herbs, woody shrubs, or trees with a caustic, poisonous milky latex. The roots are fine or thick and fleshy or tuberous. Many species are more or less succulent, thorny, or unarmed. The main stem and mostly also the side arms of the succulent species are thick and fleshy, and often winged, 15–91 cm (6–36 in) tall. The succulent trees and large shrubs are mostly confined to southern and eastern Africa, but Euphorbia neutra is native to the Caatinga of Brazil and Euphorbia royleana is found in the Himalayan foothills.[14] The deciduous[citation needed] leaves may be opposite, alternate, or in whorls. In succulent species, the leaves are mostly small and short-lived. The stipules are mostly small, partly transformed into spines or glands, or missing.

 

Inflorescence and fruit

Like all members of the family Euphorbiaceae, spurges have unisexual flowers.

 

In Euphorbia, flowers occur in a head, called the cyathium (plural cyathia). Each male or female flower in the cyathium head has only its essential sexual part, in males the stamen, and in females the pistil. The flowers do not have sepals, petals, or nectar to attract pollinators, although other nonflower parts of the plant have an appearance and nectar glands with similar roles. Euphorbias are the only plants known to have this kind of flower head.

 

Nectar glands and nectar that attract pollinators are held in the involucre, a cup-like part below and supporting the cyathium head. The "involucre" in the genus Euphorbia is not to be confused with the "involucre" in family Asteraceae members, which is a collection of bracts called phyllaries, which surround and encase the unopened flower head, then support the receptacle under it after the flower head opens.

 

The involucre is above and supported by bract-like modified leaf structures (usually in pairs)[citation needed] called cyathophylls', or cyathial leaves. The cyathophyll often has a superficial appearance of being petals of a flower.

 

Euphorbia flowers are tiny, and the variation attracting different pollinators, with different forms and colors occurs, in the cyathium, involucre, cyathophyll, or additional parts such as glands that attached to these.

 

The collection of many flowers may be shaped and arranged to appear collectively as a single individual flower, sometimes called a pseudanthium in the Asteraceae, and also in Euphorbia.

 

The majority of species are monoecious (bearing male and female flowers on the same plant), although some are dioecious with male and female flowers occurring on different plants. It is not unusual for the central cyathia of a cyme to be purely male, and for lateral cyathia to carry both sexes. Sometimes, young plants or those growing under unfavorable conditions are male only, and only produce female flowers in the cyathia with maturity or as growing conditions improve.

 

The female flowers reduced to a single pistil usually split into three parts, often with two stigmas at each tip.[citation needed] Male flowers often have anthers in twos.[citation needed] Nectar glands usually occur in fives, may be as few as one,[16] and may be fused into a "U" shape. The cyathophylls often occur in twos, are leaf-like, and may be showy and brightly coloured and attractive to pollinators, or be reduced to barely visible tiny scales.

 

The fruits are three- or rarely two-compartment capsules, sometimes fleshy, but almost always ripening to a woody container that then splits open, sometimes explosively. The seeds are four-angled, oval, or spherical, and some species have a caruncle.

 

Xerophytes and succulents

In the genus Euphorbia, succulence in the species has often evolved divergently and to differing degrees. Sometimes, it is difficult to decide, and is a question of interpretation, whether or not a species is really succulent or "only" xerophytic. In some cases, especially with geophytes, plants closely related to the succulents are normal herbs. About 850 species are succulent in the strictest sense. If one includes slightly succulent and xerophytic species, this figure rises to about 1000, representing about 45% of all Euphorbia species.

 

Irritants

The milky sap of spurges (called "latex") evolved as a deterrent to herbivores. It is white, and transparent when dry, except in E. abdelkuri, where it is yellow. The pressurized sap seeps from the slightest wound and congeals after a few minutes in air. The skin-irritating and caustic effects are largely caused by varying amounts of diterpenes. Triterpenes such as betulin and corresponding esters are other major components of the latex. In contact with mucous membranes (eyes, nose, mouth), the latex can produce extremely painful inflammation. The sap has also been known to cause mild to extreme Keratouveitis, which affects vision. Therefore, spurges should be handled with caution and kept away from children and pets. Wearing eye protection while working in close contact with Euphorbia is advised.[18] Latex on skin should be washed off immediately and thoroughly. Congealed latex is insoluble in water, but can be removed with an emulsifier such as milk or soap. A physician should be consulted if inflammation occurs, as severe eye damage including permanent blindness may result from exposure to the sap.

 

The poisonous qualities were well known: in the Ethiopian Kebra Nagast, the serpent king Arwe is killed with juice from the Euphorbia.

 

Uses

Several spurges are grown as garden plants, among them poinsettia (E. pulcherrima) and the succulent E. trigona. E. pekinensis (Chinese: 大戟; pinyin: dàjǐ) is used in traditional Chinese medicine, where it is regarded as one of the 50 fundamental herbs. Several Euphorbia species are used as food plants by the larvae of some Lepidoptera (butterflies and moths), like the spurge hawkmoths (Hyles euphorbiae and Hyles tithymali), as well as the giant leopard moth.

 

Ingenol mebutate, a drug used to treat actinic keratosis, is a diterpenoid found in Euphorbia peplus.

 

Euphorbias are often used as hedging plants in many parts of Africa.

Among laypeople, Euphorbia species are among the plant taxa most commonly confused with cacti, especially the stem succulents. Euphorbias secrete a sticky, milky-white fluid with latex, but cacti do not. Individual flowers of euphorbias are usually tiny and nondescript (although structures around the individual flowers may not be), without petals and sepals, unlike cacti, which often have fantastically showy flowers. Euphorbias from desert habitats with growth forms similar to cacti have thorns, which are different from the spines of cacti.

 

Systematics and taxonomy

The present taxon "Euphorbia" corresponds to its own former subtribe, the Euphorbiinae.[citation needed] It has over 2000 species. Morphological description using the presence of a cyathium (see section above) is consistent with nuclear and chloroplast DNA sequence data in testing of about 10% of its members. This testing supports inclusion of formerly other genera as being best placed in this single genus, including Chamaesyce, Monadenium, Pedilanthus, and poinsettia (E. pulcherrima).

 

Genetic tests have shown that similar flower head structures or forms within the genus, might not mean close ancestry within the genus. The genetic data show that within the genus, convergent evolution of inflorescence structures may be from ancestral subunits that are not related. So using morphology within the genus becomes problematic for further subgeneric grouping. As stated on the Euphorbia Planetary Biodiversity Inventory project webpage:

 

Previous morphologically based delimitations of subgenera or sections within the genus should not be taken at face value. The genus is in fact rife with striking examples of morphological convergence in cyathial and vegetative features, which justifies a global approach to studying the genus to obtain a proper phylogenetic understanding of the whole group.... The bottom line is that a number of clades have been placed inside or outside of Euphorbia at different times... few of the subgeneric circumscriptions hold up under DNA sequence analysis.

 

According to a 2002 publication on studies of DNA sequence data, most of the smaller "satellite genera" around the huge genus Euphorbia nest deep within the latter. Consequently, these taxa, namely the never generally accepted genus Chamaesyce, as well as the smaller genera Cubanthus, Elaeophorbia, Endadenium, Monadenium, Synadenium, and Pedilanthus were transferred to Euphorbia. The entire subtribe Euphorbiinae now consists solely of the genus Euphorbia.

 

Selected species

See List of Euphorbia species for complete list.

 

Euphorbia albomarginata – rattlesnake weed, white-margined sandmat

Euphorbia amygdaloides – wood spurge

Euphorbia antisyphilitica – candelilla

Euphorbia balsamifera – sweet tabaiba (Canary Islands)

Euphorbia bulbispina

Euphorbia caducifolia – leafless milk hedge

Euphorbia canariensis – Canary Island spurge, Hercules club (Canary Islands)

Euphorbia candelabrum – candelabra tree of East Africa

Euphorbia caput-medusae – Medusa's head (South Africa)

Euphorbia ceratocarpa – (Sicily and southern Italy)

Euphorbia characias – Mediterranean spurge

Euphorbia coerulescens - blue euphorbia

Euphorbia cotinifolia – copper tree

Euphorbia cyathophora – fire-on-the-mountain

Euphorbia cyparissias – Cypress spurge

Euphorbia decidua

Euphorbia dendroides – tree spurge

Euphorbia epithymoides – cushion spurge

Euphorbia esula – leafy spurge

Euphorbia franckiana

Euphorbia fulgens – scarlet plume

Euphorbia grantii – African milk bush

Euphorbia gregersenii – Gregersen's spurge

Euphorbia griffithii – Griffith's spurge

Euphorbia helioscopia – sun spurge

Euphorbia heterophylla – painted euphorbia, desert poinsettia, fireplant, paint leaf, kaliko

Euphorbia hirta – asthma-plant

Euphorbia hispida

Euphorbia horrida – African milk barrel

Euphorbia ingens – candelabra tree

Euphorbia labatii

Euphorbia lactea – mottled spurge, frilled fan, elkhorn

Euphorbia lathyris – caper spurge, paper spurge, gopher spurge, gopher plant, mole plant

Euphorbia leuconeura – Madagascar jewel

Euphorbia maculata – spotted spurge, prostrate spurge

Euphorbia marginata – snow on the mountain

Euphorbia mammillaris

Euphorbia maritae

Euphorbia milii – crown-of-thorns, Christ plant

Euphorbia misera – cliff spurge, Baja California, Southern California

Euphorbia myrsinites – myrtle spurge, creeping spurge, donkey tail

Euphorbia nivulia – leafy milk hedge

Euphorbia obesa

Euphorbia paralias – sea spurge

Euphorbia pekinensis – Peking spurge

Euphorbia peplis – purple spurge

Euphorbia peplus – petty spurge

Euphorbia polychroma – bonfire

Euphorbia psammogeton – sand spurge

Euphorbia pulcherrima – poinsettia, Mexican flame leaf, Christmas star, winter rose, noche buena, lalupatae, pascua, Atatürk çiçeği (Turkish)

Euphorbia purpurea – Darlington's glade spurge, glade spurge, or purple spurge

Euphorbia resinifera – resin spurge

Euphorbia rigida – gopher spurge, upright myrtle spurge

Euphorbia serrata – serrated spurge, sawtooth spurge

Euphorbia tirucalli – Indian tree spurge, milk bush, pencil tree, firestick

Euphorbia tithymaloides – devil's backbone, redbird cactus, cimora misha (Peru)

Euphorbia trigona – African milk tree, cathedral cactus, Abyssinian euphorbia

Euphorbia tuberosa

Euphorbia virosa – gifboom or poison tree

 

Hybrids

Euphorbia has been extensively hybridised for garden use, with many cultivars available commercially. Moreover, some hybrid plants have been found growing in the wild, for instance E. × martini Rouy, a cross of E. amygdaloides × E. characias subsp. characias, found in southern France.

 

Subgenera

The genus Euphorbia is one of the largest and most complex genera of flowering plants, and several botanists have made unsuccessful attempts to subdivide the genus into numerous smaller genera. According to the recent phylogenetic studies, Euphorbia can be divided into four subgenera, each containing several sections and groups. Of these, subgenus Esula is the most basal. The subgenera Chamaesyce and Euphorbia are probably sister taxa, but very closely related to subgenus Rhizanthium. Extensive xeromorph adaptations in all probability evolved several times; it is not known if the common ancestor of the cactus-like Rhizanthium and Euphorbia lineages had been xeromorphic—in which case a more normal morphology would have re-evolved namely in Chamaesyce—or whether extensive xeromorphism is entirely polyphyletic even to the level of the subgenera.

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Asteraceae (Compositae)

 

Asteridae: Asterales. The Asteraceae are herbs, shrubs, or less commonly trees and are arguably the largest family of flowering plants, comprising about 1,100 genera and 20,000 species that are characterized by having the flowers reduced and organized into an involucrate pseudanthium in the form of a head or capitulum. The leaves are alternate, opposite, or less commonly whorled, and range from simple to pinnately or palmately compound; stipules are absent

Photographed in the Dolomite Alps, northern Italy. Leontopodium nivale ssp. alpinum.

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographs by Lauren Ruth

The common sunflower (Helianthus annuus) is a species of large annual forb of the genus Helianthus. It is commonly grown as a crop for its edible oily seeds. Apart from cooking oil production, it is also used as livestock forage (as a meal or a silage plant), as bird food, in some industrial applications, and as an ornamental in domestic gardens. Wild H. annuus is a widely branched annual plant with many flower heads. The domestic sunflower, however, often possesses only a single large inflorescence (flower head) atop an unbranched stem.

 

Helianthus annuus (common sunflower) belong to the dicotyledonous category, distinguishing them from monocots. As dicots, sunflowers possess embryos with two veins, known as cotyledons, a characteristic feature that sets them apart. The veins in their leaves exhibit a net-like pattern, in contrast to monocots, which typically display parallel leaf veins.

 

Etymology

In the binomial name Helianthus annuus the genus name is derived from the Greek ἥλιος : hḗlios 'sun' and ἄνθος : ánthos 'flower'. The species name annuus means 'annual' in Latin.

 

Domestication

The plant was first domesticated in the Americas. Sunflower seeds were brought to Europe from the Americas in the 16th century, where, along with sunflower oil, they became a widespread cooking ingredient. With time, the bulk of industrial-scale production has shifted to Eastern Europe, and (as of 2020) Russia and Ukraine together produce over half of worldwide seed production.

 

Description

The plant has an erect rough-hairy stem, reaching typical heights of 3 metres (10 feet). The tallest sunflower on record achieved 9.17 m (30 ft 1 in). Sunflower leaves are broad, coarsely toothed, rough and mostly alternate; those near the bottom are largest and commonly heart-shaped.

 

Flower

The plant flowers in summer. What is often called the "flower" of the sunflower is actually a "flower head" (pseudanthium), 7.5–12.5 centimetres (3–5 in) wide, of numerous small individual five-petaled flowers ("florets"). The outer flowers, which resemble petals, are called ray flowers. Each "petal" consists of a ligule composed of fused petals of an asymmetrical ray flower. They are sexually sterile and may be yellow, red, orange, or other colors. The spirally arranged flowers in the center of the head are called disk flowers. These mature into fruit (sunflower "seeds").

 

The prairie sunflower (H. petiolaris) is similar in appearance to the wild common sunflower; the scales in its central disk are tipped by white hairs.

 

Heliotropism

A common misconception is that flowering sunflower heads track the Sun across the sky. Although immature flower buds exhibit this behaviour, the mature flowering heads point in a fixed (and typically easterly) direction throughout the day. This old misconception was disputed in 1597 by the English botanist John Gerard, who grew sunflowers in his famous herbal garden: "[some] have reported it to turn with the Sun, the which I could never observe, although I have endeavored to find out the truth of it." The uniform alignment of sunflower heads in a field might give some people the false impression that the flowers are tracking the Sun.

 

This alignment results from heliotropism in an earlier development stage, the young flower stage, before full maturity of flower heads (anthesis). Young sunflowers orient themselves in the direction of the sun. At dawn the head of the flower faces east and moves west throughout the day. When sunflowers reach full maturity they no longer follow the sun, and continuously face east. Young flowers reorient overnight to face east in anticipation of the morning. Their heliotropic motion is a circadian rhythm, synchronized by the sun, which continues if the sun disappears on cloudy days or if plants are moved to constant light. They are able to regulate their circadian rhythm in response to the blue-light emitted by a light source. If a sunflower plant in the bud stage is rotated 180°, the bud will be turning away from the sun for a few days, as resynchronization with the sun takes time.

 

When growth of the flower stalk stops and the flower is mature, the heliotropism also stops and the flower faces east from that moment onward. This eastward orientation allows rapid warming in the morning and, as a result, an increase in pollinator visits. Sunflowers do not have a pulvinus below their inflorescence. A pulvinus is a flexible segment in the leaf stalks (petiole) of some plant species and functions as a 'joint'. It effectuates leaf motion due to reversible changes in turgor pressure, which occurs without growth. The sensitive plant's closing leaves are a good example of reversible leaf movement via pulvinuli.

 

Floret arrangement

Generally, each floret is oriented toward the next by approximately the golden angle, 137.5°, producing a pattern of interconnecting spirals, where the number of left spirals and the number of right spirals are successive Fibonacci numbers. Typically, there are 34 spirals in one direction and 55 in the other; however, in a very large sunflower head there could be 89 in one direction and 144 in the other. This pattern produces the most efficient packing of seeds mathematically possible within the flower head.

 

Genome

The sunflower genome is diploid with a base chromosome number of 17 and an estimated genome size of 2,871–3,189 million base pairs. Some sources claim its true size is around 3.5 billion base pairs (slightly larger than the human genome).

 

Distribution and habitat

The plant was first domesticated in the Americas. Sunflowers grow best in fertile, moist, well-drained soil with heavy mulch. They often appear on dry open areas and foothills. Outside of cultivation, the common sunflower is found on moist clay based soils in areas with climates similar to Texas. In contrast the related Helianthus debilis and Helianthus petiolaris are found on drier, sandier soils.

 

The precise native range is difficult to determine. According to Plants of the World Online (POWO) it is native to Arizona, California, and Nevada in the present day United States and to all parts of Mexico except the Gulf Coast and southeast. Though not giving as great of detail, the Missouri Botanical Garden Plant Finder also lists it as native to the Western United States and Canada. The information published by the Biota of North America Program (BONAP) largely agrees with this, showing the common sunflower as native to states west of the Mississippi, though also listed as a noxious weed in Iowa, Minnesota, and Texas. Regardless of its original range it can now be found in almost every part of the world that is not tropical, desert, or tundra.

 

Ecology

Threats and diseases

Main article: List of sunflower diseases

One of the major threats that sunflowers face today is Fusarium, a filamentous fungus that is found largely in soil and plants. It is a pathogen that over the years has caused an increasing amount of damage and loss of sunflower crops, some as extensive as 80% of damaged crops.

 

Downy mildew is another disease to which sunflowers are susceptible. Its susceptibility to downy mildew is particular high due to the sunflower's way of growth and development. Sunflower seeds are generally planted only an inch deep in the ground. When such shallow planting is done in moist and soaked earth or soil, it increases the chances of diseases such as downy mildew.

 

Another major threat to sunflower crops is broomrape, a parasite that attacks the root of the sunflower and causes extensive damage to sunflower crops, as high as 100%.

 

Cultivation

In commercial planting, seeds are planted 45 cm (1+1⁄2 ft) apart and 2.5 cm (1 in) deep.

 

History

Common sunflower was one of several plants cultivated by Native Americans in prehistoric North America as part of the Eastern Agricultural Complex. Although it was commonly accepted that the sunflower was first domesticated in what is now the southeastern US, roughly 5,000 years ago, there is evidence that it was first domesticated in Mexico around 2600 BCE. These crops were found in Tabasco, Mexico, at the San Andres dig site. The earliest known examples in the US of a fully domesticated sunflower have been found in Tennessee, and date to around 2300 BCE. Other very early examples come from rockshelter sites in Eastern Kentucky. Many indigenous American peoples used the sunflower as the symbol of their solar deity, including the Aztecs and the Otomi of Mexico and the Incas in South America. In 1510, early Spanish explorers encountered the sunflower in the Americas and carried its seeds back to Europe. Of the four plants known to have been domesticated in eastern North America and to have become important agricultural commodities, the sunflower is currently the most economically important.

 

Research of phylogeographic relations and population demographic patterns across sunflowers has demonstrated that earlier cultivated sunflowers form a clade from wild populations from the Great Plains, which indicates that there was a single domestication event in central North America. Following the cultivated sunflower's origin, it may have gone through significant bottlenecks dating back to ~5,000 years ago.

 

In the 16th century the first crop breeds were brought from America to Europe by explorers. Domestic sunflower seeds have been found in Mexico, dating to 2100 BCE. Native American people grew sunflowers as a crop from Mexico to Southern Canada. They then were introduced to the Russian Empire, where oilseed cultivators were located, and the flowers were developed and grown on an industrial scale. The Russian Empire reintroduced this oilseed cultivation process to North America in the mid-20th century; North America began their commercial era of sunflower production and breeding. New breeds of the Helianthus spp. began to become more prominent in new geographical areas. During the 18th century, the use of sunflower oil became very popular in Russia, particularly with members of the Russian Orthodox Church, because only plant-based fats were allowed during Lent, according to fasting traditions. In the early 19th century, it was first commercialized in the village of Alexeyevka in Voronezh Governorate by the merchant named Daniil Bokaryov, who developed a technology suitable for its large-scale extraction, and quickly spread around. The town's coat of arms has included an image of a sunflower ever since.

 

Production

Sunflower seed production – 2020

Country(Millions of tonnes)

Russia13.3

Ukraine13.1

Argentina3.2

China2.4

Romania2.2

Turkey2.1

United States1.4

World50.2

Source: FAOSTAT of the United Nations

In 2020, world production of sunflower seeds was 50 million tonnes, led by Russia and Ukraine with 53% combined of the total (table).

 

Fertilizer use

Researchers have analyzed the impact of various nitrogen-based fertilizers on the growth of sunflowers. Ammonium nitrate was found to produce better nitrogen absorption than urea, which performed better in low-temperature areas.

 

Crop rotation

Sunflower cultivation typically uses crop rotation, often with cereals, soybean, or rapeseed. This reduces idle periods and increases total sunflower production and profitability.

 

Hybrids and cultivars

In today's market, most of the sunflower seeds provided or grown by farmers are hybrids. Hybrids or hybridized sunflowers are produced by cross-breeding different types and species, for example cultivated sunflowers with wild species. By doing so, new genetic recombinations are obtained ultimately leading to the production of new hybrid species. These hybrid species generally have a higher fitness and carry properties or characteristics that farmers look for, such as resistance to pathogens.

 

Hybrid, Helianthus annuus dwarf2 does not contain the hormone gibberellin and does not display heliotropic behavior. Plants treated with an external application of the hormone display a temporary restoration of elongation growth patterns. This growth pattern diminished by 35% 7–14 days after final treatment.

 

Hybrid male sterile and male fertile flowers that display heterogeneity have a low crossover of honeybee visitation. Sensory cues such as pollen odor, diameter of seed head, and height may influence pollinator visitation of pollinators that display constancy behavior patterns.

 

Sunflowers are grown as ornamentals in a domestic setting. Being easy to grow and producing spectacular results in any good, moist soil in full sun, they are a favourite subject for children. A large number of cultivars, of varying size and color, are now available to grow from seed. The following are cultivars of sunflowers (those marked agm have gained the Royal Horticultural Society's Award of Garden Merit):-

 

American Giant

Arnika

Autumn Beauty

Aztec Sun

Black Oil

Chianti Hybrid

Claret agm

Dwarf Sunspot

Evening Sun

Florenza

Giant Primrose

Gullick's Variety agm

Incredible

Indian Blanket Hybrid

Irish Eyes

Italian White

Kong Hybrid

Large Grey Stripe

Lemon Queen agm

Loddon Gold agm

Miss Mellish agm

Monarch agm

Mongolian Giant

Moon-Walker

Munchkin

Orange Sun

Pastiche agm

Peach Passion

Peredovik

Prado Red

Red Sun

Ring of Fire

Rostov

Russian Giant

Skyscraper

Solar Eclipse

Soraya

Strawberry Blonde

Sunny Hybrid

Sunsation Yellow

Sunshine

Taiyo

Tarahumara

Teddy Bear agm

Thousand Suns

Titan

Valentine agm

Velvet Queen

Yellow Disk

 

Uses

Sunflower "whole seed" (fruit) are sold as a snack food, raw or after roasting in ovens, with or without salt and/or seasonings added. Sunflower seeds can be processed into a peanut butter alternative, sunflower butter. It is also sold as food for birds and can be used directly in cooking and salads. Native Americans had multiple uses for sunflowers in the past, such as in bread, medical ointments, dyes and body paints.

 

Sunflower oil, extracted from the seeds, is used for cooking, as a carrier oil and to produce margarine and biodiesel, as it is cheaper than olive oil. A range of sunflower varieties exist with differing fatty acid compositions; some "high-oleic" types contain a higher level of monounsaturated fats in their oil than even olive oil. The oil is also sometimes used in soap. After World War I, during the Russian Civil War, people in Ukraine used sunflower seed oil in lamps as a substitute for kerosene due to shortages. The light from such a lamp has been described as "miserable" and "smoky."

 

The cake remaining after the seeds have been processed for oil is used as a livestock feed. The hulls resulting from the dehulling of the seeds before oil extraction can also be fed to domestic animals. Some recently developed cultivars have drooping heads. These cultivars are less attractive to gardeners growing the flowers as ornamental plants, but appeal to farmers, because they reduce bird damage and losses from some plant diseases. Sunflowers also produce latex, and are the subject of experiments to improve their suitability as an alternative crop for producing hypoallergenic rubber.

 

Traditionally, several Native American groups planted sunflowers on the north edges of their gardens as a "fourth sister" to the better-known three sisters combination of corn, beans, and squash.[61] Annual species are often planted for their allelopathic properties. It was also used by Native Americans to dress hair. Among the Zuni people, the fresh or dried root is chewed by the medicine man before sucking venom from a snakebite and applying a poultice to the wound. This compound poultice of the root is applied with much ceremony to rattlesnake bites.

 

However, for commercial farmers growing other commodity crops, the wild sunflower is often considered a weed. Especially in the Midwestern US, wild (perennial) species are often found in corn and soybean fields and can decrease yields. The decrease in yield can be attributed to the production of phenolic compounds which are used to reduce competition for nutrients in nutrient-poor growing areas of the common sunflower.

 

Phytoremediation

Helianthus annuus can be used in phytoremediation to extract pollutants from soil such as lead and other heavy metals, such as cadmium, zinc, cesium, strontium, and uranium, and in rhizofiltration to neutralize radionuclides, such as caesium-137 and strontium-90 from a pond after the Chernobyl disaster. A similar campaign was mounted in response to the Fukushima Daiichi nuclear disaster.[

 

Culture

Vincent van Gogh – "Lausanne" Sunflowers (1888)

During the 19th century, it was believed that nearby plants of the species would protect a home from malaria.

 

The Zuni people use the blossoms ceremonially for anthropic worship. Sunflowers were also worshipped by the Incas because they viewed it as a symbol for the Sun.

 

The flowers are the subject of Vincent van Gogh's Sunflowers series of still-life paintings.

 

In July 2015, viable seeds were acquired from the field where Malaysia Airlines Flight 17 crashed on a year earlier and were grown in tribute to the 15 Dutch residents of Hilversum who were killed. Earlier that year, Fairfax chief correspondent Paul McGeough and photographer Kate Geraghty had collected 1.5 kg of sunflower seeds from the wreck site for family and friends of the 38 Australian victims, who aimed to give them a poignant symbol of hope.

 

On May 13, 2021, during the National Costume competition of the Miss Universe 2020 beauty pageant, Miss Dominican Republic Kimberly Jiménez wore a "Goddess of Sunflowers" costume covered in gold and yellow rhinestones that included several real sunflowers sewn onto the fabric.

 

Modern stories often claim that in Greek mythology, the nymph Clytie transformed into a sunflower when she pined after her former lover Helios, the god of the sun, who spurned her and left her for another. However, sunflowers are not native to Greece or Italy, but to North America. The original story is about another flower, the heliotropium.

 

National and state symbol

The sunflower is the national flower of Ukraine. Ukrainians used sunflower as a main source of cooking oil instead of butter or lard forbidden by the Orthodox Church when observing Lent. They were planted to clean nuclear waste in Chernobyl. In June 1996, United States, Russia and Ukraine officials planted sunflowers at the Pervomaysk missile base where Soviet nuclear weapons were formerly placed.[69] During the Russo-Ukrainian War, a video widely shared on social media showed a Ukrainian woman confronting a Russian soldier, telling the latter to "take these seeds and put them in your pockets so at least sunflowers will grow when you all lie down here". The sunflower has since become a global symbol of resistance, unity, and hope.

 

The sunflower is also the state flower of the US state of Kansas, and one of the city flowers of Kitakyūshū, Japan.

 

Movement symbol

During the late 19th century, the flower was used as the symbol of the Aesthetic Movement.

 

The sunflower was chosen as the symbol of the Spiritualist Church, for many reasons, but mostly because of the (false) belief that the flowers turn toward the sun as "Spiritualism turns toward the light of truth". Modern Spiritualists often have art or jewelry with sunflower designs.

 

The sunflower is often used as a symbol of green ideology. The flower is also the symbol of the Vegan Society.

 

The sunflower is the symbol behind the Sunflower Movement, a 2014 mass protest in Taiwan.

 

The Hidden Disabilities Sunflower was first used as a visible symbol (typically worn on a lanyard) May 2016 at London Gatwick Airport. It has since come into common usage throughout the UK, and in the Commonwealth more generally.

Centaurea is a genus of over 700 species of herbaceous thistle-like flowering plants in the family Asteraceae. Members of the genus are found only north of the equator, mostly in the Eastern Hemisphere; the Middle East and surrounding regions are particularly species-rich. In the western United States, yellow starthistles are an invasive species. Around the year 1850, seeds from the plant had arrived to the state of California. It is believed that those seeds came from South America.

 

Common names

Common names for this genus are centaury, centory, starthistles, knapweeds, centaureas and the more ambiguous "bluets"; a vernacular name used for these plants in parts of England is "loggerheads" (common knapweed). The Plectocephalus group – possibly a distinct genus – is known as basketflowers. "Cornflower" is used for a few species, but that term more often specifically means either C. cyanus (the annual cornflower) or Centaurea montana (the perennial cornflower). The common name "centaury" is sometimes used, although this also refers to the unrelated plant genus Centaurium.

 

The name is said to be in reference to Chiron, the centaur of Greek mythology who discovered medicinal uses of a plant eventually called "centaury".

 

Description

Knapweeds are robust weedy plants. Their leaves, spiny in some species, are usually deeply divided into elongated lobes at least in the plants' lower part, becoming entire towards the top. The "flowers" (actually pseudanthium inflorescences) are diverse in colour, ranging from intense blues, reds and yellows to any mixture of these and lighter shades towards white. Often, the disk flowers are much darker or lighter than the ray flowers, which also differ in morphology and are sterile. Each pseudanthium sits atop a cup- or basket-like cluster of scaly bracts, hence the name "basketflowers". Many species, in particular those inhabiting more arid regions, have a long and strong taproot.

 

Certain knapweeds have a tendency to dominate large stretches of landscape together with a few other plants, typically one or two grasses and as many other large herbaceous plants. The common knapweed (C. nigra) for example is plentiful in the mesotrophic grasslands of England and nearby regions. It is most prominently found in pastures or meadows dominated by cock's-foot (Dactylis glomerata) as well as either of crested dog's-tail (Cynosurus cristatus) and false oat-grass (Arrhenatherum elatius). It is also often found in mesotrophic grassland on rendzinas and similar calcareous soils in association with glaucous sedge (Carex flacca), sheep's fescue (Festuca ovina), and either tor-grass (Brachypodium pinnatum) and rough hawkbit (Leontodon hispidus), or upright brome (Bromus erectus). In these grasslands, greater knapweed (C. scabiosa) is found much more rarely by comparison, often in association with red fescue (Festuca rubra) in addition to cock's-foot and false oat-grass.

 

Due to their habit of dominating ecosystems under good conditions, many Centaurea species can become invasive weeds in regions where they are not native. In parts of North America, diffuse knapweed (C. diffusa), spotted knapweed (C. maculosa) and yellow starthistle (C. solstitialis) cause severe problems in agriculture due to their uncontrolled spread. The seeds are typically transported by human traffic, in particular the tires of all-terrain vehicles. The two knapweeds are harmful mainly because they are strongly allelopathic, producing powerful toxins in their roots that stunt the growth of plants around them not adapted to this. Yellow starthistle, meanwhile, is inedible to most livestock due to its spines and apparently outright poisonous to horses and other equines. However, efficient methods of biological control by insect pests of these weeds have been developed; the knapweeds can also exploited to their detriment by targeted grazing. Controlled burning may also be used, though the timing is important to avoid the plants having seeded already, and neither allowing sufficient time for them to regrow from the rootstock.

 

Yet other species of Centaurea – mostly ones that occur between Italy and the Caucasus – are endemics of a single island or valley, and some of these are endangered. The Akamas Centaurea (Centaurea akamantis) of Cyprus is almost extinct, while the western Caucasus endemics C. leptophylla and C. straminicephala are at least very rare and C. hedgei and C. pecho from the same region are certainly not abundant either. The last four species would be adversely affected by the proposed Yusufeli Dam, which might actually destroy enough habitat to push the two rarer ones over the brink of extinction.

 

Centaurea are copious nectar producers, especially on high-lime soils. The high nectar yield of the genus makes it very attractive to insects such as butterflies – including the endangered Karner blue (Plebejus melissa samuelis) which visits introduced spotted knapweed – and day-flying moths – typically Zygaenidae, such as Zygaena loti or the six-spot burnet (Z. filipendulae). The larvae of some other Lepidoptera species use Centaurea species as food plants; see List of Lepidoptera that feed on Centaurea. Several of these are used in biological control of invasive knapweeds and starthistles.

 

Larvae of several true weevils (Curculionidae) of the subfamily Lixinae also feed on Centaurea. Some genera – such as Larinus whose larval food is flowerheads – have many species especially adapted to particular knapweeds or starthistle and are used in biological control too. These include the yellow starthistle flower weevil (L. curtus) for yellow starthistle, lesser knapweed flower weevil (L. minutus) for diffuse knapweed and blunt knapweed flower weevil (L. obtusus) for spotted knapweed. Broad-nosed seedhead weevil (Bangasternus fausti) larvae eat diffuse, spotted and squarrose knapweed (C. virgata ssp. squarrosa), while those of the yellow starthistle bud weevil (B. orientalis) do not seem to live on anything other than yellow starthistle and occasionally purple starthistle (C. calcitrapa). But perhaps most efficient in destroying developing yellow starthistle seedheads is the larva of the yellow starthistle hairy weevil (Eustenopus villosus). Knapweed root weevil (Cyphocleonus achates) larvae bore into the roots of spotted and to a lesser extentely diffuse knapweed, sometimes killing off the entire plant.

 

Also used in biological control are Tephritidae (peacock flies) whose larvae feed on Centaurea. Knapweed peacock fly (Chaetorellia acrolophi) larvae eat spotted knapweed and some other species. The yellow starthistle peacock fly (C. australis) has an initial generation each year which often uses cornflower (C. cyanus) as larval food; later generations switch to yellow starthistle. The flies are generally considered less efficient in destroying the growing seedheads than the weevils, but may be superior under certain conditions; employing flies and weevils in combination is expensive and does not noticeably increase their effect.

 

Use by humans

Although the genus may be considered by a quite significant number of relatively informed individuals to have an overall negative impact on human interests, particularly agricultural interests, the situation is not straightforward enough to simply declare the genus, or, at least, its most aggressively-spreading species, altogether negative. For instance, due to their moderate to high nectar production, which can occur over a comparatively long duration, many species of Centaurea are popular food sources for insects that may otherwise attack certain crops.[citation needed] It may be advisable for some types of farms to allow certain species in this genus, such as cornflower (C. cyanus) in a European setting, to grow adjacent to fields. Although they support and attract many types of beneficial life (not just beetles), these areas are known as beetle banks. When they are present, some pests may be drawn away from crops to them and predatory insects and arachnids that feed upon pest insects will be better-supported by these more naturalized areas. They additionally have the beneficial aspect of supporting pollinators, unlike many field crops such as maize. Moreover, being untreated with pesticides and providing more diversity, plants growing in more wild areas adjacent to farms produce more insects that attract and support birds which can also feed on pests that would harm crops. Insect production is especially high for beetle banks that have enough plants that serve in the role of host plant for immature insects, rather than just in the roles of adult food and/or shelter provision.

 

Some plants which are considered invasive or problematic in certain areas can have beneficial qualities that outweigh their negative qualities from a human and/or human agricultural point of view, although this sometimes requires some human management – particularly if adequate biological control has not been established for the more aggressive species. An example is wild parsnip, Pastinaca sativa, which produces florets that feed predatory (and other beneficial) insects as well as large tubular stems that provide winter shelter for native bees, wasps, and other organisms that can be beneficial for agriculture. The plant is considered invasive in some areas of the United States and is also often considered undesirable due to its ability to cause contact skin irritation. However, it also serves as a host plant for the black swallowtail butterfly, helps to bring nutrients up from soils with its deep taproot, and possesses evergreen foliage even in climate zones such as US zone 6. This foliage increases soil warmth and moisture which can be beneficial for certain types of life. Perhaps the most dramatic example of a generally disliked plant's beneficial qualities being usually overlooked is the often-despised ragwort, Jacobaea vulgaris, which topped the list by a large amount for nectar production in a UK study, with a production per floral unit of (2921 ± 448μg). This very high nectar production, coupled with its early blooming period, makes the plant helpful for the establishment of bee colonies in spring — a period that is often not well-served by commercial flower meadow seed mixes. It also has the situationally-beneficial quality of being a spring ephemeral, as well as an annual that lacks difficult-to-combat roots. Plants that provide necessary structural supports for invertebrate and small vertebrate predators can help to keep overall pest populations low.

 

The abundant nectar produced by C. solstitialis flowers attracts many pollinators. This is another reason for the success of the (situationally) highly invasive species. Due to genetic differences related to evolutionary adaption, not all members of Centaurea produce the same amount of nectar. Growing conditions, such as climate and soil, can have a very strong impact, even if the plants grow and flower. For instance, cornflower plants, Centaurea cyanus, produced 33% less seasonal nectar than Centaurea nigra in a UK study. C. nigra also ranked higher than ragwort in another UK study, although ragwort was still in the top 10 for yearly nectar production. The strong nectar production of certain members of the genus can be exploited to the farmer's advantage, possibly in combination with biological control. In particular, the yellow starthistle (C. solstitialis) as well as spotted knapweed (C. maculosa) are major honey plants for beekeepers. Monofloral honey from these plants is light and slightly tangy, and one of the finest honeys produced in the United States – due to its better availability, it is even fraudulently relabeled and sold as the scarce and expensive sourwood honey of the Appalachian Mountains. Placing beehives near stands of Centaurea will cause increased pollination. As most seedheads fail however when biocontrol pests have established themselves, the plants will bloom ever more abundantly in an attempt to replace the destroyed seedheads, to the point where they exhaust their resources in providing food for the pests (seeds), bees (pollen) and humans (honey). Output of allelopathic compounds is also liable to be reduced under such conditions – the plant has to compromise between allocating energy to reproduction and defense. This renders the weeds more likely to be suppressed by native vegetation or crops in the following years, especially if properly timed controlled burning[5] and/or targeted grazing by suitable livestock are also employed. While yellow starthistle and perhaps other species are toxic to equines, some other livestock may eat the non-spiny knapweeds with relish. In Europe, common knapweed (C. nigra) and globe knapweed (C. macrocephala) are locally important pollen sources for honeybees in mid-late summer.

 

8-Hydroxyquinoline has been identified as a main allelopathic compound produced by diffuse knapweed (C. diffusa); native North American plants are typically sensitive to it, while those of Eastern Europe and Asia Minor usually have coevolved with the knapweed and are little harmed if at all, aided by native microorganisms that break down or even feed on the abundantly secreted compound. Thus, 8-hydroxyquinoline is potentially useful to control American plants that have become invasive weeds in the diffuse knapweed's native range.

 

Arctiin, found in C. imperialis, has shown anticancer activity in laboratory studies. The roots of the long-lost C. foliosa, an endemic of Hatay Province (Turkey), are used in folk medicine, and other species are presumably too. A South Italian variety[verification needed] of the purple starthistle (C. calcitrapa) is traditionally consumed by ethnic Albanians (Arbëreshë people) in the Vulture area (southern Italy); e.g. in the Arbëreshë communities in Lucania the young whorls of C. calcitrapa are boiled and fried in mixtures with other weedy non-cultivated greens. According to research by the Michael Heinrich group at the Centre for Pharmacognosy and Phytotherapy (School of Pharmacy, University of London) "the antioxidant activity [...] of the young whorls of Centaurea calcitrapa, both in the DPPH and in the lipid peroxidation inhibition assays, [is] very interesting and [the] species should be investigated phytochemically and biochemically focusing on these properties". Extracts from C. calcitrapa were furthermore found to have significant xanthine oxidase (XO)-inhibiting activity.

 

Spotted knapweed as well as other species are rich in cnicin, a bitter compound found mainly in the leaves and often used to flavor the digestif amaro. In western Crete, Greece a local variety[verification needed] of C. calcitrapa called gourounaki (γουρουνάκι "little pig") also has its leaves eaten boiled by the locals. In the same island an endemic local species, C. idaea called katsoula (κατσούλα), tsita (τσίτα) or aspragatha (ασπραγκάθα), has its leaves eaten boiled by the locals too.

 

Some species are cultivated as ornamental plants in gardens. As regards other aspects of popular culture, cornflower (C. cyanus) is the floral emblem of Östergötland province (Sweden) – where is it called blåklint, literally "blue mountain" – and of Päijänne Tavastia region in Finland, where it is known as ruiskaunokki ("rye-beaks") or ruiskukka ("rye-flower"). It is also the national flower of Estonia where its local name rukkilill means "rye-lily", Belarus where it is called vałoška (Belarusian: валошка), and one of those of Germany where it is called Kornblume ("cornflower"). The origin of the name "caltrop" for the ancient low-tech area denial weapon is probably in some way connected with C. calcitrapa and its spiny seeds. This plant is attested to by the colloquial name "caltrop" at a time when the weapons were still called by their Roman name tribulus. Lastly, the color cornflower blue is named after C. cyanus. Cornflower is also used as a cut flower.

 

As namesake member of the subtribe Centaureinae of tribe Cardueae, the knapweeds are probably most closely related to genera such as Carthamus (distaff thistles), Cnicus (blessed thistle), Crupina (crupinas) or Notobasis (Syrian thistle), and somewhat less closely to most other thistles. The monotypic Cnicus seems in fact to properly belong in Centaurea.

 

Research in the late 20th century shows that Centaurea as traditionally defined is polyphyletic. A number of 19th- and 20th-century efforts to reorganize the genus were not successful, and it is not yet clear what the consequences of the recent research will be for classification of this genus and other related genera. The type species C. centaurium stands somewhat apart from the main lineage of knapweeds and thus the taxonomic consequences of a rearrangement might be severe, with hundreds of species needing to be moved to new genera. It has thus been proposed to change the type species to one of the main lineages to avoid this problem. What seems certain however is that the basketflowers – presently treated as a section Plectocephalus – will be reinstated as a distinct genus in the near future. The rock-centauries (Cheirolophus), formerly usually included in Centaurea, are now already treated as separate genus.

 

Better-known Centaurea species include:

 

Centaurea acaulis

Centaurea adpressa

Centaurea aegyptiaca

Centaurea aeolica

Centaurea aggregata

Centaurea akamantis – Akamas centaurea

Centaurea alba

Centaurea albonitens Turrill

Centaurea alpestris

Centaurea alpina

Centaurea ambigua

Centaurea amblyolepis

Centaurea americana – American basketflower, American starthistle

Centaurea ammocyanus

Centaurea antennata Dufour

Centaurea antiochia Boiss.

Centaurea aplolepa

Centaurea aplolepa subsp. carueliana

Centaurea appendicigera C.Koch

Centaurea argentea

Centaurea ascalonica

Centaurea aspera L. – rough starthistle

Centaurea atacamensis (Reiche) I.M.Johnst.

Centaurea atropurpurea

Centaurea ×aurata

Centaurea babylonica L.

Centaurea balsamita

Centaurea behen L. – ak behmen (Turkish)

Centaurea bella

Centaurea benedicta – Cnicus

Centaurea bieberseinii

Centaurea borjae

Centaurea bovina

Centaurea bracteata

Centaurea brevifimbriata Hub.-Mor.

Centaurea bulbosa

Centaurea busambarensis Guss.

Centaurea cachinalensis

Centaurea calcitrapa – purple starthistle, red starthistle, "caltrop"

Centaurea calcitrapoides

Centaurea cariensis Boiss.

Centaurea cariensiformis Hub.-Mor.

Centaurea caroli-henrici Gabrieljan & Dittrich

Centaurea centaurium L.

Centaurea chilensis

Centaurea cineraria – velvet centaurea, dusty miller

Centaurea clementei

Centaurea collina L.

Centaurea corymbosa

Centaurea crithmifolia

Centaurea crocodylium

Centaurea cyanoides J.Berggr. & Wahlenb.

Centaurea cyanus – cornflower, bachelor's button, boutonniere flower, hurtsickle, bluebottle, basketflower

Centaurea damascena

Centaurea debeauxii Gren. & Godr.

Centaurea demirizii Wagenitz

Centaurea depressa – low cornflower

Centaurea deusta

Centaurea diffusa – diffuse knapweed, white knapweed, tumble knapweed

Centaurea diluta – North African knapweed

Centaurea drabifolia Sm.

Centaurea drabifolioides Hub.-Mor.

Centaurea dschungarica

Centaurea emilae Hüseynova et Qaraxani[13]

Centaurea eriophora

Centaurea eryngioides

Centaurea filiformis

Centaurea fischeri Willd.

Centaurea floccosa

Centaurea foliosa Boiss. & Kotschy

Centaurea forojuliensis

Centaurea friderici Vis. – palagruška zečina (Croatian)

Centaurea gayana

Centaurea glaberrima Tausch

Centaurea glastifolia

Centaurea grinensis

Centaurea gymnocarpa

Centaurea haradjianii Wagenitz

Centaurea hedgei

Centaurea helenioides Boiss.

Centaurea hermannii F.Hermann

Centaurea horrida Badarò – fiordaliso spinoso (Italian)

Centaurea hyalolepis

Centaurea hypoleuca

Centaurea iberica – Iberian starthistle, Iberian knapweed

Centaurea idaea – katsoula, tsita (Cretan Greek)

Centaurea imperialis Hausskn. ex Bornm.

Centaurea jabukensis

Centaurea jacea – brown knapweed, brownray knapweed

Centaurea kasakorum

Centaurea kopetaghensis

Centaurea kotschyana Heuff.

Centaurea lanulata

Centaurea leptophylla

Centaurea leucophylla

Centaurea limbata

Centaurea lydia Boiss.

Centaurea macrocephala Puschk. ex Willd. – globe knapweed, Armenian basketflower

Centaurea maculosa – spotted knapweed (might belong in C. stoebe subsp. micranthos)

Centaurea mannagettae

Centaurea margaritalba Klok.

Centaurea marschalliana

Centaurea melitensis – Maltese starthistle; tocalote, tocolote (California)

Centaurea minor

Centaurea moschata – sweet sultan

Centaurea ×moncktonii C.E.Britton – meadow knapweed, protean knapweed (= C. ×pratensis Thuill non Salisb.)

Centaurea monocephala

Centaurea montana – montane knapweed, perennial cornflower, mountain cornflower, mountain bluet

Centaurea napifolia L. – fiordaliso romano (Italian)

Centaurea nervosa Rchb. ex Steud.

Centaurea nigra – common knapweed, black knapweed, lesser knapweed, hardheads

Centaurea nigrescens – Tyrol knapweed, short-fringed knapweed, Tyrol thistle

Centaurea nigrifimbria (C.Koch) Sosn.

Centaurea nivea (Bornm.) Wagenitz

Centaurea onopordifolia

Centaurea orientalis L.

Centaurea ornata Willd.

Centaurea ovina

Centaurea pallescens Delile

Centaurea paniculata L.

Centaurea parlatoris

Centaurea pecho

Centaurea phrygia – wig knapweed

Centaurea pindicola

Centaurea polypodiifolia

Centaurea ×pratensis Salisb. (C. jacea × C. nigra) – meadow knapweed

Centaurea procurrens

Centaurea ×psammogena G.Gayer. (C. diffusa × C. stoebe subsp. micranthos)

Centaurea pseudocaerulescens

Centaurea pseudophrygia C.A.Mey.

Centaurea pulcherrima Willd.

Centaurea pullata L.

Centaurea pumilio

Centaurea ragusina L.

Centaurea rigida

Centaurea rothrockii Greenm. – Mexican basketflower, Rothrock's basketflower, Rothrock's knapweed

Centaurea ruthenica

Centaurea rutifolia Sm.

Centaurea sadleriana – Pannonian knapweed

Centaurea salicifolia Bieb. ex Willd.

Centaurea scabiosa – greater knapweed

Centaurea scannensis

Centaurea scoparia

Centaurea scopulorum Boiss. & Heldr.

Centaurea seguenzae

Centaurea seridis L.

Centaurea sibirica

Centaurea simplicicaulis

Centaurea sinaica

Centaurea solstitialis – yellow starthistle, golden starthistle, yellow cockspur, St. Barnaby's thistle, Barnaby thistle

Centaurea speciosa

Centaurea sphaerocephala L.

Centaurea stenolepis

Centaurea stoebe L.

Centaurea stoebe subsp. micranthos (Gugler) Hayek

Centaurea straminicephala

Centaurea sulphurea – Sicilian starthistle

Centaurea tauromenitana Guss.

Centaurea tenoreana

Centaurea tommasinii

Centaurea transalpina Schleich. ex DC.

Centaurea tchihatcheffii — yanardöner (Turkish)

Centaurea trichocephala Bieb. ex Willd. – featherhead knapweed

Centaurea triniifolia

Centaurea triumfettii All.

Centaurea ucriae Lacaita

Centaurea uniflora Turra

Centaurea verbascifolia Vahl

Centaurea verutum L.

Centaurea virgata

Centaurea virgata subsp. squarrosa – squarrose knapweed

Centaurea wiedemanniana Fisch. & Mey.

Centaurea yozgatensis Wagenitz

Formerly placed here

Plant species placed in Centaurea in former times include:

 

Acroptilon repens – Russian knapweed (as C. repens)

Cheirolophus crassifolius – Maltese rock-centaury (as C. crassifolia, C. spathulata)

Femeniasia balearica (as C. balearica)

Volutaria muricata (as C. muricata)

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographs by Lauren Ruth

Centaurea is a genus of over 700 species of herbaceous thistle-like flowering plants in the family Asteraceae. Members of the genus are found only north of the equator, mostly in the Eastern Hemisphere; the Middle East and surrounding regions are particularly species-rich. In the western United States, yellow starthistles are an invasive species. Around the year 1850, seeds from the plant had arrived to the state of California. It is believed that those seeds came from South America.

 

Common names

Common names for this genus are centaury, centory, starthistles, knapweeds, centaureas and the more ambiguous "bluets"; a vernacular name used for these plants in parts of England is "loggerheads" (common knapweed). The Plectocephalus group – possibly a distinct genus – is known as basketflowers. "Cornflower" is used for a few species, but that term more often specifically means either C. cyanus (the annual cornflower) or Centaurea montana (the perennial cornflower). The common name "centaury" is sometimes used, although this also refers to the unrelated plant genus Centaurium.

 

The name is said to be in reference to Chiron, the centaur of Greek mythology who discovered medicinal uses of a plant eventually called "centaury".

 

Description

Knapweeds are robust weedy plants. Their leaves, spiny in some species, are usually deeply divided into elongated lobes at least in the plants' lower part, becoming entire towards the top. The "flowers" (actually pseudanthium inflorescences) are diverse in colour, ranging from intense blues, reds and yellows to any mixture of these and lighter shades towards white. Often, the disk flowers are much darker or lighter than the ray flowers, which also differ in morphology and are sterile. Each pseudanthium sits atop a cup- or basket-like cluster of scaly bracts, hence the name "basketflowers". Many species, in particular those inhabiting more arid regions, have a long and strong taproot.

 

Certain knapweeds have a tendency to dominate large stretches of landscape together with a few other plants, typically one or two grasses and as many other large herbaceous plants. The common knapweed (C. nigra) for example is plentiful in the mesotrophic grasslands of England and nearby regions. It is most prominently found in pastures or meadows dominated by cock's-foot (Dactylis glomerata) as well as either of crested dog's-tail (Cynosurus cristatus) and false oat-grass (Arrhenatherum elatius). It is also often found in mesotrophic grassland on rendzinas and similar calcareous soils in association with glaucous sedge (Carex flacca), sheep's fescue (Festuca ovina), and either tor-grass (Brachypodium pinnatum) and rough hawkbit (Leontodon hispidus), or upright brome (Bromus erectus). In these grasslands, greater knapweed (C. scabiosa) is found much more rarely by comparison, often in association with red fescue (Festuca rubra) in addition to cock's-foot and false oat-grass.

 

Due to their habit of dominating ecosystems under good conditions, many Centaurea species can become invasive weeds in regions where they are not native. In parts of North America, diffuse knapweed (C. diffusa), spotted knapweed (C. maculosa) and yellow starthistle (C. solstitialis) cause severe problems in agriculture due to their uncontrolled spread. The seeds are typically transported by human traffic, in particular the tires of all-terrain vehicles. The two knapweeds are harmful mainly because they are strongly allelopathic, producing powerful toxins in their roots that stunt the growth of plants around them not adapted to this. Yellow starthistle, meanwhile, is inedible to most livestock due to its spines and apparently outright poisonous to horses and other equines. However, efficient methods of biological control by insect pests of these weeds have been developed; the knapweeds can also exploited to their detriment by targeted grazing. Controlled burning may also be used, though the timing is important to avoid the plants having seeded already, and neither allowing sufficient time for them to regrow from the rootstock.

 

Yet other species of Centaurea – mostly ones that occur between Italy and the Caucasus – are endemics of a single island or valley, and some of these are endangered. The Akamas Centaurea (Centaurea akamantis) of Cyprus is almost extinct, while the western Caucasus endemics C. leptophylla and C. straminicephala are at least very rare and C. hedgei and C. pecho from the same region are certainly not abundant either. The last four species would be adversely affected by the proposed Yusufeli Dam, which might actually destroy enough habitat to push the two rarer ones over the brink of extinction.

 

Centaurea are copious nectar producers, especially on high-lime soils. The high nectar yield of the genus makes it very attractive to insects such as butterflies – including the endangered Karner blue (Plebejus melissa samuelis) which visits introduced spotted knapweed – and day-flying moths – typically Zygaenidae, such as Zygaena loti or the six-spot burnet (Z. filipendulae). The larvae of some other Lepidoptera species use Centaurea species as food plants; see List of Lepidoptera that feed on Centaurea. Several of these are used in biological control of invasive knapweeds and starthistles.

 

Larvae of several true weevils (Curculionidae) of the subfamily Lixinae also feed on Centaurea. Some genera – such as Larinus whose larval food is flowerheads – have many species especially adapted to particular knapweeds or starthistle and are used in biological control too. These include the yellow starthistle flower weevil (L. curtus) for yellow starthistle, lesser knapweed flower weevil (L. minutus) for diffuse knapweed and blunt knapweed flower weevil (L. obtusus) for spotted knapweed. Broad-nosed seedhead weevil (Bangasternus fausti) larvae eat diffuse, spotted and squarrose knapweed (C. virgata ssp. squarrosa), while those of the yellow starthistle bud weevil (B. orientalis) do not seem to live on anything other than yellow starthistle and occasionally purple starthistle (C. calcitrapa). But perhaps most efficient in destroying developing yellow starthistle seedheads is the larva of the yellow starthistle hairy weevil (Eustenopus villosus). Knapweed root weevil (Cyphocleonus achates) larvae bore into the roots of spotted and to a lesser extentely diffuse knapweed, sometimes killing off the entire plant.

 

Also used in biological control are Tephritidae (peacock flies) whose larvae feed on Centaurea. Knapweed peacock fly (Chaetorellia acrolophi) larvae eat spotted knapweed and some other species. The yellow starthistle peacock fly (C. australis) has an initial generation each year which often uses cornflower (C. cyanus) as larval food; later generations switch to yellow starthistle. The flies are generally considered less efficient in destroying the growing seedheads than the weevils, but may be superior under certain conditions; employing flies and weevils in combination is expensive and does not noticeably increase their effect.

 

Use by humans

Although the genus may be considered by a quite significant number of relatively informed individuals to have an overall negative impact on human interests, particularly agricultural interests, the situation is not straightforward enough to simply declare the genus, or, at least, its most aggressively-spreading species, altogether negative. For instance, due to their moderate to high nectar production, which can occur over a comparatively long duration, many species of Centaurea are popular food sources for insects that may otherwise attack certain crops.[citation needed] It may be advisable for some types of farms to allow certain species in this genus, such as cornflower (C. cyanus) in a European setting, to grow adjacent to fields. Although they support and attract many types of beneficial life (not just beetles), these areas are known as beetle banks. When they are present, some pests may be drawn away from crops to them and predatory insects and arachnids that feed upon pest insects will be better-supported by these more naturalized areas. They additionally have the beneficial aspect of supporting pollinators, unlike many field crops such as maize. Moreover, being untreated with pesticides and providing more diversity, plants growing in more wild areas adjacent to farms produce more insects that attract and support birds which can also feed on pests that would harm crops. Insect production is especially high for beetle banks that have enough plants that serve in the role of host plant for immature insects, rather than just in the roles of adult food and/or shelter provision.

 

Some plants which are considered invasive or problematic in certain areas can have beneficial qualities that outweigh their negative qualities from a human and/or human agricultural point of view, although this sometimes requires some human management – particularly if adequate biological control has not been established for the more aggressive species. An example is wild parsnip, Pastinaca sativa, which produces florets that feed predatory (and other beneficial) insects as well as large tubular stems that provide winter shelter for native bees, wasps, and other organisms that can be beneficial for agriculture. The plant is considered invasive in some areas of the United States and is also often considered undesirable due to its ability to cause contact skin irritation. However, it also serves as a host plant for the black swallowtail butterfly, helps to bring nutrients up from soils with its deep taproot, and possesses evergreen foliage even in climate zones such as US zone 6. This foliage increases soil warmth and moisture which can be beneficial for certain types of life. Perhaps the most dramatic example of a generally disliked plant's beneficial qualities being usually overlooked is the often-despised ragwort, Jacobaea vulgaris, which topped the list by a large amount for nectar production in a UK study, with a production per floral unit of (2921 ± 448μg). This very high nectar production, coupled with its early blooming period, makes the plant helpful for the establishment of bee colonies in spring — a period that is often not well-served by commercial flower meadow seed mixes. It also has the situationally-beneficial quality of being a spring ephemeral, as well as an annual that lacks difficult-to-combat roots. Plants that provide necessary structural supports for invertebrate and small vertebrate predators can help to keep overall pest populations low.

 

The abundant nectar produced by C. solstitialis flowers attracts many pollinators. This is another reason for the success of the (situationally) highly invasive species. Due to genetic differences related to evolutionary adaption, not all members of Centaurea produce the same amount of nectar. Growing conditions, such as climate and soil, can have a very strong impact, even if the plants grow and flower. For instance, cornflower plants, Centaurea cyanus, produced 33% less seasonal nectar than Centaurea nigra in a UK study. C. nigra also ranked higher than ragwort in another UK study, although ragwort was still in the top 10 for yearly nectar production. The strong nectar production of certain members of the genus can be exploited to the farmer's advantage, possibly in combination with biological control. In particular, the yellow starthistle (C. solstitialis) as well as spotted knapweed (C. maculosa) are major honey plants for beekeepers. Monofloral honey from these plants is light and slightly tangy, and one of the finest honeys produced in the United States – due to its better availability, it is even fraudulently relabeled and sold as the scarce and expensive sourwood honey of the Appalachian Mountains. Placing beehives near stands of Centaurea will cause increased pollination. As most seedheads fail however when biocontrol pests have established themselves, the plants will bloom ever more abundantly in an attempt to replace the destroyed seedheads, to the point where they exhaust their resources in providing food for the pests (seeds), bees (pollen) and humans (honey). Output of allelopathic compounds is also liable to be reduced under such conditions – the plant has to compromise between allocating energy to reproduction and defense. This renders the weeds more likely to be suppressed by native vegetation or crops in the following years, especially if properly timed controlled burning[5] and/or targeted grazing by suitable livestock are also employed. While yellow starthistle and perhaps other species are toxic to equines, some other livestock may eat the non-spiny knapweeds with relish. In Europe, common knapweed (C. nigra) and globe knapweed (C. macrocephala) are locally important pollen sources for honeybees in mid-late summer.

 

8-Hydroxyquinoline has been identified as a main allelopathic compound produced by diffuse knapweed (C. diffusa); native North American plants are typically sensitive to it, while those of Eastern Europe and Asia Minor usually have coevolved with the knapweed and are little harmed if at all, aided by native microorganisms that break down or even feed on the abundantly secreted compound. Thus, 8-hydroxyquinoline is potentially useful to control American plants that have become invasive weeds in the diffuse knapweed's native range.

 

Arctiin, found in C. imperialis, has shown anticancer activity in laboratory studies. The roots of the long-lost C. foliosa, an endemic of Hatay Province (Turkey), are used in folk medicine, and other species are presumably too. A South Italian variety[verification needed] of the purple starthistle (C. calcitrapa) is traditionally consumed by ethnic Albanians (Arbëreshë people) in the Vulture area (southern Italy); e.g. in the Arbëreshë communities in Lucania the young whorls of C. calcitrapa are boiled and fried in mixtures with other weedy non-cultivated greens. According to research by the Michael Heinrich group at the Centre for Pharmacognosy and Phytotherapy (School of Pharmacy, University of London) "the antioxidant activity [...] of the young whorls of Centaurea calcitrapa, both in the DPPH and in the lipid peroxidation inhibition assays, [is] very interesting and [the] species should be investigated phytochemically and biochemically focusing on these properties". Extracts from C. calcitrapa were furthermore found to have significant xanthine oxidase (XO)-inhibiting activity.

 

Spotted knapweed as well as other species are rich in cnicin, a bitter compound found mainly in the leaves and often used to flavor the digestif amaro. In western Crete, Greece a local variety[verification needed] of C. calcitrapa called gourounaki (γουρουνάκι "little pig") also has its leaves eaten boiled by the locals. In the same island an endemic local species, C. idaea called katsoula (κατσούλα), tsita (τσίτα) or aspragatha (ασπραγκάθα), has its leaves eaten boiled by the locals too.

 

Some species are cultivated as ornamental plants in gardens. As regards other aspects of popular culture, cornflower (C. cyanus) is the floral emblem of Östergötland province (Sweden) – where is it called blåklint, literally "blue mountain" – and of Päijänne Tavastia region in Finland, where it is known as ruiskaunokki ("rye-beaks") or ruiskukka ("rye-flower"). It is also the national flower of Estonia where its local name rukkilill means "rye-lily", Belarus where it is called vałoška (Belarusian: валошка), and one of those of Germany where it is called Kornblume ("cornflower"). The origin of the name "caltrop" for the ancient low-tech area denial weapon is probably in some way connected with C. calcitrapa and its spiny seeds. This plant is attested to by the colloquial name "caltrop" at a time when the weapons were still called by their Roman name tribulus. Lastly, the color cornflower blue is named after C. cyanus. Cornflower is also used as a cut flower.

 

As namesake member of the subtribe Centaureinae of tribe Cardueae, the knapweeds are probably most closely related to genera such as Carthamus (distaff thistles), Cnicus (blessed thistle), Crupina (crupinas) or Notobasis (Syrian thistle), and somewhat less closely to most other thistles. The monotypic Cnicus seems in fact to properly belong in Centaurea.

 

Research in the late 20th century shows that Centaurea as traditionally defined is polyphyletic. A number of 19th- and 20th-century efforts to reorganize the genus were not successful, and it is not yet clear what the consequences of the recent research will be for classification of this genus and other related genera. The type species C. centaurium stands somewhat apart from the main lineage of knapweeds and thus the taxonomic consequences of a rearrangement might be severe, with hundreds of species needing to be moved to new genera. It has thus been proposed to change the type species to one of the main lineages to avoid this problem. What seems certain however is that the basketflowers – presently treated as a section Plectocephalus – will be reinstated as a distinct genus in the near future. The rock-centauries (Cheirolophus), formerly usually included in Centaurea, are now already treated as separate genus.

 

Better-known Centaurea species include:

 

Centaurea acaulis

Centaurea adpressa

Centaurea aegyptiaca

Centaurea aeolica

Centaurea aggregata

Centaurea akamantis – Akamas centaurea

Centaurea alba

Centaurea albonitens Turrill

Centaurea alpestris

Centaurea alpina

Centaurea ambigua

Centaurea amblyolepis

Centaurea americana – American basketflower, American starthistle

Centaurea ammocyanus

Centaurea antennata Dufour

Centaurea antiochia Boiss.

Centaurea aplolepa

Centaurea aplolepa subsp. carueliana

Centaurea appendicigera C.Koch

Centaurea argentea

Centaurea ascalonica

Centaurea aspera L. – rough starthistle

Centaurea atacamensis (Reiche) I.M.Johnst.

Centaurea atropurpurea

Centaurea ×aurata

Centaurea babylonica L.

Centaurea balsamita

Centaurea behen L. – ak behmen (Turkish)

Centaurea bella

Centaurea benedicta – Cnicus

Centaurea bieberseinii

Centaurea borjae

Centaurea bovina

Centaurea bracteata

Centaurea brevifimbriata Hub.-Mor.

Centaurea bulbosa

Centaurea busambarensis Guss.

Centaurea cachinalensis

Centaurea calcitrapa – purple starthistle, red starthistle, "caltrop"

Centaurea calcitrapoides

Centaurea cariensis Boiss.

Centaurea cariensiformis Hub.-Mor.

Centaurea caroli-henrici Gabrieljan & Dittrich

Centaurea centaurium L.

Centaurea chilensis

Centaurea cineraria – velvet centaurea, dusty miller

Centaurea clementei

Centaurea collina L.

Centaurea corymbosa

Centaurea crithmifolia

Centaurea crocodylium

Centaurea cyanoides J.Berggr. & Wahlenb.

Centaurea cyanus – cornflower, bachelor's button, boutonniere flower, hurtsickle, bluebottle, basketflower

Centaurea damascena

Centaurea debeauxii Gren. & Godr.

Centaurea demirizii Wagenitz

Centaurea depressa – low cornflower

Centaurea deusta

Centaurea diffusa – diffuse knapweed, white knapweed, tumble knapweed

Centaurea diluta – North African knapweed

Centaurea drabifolia Sm.

Centaurea drabifolioides Hub.-Mor.

Centaurea dschungarica

Centaurea emilae Hüseynova et Qaraxani[13]

Centaurea eriophora

Centaurea eryngioides

Centaurea filiformis

Centaurea fischeri Willd.

Centaurea floccosa

Centaurea foliosa Boiss. & Kotschy

Centaurea forojuliensis

Centaurea friderici Vis. – palagruška zečina (Croatian)

Centaurea gayana

Centaurea glaberrima Tausch

Centaurea glastifolia

Centaurea grinensis

Centaurea gymnocarpa

Centaurea haradjianii Wagenitz

Centaurea hedgei

Centaurea helenioides Boiss.

Centaurea hermannii F.Hermann

Centaurea horrida Badarò – fiordaliso spinoso (Italian)

Centaurea hyalolepis

Centaurea hypoleuca

Centaurea iberica – Iberian starthistle, Iberian knapweed

Centaurea idaea – katsoula, tsita (Cretan Greek)

Centaurea imperialis Hausskn. ex Bornm.

Centaurea jabukensis

Centaurea jacea – brown knapweed, brownray knapweed

Centaurea kasakorum

Centaurea kopetaghensis

Centaurea kotschyana Heuff.

Centaurea lanulata

Centaurea leptophylla

Centaurea leucophylla

Centaurea limbata

Centaurea lydia Boiss.

Centaurea macrocephala Puschk. ex Willd. – globe knapweed, Armenian basketflower

Centaurea maculosa – spotted knapweed (might belong in C. stoebe subsp. micranthos)

Centaurea mannagettae

Centaurea margaritalba Klok.

Centaurea marschalliana

Centaurea melitensis – Maltese starthistle; tocalote, tocolote (California)

Centaurea minor

Centaurea moschata – sweet sultan

Centaurea ×moncktonii C.E.Britton – meadow knapweed, protean knapweed (= C. ×pratensis Thuill non Salisb.)

Centaurea monocephala

Centaurea montana – montane knapweed, perennial cornflower, mountain cornflower, mountain bluet

Centaurea napifolia L. – fiordaliso romano (Italian)

Centaurea nervosa Rchb. ex Steud.

Centaurea nigra – common knapweed, black knapweed, lesser knapweed, hardheads

Centaurea nigrescens – Tyrol knapweed, short-fringed knapweed, Tyrol thistle

Centaurea nigrifimbria (C.Koch) Sosn.

Centaurea nivea (Bornm.) Wagenitz

Centaurea onopordifolia

Centaurea orientalis L.

Centaurea ornata Willd.

Centaurea ovina

Centaurea pallescens Delile

Centaurea paniculata L.

Centaurea parlatoris

Centaurea pecho

Centaurea phrygia – wig knapweed

Centaurea pindicola

Centaurea polypodiifolia

Centaurea ×pratensis Salisb. (C. jacea × C. nigra) – meadow knapweed

Centaurea procurrens

Centaurea ×psammogena G.Gayer. (C. diffusa × C. stoebe subsp. micranthos)

Centaurea pseudocaerulescens

Centaurea pseudophrygia C.A.Mey.

Centaurea pulcherrima Willd.

Centaurea pullata L.

Centaurea pumilio

Centaurea ragusina L.

Centaurea rigida

Centaurea rothrockii Greenm. – Mexican basketflower, Rothrock's basketflower, Rothrock's knapweed

Centaurea ruthenica

Centaurea rutifolia Sm.

Centaurea sadleriana – Pannonian knapweed

Centaurea salicifolia Bieb. ex Willd.

Centaurea scabiosa – greater knapweed

Centaurea scannensis

Centaurea scoparia

Centaurea scopulorum Boiss. & Heldr.

Centaurea seguenzae

Centaurea seridis L.

Centaurea sibirica

Centaurea simplicicaulis

Centaurea sinaica

Centaurea solstitialis – yellow starthistle, golden starthistle, yellow cockspur, St. Barnaby's thistle, Barnaby thistle

Centaurea speciosa

Centaurea sphaerocephala L.

Centaurea stenolepis

Centaurea stoebe L.

Centaurea stoebe subsp. micranthos (Gugler) Hayek

Centaurea straminicephala

Centaurea sulphurea – Sicilian starthistle

Centaurea tauromenitana Guss.

Centaurea tenoreana

Centaurea tommasinii

Centaurea transalpina Schleich. ex DC.

Centaurea tchihatcheffii — yanardöner (Turkish)

Centaurea trichocephala Bieb. ex Willd. – featherhead knapweed

Centaurea triniifolia

Centaurea triumfettii All.

Centaurea ucriae Lacaita

Centaurea uniflora Turra

Centaurea verbascifolia Vahl

Centaurea verutum L.

Centaurea virgata

Centaurea virgata subsp. squarrosa – squarrose knapweed

Centaurea wiedemanniana Fisch. & Mey.

Centaurea yozgatensis Wagenitz

Formerly placed here

Plant species placed in Centaurea in former times include:

 

Acroptilon repens – Russian knapweed (as C. repens)

Cheirolophus crassifolius – Maltese rock-centaury (as C. crassifolia, C. spathulata)

Femeniasia balearica (as C. balearica)

Volutaria muricata (as C. muricata)

Native, cool season, annual, small, tufted annual herb 2-11 cm tall. Leaves are linear, innermost ones usually reduced to a short membranous hairless sheath. Stems are erect, unbranched and leafless. Flowerheads are terminal cymose heads enclosed by 2 primary bracts with dilated bases; each bract encloses 1–numerous pseudanthia; pseudanthia each consist of 1–30 ± fused female flowers superimposed in 1 or 2 rows, styles usually fused at base, usually with 1 male flower at base; secondary bracts 2 or 3 per pseudanthium. Flowering is in spring. Grows in heath, scrub, mallee, woodland and sclerophyll forest on sand or infertile soils; mostly east and north of the A.C.T., but this one was in Albury.

Native, cool season, annual, small, tufted annual herb 2-11 cm tall. Leaves are linear, innermost ones usually reduced to a short membranous hairless sheath. Stems are erect, unbranched and leafless. Flowerheads are terminal cymose heads enclosed by 2 primary bracts with dilated bases; each bract encloses 1–numerous pseudanthia; pseudanthia each consist of 1–30 ± fused female flowers superimposed in 1 or 2 rows, styles usually fused at base, usually with 1 male flower at base; secondary bracts 2 or 3 per pseudanthium. Flowering is in spring. Grows in heath, scrub, mallee, woodland and sclerophyll forest on sand or infertile soils; mostly east and north of the A.C.T., but this one was in Albury.

Several groups of Euphorbia around the grounds of Dix's field in Exeter, UK. ===Information=== Euphorbia is a very large and diverse genus of flowering plants, commonly called spurge, in the spurge family (Euphorbiaceae). "Euphorbia" is sometimes used in ordinary English to collectively refer to all members of Euphorbiaceae (in deference to the type genus), not just to members of the genus. Some euphorbias are commercially widely available, such as poinsettias at Christmas. Some are commonly cultivated as ornamentals, or collected and highly valued for the aesthetic appearance of their unique floral structures, such as the crown of thorns plant (Euphorbia milii). Euphorbias from the deserts of Southern Africa and Madagascar have evolved physical characteristics and forms similar to cacti of North and South America, so they (along with various other kinds of plants) are often incorrectly referred to as "cacti". Some are used as ornamentals in landscaping, because of beautiful or striking overall forms, and drought and heat tolerance. Euphorbias range from tiny annual plants to large and long-lived trees. The genus has over or about 2,000 members, making it one of the largest genera of flowering plants. It also has one of the largest ranges of chromosome counts, along with Rumex and Senecio. The plants share the feature of having a poisonous, milky, white, latex-like sap, and unusual and unique floral structures. The genus may be described by properties of its members' gene sequences, or by the shape and form (morphology) of its heads of flowers. When viewed as a whole, the head of flowers looks like a single flower (a pseudanthium). It has a unique kind of pseudanthium, called a cyathium, where each flower in the head is reduced to its barest essential part needed for sexual reproduction. The individual flowers are either male or female, with the male flowers reduced to only the stamen, and the females to the pistil. These flowers have no sepals, petals, or other parts that are typical of flowers in other kinds of plants. Structures supporting the flower head and beneath have evolved to attract pollinators with nectar, and with shapes and colours that function the way petals and other flower parts do in other flowers. It is the only genus of plants that has all three kinds of photosynthesis, CAM, C3, and C4. The genus can be found all over the world. The forms range from annual plants laying on the ground, to well-developed tall trees. In deserts in Madagascar and southern Africa, convergent evolution has led to cactus-like forms where the plants occupy the same ecological niche as cacti do in deserts of North and South America. The genus is primarily found in the tropical and subtropical regions of Africa and the Americas, but also in temperate zones worldwide. ===Other names=== Spurge ===Useful links=== ift.tt/1Pf8Eml ift.tt/2h4Wpls ift.tt/2oqjgK9 *Details sourced from the above links ===Scientific classification=== Kingdom: Plantae Clade: Angiosperms Clade: Eudicots Clade: Rosids Order: Malpighiales Family: Euphorbiaceae Tribe: Euphorbieae Subtribe: Euphorbiinae Griseb. Genus: Euphorbia

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographys by Lauren Ruth

Native, cool season, annual, small, tufted annual herb 2-11 cm tall. Leaves are linear, innermost ones usually reduced to a short membranous hairless sheath. Stems are erect, unbranched and leafless. Flowerheads are terminal cymose heads enclosed by 2 primary bracts with dilated bases; each bract encloses 1–numerous pseudanthia; pseudanthia each consist of 1–30 ± fused female flowers superimposed in 1 or 2 rows, styles usually fused at base, usually with 1 male flower at base; secondary bracts 2 or 3 per pseudanthium. Flowering is in spring. Grows in heath, scrub, mallee, woodland and sclerophyll forest on sand or infertile soils; mostly east and north of the A.C.T., but this one was in Albury.

Pseudanthium

Madia exigua on Lumpkin Ridge, northern Sierra Nevada, California, 27 May 2009.

Native, cool season, annual, small, tufted annual herb 2-11 cm tall. Leaves are linear, innermost ones usually reduced to a short membranous hairless sheath. Stems are erect, unbranched and leafless. Flowerheads are terminal cymose heads enclosed by 2 primary bracts with dilated bases; each bract encloses 1–numerous pseudanthia; pseudanthia each consist of 1–30 ± fused female flowers superimposed in 1 or 2 rows, styles usually fused at base, usually with 1 male flower at base; secondary bracts 2 or 3 per pseudanthium. Flowering is in spring. Grows in heath, scrub, mallee, woodland and sclerophyll forest on sand or infertile soils; mostly east and north of the A.C.T., but this one was in Albury.

Several groups of Euphorbia around the grounds of Dix's field in Exeter, UK. ===Information=== Euphorbia is a very large and diverse genus of flowering plants, commonly called spurge, in the spurge family (Euphorbiaceae). "Euphorbia" is sometimes used in ordinary English to collectively refer to all members of Euphorbiaceae (in deference to the type genus), not just to members of the genus. Some euphorbias are commercially widely available, such as poinsettias at Christmas. Some are commonly cultivated as ornamentals, or collected and highly valued for the aesthetic appearance of their unique floral structures, such as the crown of thorns plant (Euphorbia milii). Euphorbias from the deserts of Southern Africa and Madagascar have evolved physical characteristics and forms similar to cacti of North and South America, so they (along with various other kinds of plants) are often incorrectly referred to as "cacti". Some are used as ornamentals in landscaping, because of beautiful or striking overall forms, and drought and heat tolerance. Euphorbias range from tiny annual plants to large and long-lived trees. The genus has over or about 2,000 members, making it one of the largest genera of flowering plants. It also has one of the largest ranges of chromosome counts, along with Rumex and Senecio. The plants share the feature of having a poisonous, milky, white, latex-like sap, and unusual and unique floral structures. The genus may be described by properties of its members' gene sequences, or by the shape and form (morphology) of its heads of flowers. When viewed as a whole, the head of flowers looks like a single flower (a pseudanthium). It has a unique kind of pseudanthium, called a cyathium, where each flower in the head is reduced to its barest essential part needed for sexual reproduction. The individual flowers are either male or female, with the male flowers reduced to only the stamen, and the females to the pistil. These flowers have no sepals, petals, or other parts that are typical of flowers in other kinds of plants. Structures supporting the flower head and beneath have evolved to attract pollinators with nectar, and with shapes and colours that function the way petals and other flower parts do in other flowers. It is the only genus of plants that has all three kinds of photosynthesis, CAM, C3, and C4. The genus can be found all over the world. The forms range from annual plants laying on the ground, to well-developed tall trees. In deserts in Madagascar and southern Africa, convergent evolution has led to cactus-like forms where the plants occupy the same ecological niche as cacti do in deserts of North and South America. The genus is primarily found in the tropical and subtropical regions of Africa and the Americas, but also in temperate zones worldwide. ===Other names=== Spurge ===Useful links=== ift.tt/1Pf8Eml ift.tt/2h4Wpls ift.tt/2oqjgK9 *Details sourced from the above links ===Scientific classification=== Kingdom: Plantae Clade: Angiosperms Clade: Eudicots Clade: Rosids Order: Malpighiales Family: Euphorbiaceae Tribe: Euphorbieae Subtribe: Euphorbiinae Griseb. Genus: Euphorbia

Madia exigua on Lumpkin Ridge, northern Sierra Nevada, California, 27 May 2009.

*** Arctic Islands 2017 Expedition (polarforskningsportalen.se/en/arctic/expeditions/arktiska...) ***

Several groups of Euphorbia around the grounds of Dix's field in Exeter, UK. ===Information=== Euphorbia is a very large and diverse genus of flowering plants, commonly called spurge, in the spurge family (Euphorbiaceae). "Euphorbia" is sometimes used in ordinary English to collectively refer to all members of Euphorbiaceae (in deference to the type genus), not just to members of the genus. Some euphorbias are commercially widely available, such as poinsettias at Christmas. Some are commonly cultivated as ornamentals, or collected and highly valued for the aesthetic appearance of their unique floral structures, such as the crown of thorns plant (Euphorbia milii). Euphorbias from the deserts of Southern Africa and Madagascar have evolved physical characteristics and forms similar to cacti of North and South America, so they (along with various other kinds of plants) are often incorrectly referred to as "cacti". Some are used as ornamentals in landscaping, because of beautiful or striking overall forms, and drought and heat tolerance. Euphorbias range from tiny annual plants to large and long-lived trees. The genus has over or about 2,000 members, making it one of the largest genera of flowering plants. It also has one of the largest ranges of chromosome counts, along with Rumex and Senecio. The plants share the feature of having a poisonous, milky, white, latex-like sap, and unusual and unique floral structures. The genus may be described by properties of its members' gene sequences, or by the shape and form (morphology) of its heads of flowers. When viewed as a whole, the head of flowers looks like a single flower (a pseudanthium). It has a unique kind of pseudanthium, called a cyathium, where each flower in the head is reduced to its barest essential part needed for sexual reproduction. The individual flowers are either male or female, with the male flowers reduced to only the stamen, and the females to the pistil. These flowers have no sepals, petals, or other parts that are typical of flowers in other kinds of plants. Structures supporting the flower head and beneath have evolved to attract pollinators with nectar, and with shapes and colours that function the way petals and other flower parts do in other flowers. It is the only genus of plants that has all three kinds of photosynthesis, CAM, C3, and C4. The genus can be found all over the world. The forms range from annual plants laying on the ground, to well-developed tall trees. In deserts in Madagascar and southern Africa, convergent evolution has led to cactus-like forms where the plants occupy the same ecological niche as cacti do in deserts of North and South America. The genus is primarily found in the tropical and subtropical regions of Africa and the Americas, but also in temperate zones worldwide. ===Other names=== Spurge ===Useful links=== ift.tt/1Pf8Eml ift.tt/2h4Wpls ift.tt/2oqjgK9 *Details sourced from the above links ===Scientific classification=== Kingdom: Plantae Clade: Angiosperms Clade: Eudicots Clade: Rosids Order: Malpighiales Family: Euphorbiaceae Tribe: Euphorbieae Subtribe: Euphorbiinae Griseb. Genus: Euphorbia

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographs by Lauren Ruth

Several groups of Euphorbia around the grounds of Dix's field in Exeter, UK. ===Information=== Euphorbia is a very large and diverse genus of flowering plants, commonly called spurge, in the spurge family (Euphorbiaceae). "Euphorbia" is sometimes used in ordinary English to collectively refer to all members of Euphorbiaceae (in deference to the type genus), not just to members of the genus. Some euphorbias are commercially widely available, such as poinsettias at Christmas. Some are commonly cultivated as ornamentals, or collected and highly valued for the aesthetic appearance of their unique floral structures, such as the crown of thorns plant (Euphorbia milii). Euphorbias from the deserts of Southern Africa and Madagascar have evolved physical characteristics and forms similar to cacti of North and South America, so they (along with various other kinds of plants) are often incorrectly referred to as "cacti". Some are used as ornamentals in landscaping, because of beautiful or striking overall forms, and drought and heat tolerance. Euphorbias range from tiny annual plants to large and long-lived trees. The genus has over or about 2,000 members, making it one of the largest genera of flowering plants. It also has one of the largest ranges of chromosome counts, along with Rumex and Senecio. The plants share the feature of having a poisonous, milky, white, latex-like sap, and unusual and unique floral structures. The genus may be described by properties of its members' gene sequences, or by the shape and form (morphology) of its heads of flowers. When viewed as a whole, the head of flowers looks like a single flower (a pseudanthium). It has a unique kind of pseudanthium, called a cyathium, where each flower in the head is reduced to its barest essential part needed for sexual reproduction. The individual flowers are either male or female, with the male flowers reduced to only the stamen, and the females to the pistil. These flowers have no sepals, petals, or other parts that are typical of flowers in other kinds of plants. Structures supporting the flower head and beneath have evolved to attract pollinators with nectar, and with shapes and colours that function the way petals and other flower parts do in other flowers. It is the only genus of plants that has all three kinds of photosynthesis, CAM, C3, and C4. The genus can be found all over the world. The forms range from annual plants laying on the ground, to well-developed tall trees. In deserts in Madagascar and southern Africa, convergent evolution has led to cactus-like forms where the plants occupy the same ecological niche as cacti do in deserts of North and South America. The genus is primarily found in the tropical and subtropical regions of Africa and the Americas, but also in temperate zones worldwide. ===Other names=== Spurge ===Useful links=== ift.tt/1Pf8Eml ift.tt/2h4Wpls ift.tt/2oqjgK9 *Details sourced from the above links ===Scientific classification=== Kingdom: Plantae Clade: Angiosperms Clade: Eudicots Clade: Rosids Order: Malpighiales Family: Euphorbiaceae Tribe: Euphorbieae Subtribe: Euphorbiinae Griseb. Genus: Euphorbia

*** Arctic Islands 2017 Expedition (polarforskningsportalen.se/en/arctic/expeditions/arktiska...) ***

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographs by Lauren Ruth

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographs by Lauren Ruth

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographs by Lauren Ruth

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographs by Lauren Ruth

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographs by Lauren Ruth

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographs by Lauren Ruth

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographs by Lauren Ruth

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographs by Lauren Ruth

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographs by Lauren Ruth

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographs by Lauren Ruth

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographs by Lauren Ruth

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographs by Lauren Ruth

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographs by Lauren Ruth

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographs by Lauren Ruth

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographs by Lauren Ruth

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographs by Lauren Ruth

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographs by Lauren Ruth

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographs by Lauren Ruth

cultivated, Hillsborough, North Carolina, USA.

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographs by Lauren Ruth

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographs by Lauren Ruth

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographs by Lauren Ruth

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographs by Lauren Ruth

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographs by Lauren Ruth

A collaborative work by Soo Sunny Park & Lauren Ruth

Tiltfactor Laboratory

PLAYCUBE mobile exhibition space

Photographs by Lauren Ruth