Sweet Acacia Overwhelming My Senses [Acacia farnesiana]

Morning Walk To The Sweet Acacia Tree

 

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* The species classification of this tree is in dispute. Some authorities maintain that the correct epithet is A. farnesiana and consider A. smallii and A. minuta to be synonyms. Other references describe A. minuta/A. smallii as sub-species of A. farnesiana.

 

ag.arizona.edu/pima/gardening/aridplants/Acacia_smallii.html

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Sweet Acacia (Acacia smallii) takes its common name from the unmistakable fragrance of its bright yellow ball flowers. It brings color, shade and a desert character to any landscape setting. Fragrant flowers, upright stature and rapid growth rate makes it desirable for commercial and residential landscapes. Popular as a theme tree in streetscape planting or at development entries it is probably used most often as individual accent trees in mixed desert planting or in small groupings.

 

Sweet Acacias like other desert natives have slender, white to gray thorns along the branches. These thorns are conspicuous, readily visible and pose little risk to pedestrians. They are frequently used in street and sidewalk plantings as well as in parking lots. Their abundant shade and moderate stature contributes to their use in courtyards, patios, seating areas and near building entries. If desired, thorns on lower branches are easily removed with hand pruners.

 

Mature trees are adapted to full sun, well draining soils and infrequent deep irrigation. They will thrive in both desert and lawn plantings. Much of the literature reports that trees mature to a height of 15' to 30' but some mature specimens in the Phoenix-metro area have reached 35' to 45' and may be 30' wide. Single and multiple trunked specimens are equally popular. Like most desert adapted species, multiple trunked and low branching specimens best capture the natural character of the tree and improves resistance to wind damage. These spreading, mature specimens maximize the flower display and the accompanying fragrance.

 

Leaves are made up of 10 to 20 pairs of tiny, dark green, oval leaflets giving the leaf canopy a delicate, fern-like appearance. Unpruned mature trees provide dense shade.

 

Sweet Acacias are semi-deciduous. In warmer winters or in certain protected microclimates trees may retain a majority of the leaf canopy. Remaining leaves are shed in spring with the resumption of growth and the development of new leaves.

 

Bloom periods are somewhat variable depending on the severity of winter temperatures and the inherent genetic variability found in this specie. In years with mild fall weather flower buds may appear December through February with blooms persisting into late winter and early spring. Other specimens may not begin blooming until mid to late spring and continue flowering into April and late May. Mature seed pods are dark brown, cylindrical, 2 to 2 1/2 long and 1/4 to 3/8" in diameter.

 

Acacia smallii appears hardy to about 15 to 20 degrees F. and survives most central and southern Arizona and southern California winters injury free.

 

Pruning and Shaping Sweet Acacias:

Pruning and shaping Sweet Acacias, especially during the first few years, is essential for establishing the form and structure of the mature tree. Because of their many desirable qualities (flowers, shade, dark green canopy) these trees are used in a wide array of landscape settings.

 

When designing this tree into the landscape appreciate that mature specimens will generally be as wide as they are tall and, with optimal growing conditions, can grow to 30 feet. Rapid tree growth coupled with the tendency to produce new branches all along the trunk make regular, moderate pruning a maintenance must. This succulent growth is ideally removed in the ½" to 3/4" diameter stage when it is easily cut with hand pruners or loppers.

 

Sweet Acacias possesses the best qualities of two other popular desert trees, Blue Palo Verde and Thornless Mesquites. It brings a brilliant floral display to the landscape, like those of Blue Palo Verde, in combination with a lush, deep green canopy, like Thornless Mesquite. With these qualities it is not surprising that it is among the most widely used desert trees.

 

Fostering the development of a more dispersed root system reduces the risk of wind throw. Arrange irrigation emitters at varying distances from the trunk to encourage roots to "seek out" water and nutrients. Irrigation emitter arrangement along with other information on irrigations practices for desert trees can be found at www.aridzonetrees.com and click on the FAQ link.

 

Seasonal Pruning:

Periodic thinning during the growing season is the most desirable method of pruning. Thin trees before the monsoon season to reduce wind damage to branches and uprooting of trees. Do not remove more than 30% of the canopy during the summer as this can lead to heavy flush growth and sunburn injuries that can later be invaded by wood boring insects. Avoid hedging or heading back desert species, as this will only stimulate excessive branching. For trees less than 7 years old, monthly light pruning (removal of no more than 20% to 30% of the leaf mass) during the growing season will keep the root to foliage mass ratio equal, not stimulate excessive flush growth, allow optimal photosynthesis to occur, initiate quicker root and tip branch growth, prevent sun burn injury and lessen the likelihood of wind damage. Always use clean, sharp tools that are regularly cleaned in a 10% solution of bleach. For detail pruning guide see www.aridzonetrees.com and click on the FAQ interactive button.

 

Insect Pests:

Periodically, insect pests can be a problem on some desert trees. On young trees, insect infestation can slow typical seasonal growth. Inspect trees during the growing season for common garden sucking insects such as aphids, thrip, whiteflies or psyllids. Spray applications of water or water and Safer Soap give short-term control (3 to 7 days) for small insect population.

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