Acacia
Lifespan: | ⌛ | perennial |
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Features: | ✓ | evergreen, deciduous |
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Fabaceae > |
Acacia > |
Acacia (pronounced /əˈkeɪʃə/) is a genus of shrubs and trees belonging to the family Fabaceae. Acacias are also known as thorntrees, whistling thorns or wattles, including the yellow-fever acacia and umbrella acacias.
Until 2005, there were thought to be roughly 1300 species of acacia worldwide, about 960 of them native to Australia, with the remainder spread around the tropical to warm-temperate regions of both hemispheres, including Europe, Africa, southern Asia, and the Americas. However, the genus was then divided into five, with the name Acacia retained for the Australian species, and most of the species outside Australia divided into Vachellia and Senegalia.
Acacias are also known as thorntrees or wattles, including the yellow-fever acacia and umbrella acacias.
A few species are widely grown as ornamentals in gardens; the most popular perhaps is Acacia dealbata (Silver Wattle), with its attractive glaucous to silvery leaves and bright yellow flowers; it is erroneously known as "mimosa" in some areas where it is cultivated, through confusion with the related genus Mimosa.
The leaves of acacias are compound pinnate in general. In some species, however, more especially in the Australian and Pacific islands species, the leaflets are suppressed, and the leaf-stalks (petioles) become vertically flattened, and serve the purpose of leaves. These are known as phyllodes. The vertical orientation of the phyllodes protects them from intense sunlight, as with their edges towards the sky and earth they do not intercept light so fully as horizontally placed leaves. A few species (such as Acacia glaucoptera) lack leaves or phyllodes altogether, but possess instead cladodes, modified leaf-like photosynthetic stems functioning as leaves.
The small flowers have five very small petals, almost hidden by the long stamens, and are arranged in dense globular or cylindrical clusters; they are yellow or cream-colored in most species, whitish in some, even purple (Acacia purpureapetala) or red (Acacia leprosa Scarlet Blaze). Acacia flowers can be distinguished from those of a large related genus, Albizia, by their stamens which are not joined at the base. Also, unlike individual Mimosa flowers, those of Acacia have more than 10 stamens..[1]
The plants often bear spines, especially those species growing in arid regions. These sometimes represent branches which have become short, hard and pungent, or sometimes leaf-stipules. Acacia armata is the Kangaroo-thorn of Australia and Acacia erioloba is the Camelthorn of Africa.
ExpandRead about Acacia in the Standard Cyclopedia of Horticulture
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Cultivation
ExpandRead about Acacia in the Standard Cyclopedia of Horticulture
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Propagation
Acacia seeds can be difficult to germinate. Research has found that immersing the seeds in various temperatures (usually around 80 °C) and manual seed coat chipping can improve yields to approximately 80 percent.[2]
ExpandRead about Acacia in the Standard Cyclopedia of Horticulture
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Pests and diseases
In Australia, Acacia species are sometimes used as food plants by the larvae of hepialid moths of the genus Aenetus including A. ligniveren. These burrow horizontally into the trunk then vertically down. Other Lepidoptera larvae which have been recorded feeding on Acacia include Brown-tail, Endoclita malabaricus and Turnip Moth. The leaf-mining larvae of some bucculatricid moths also feed on Acacia: Bucculatrix agilis feeds exclusively on Acacia horrida and Bucculatrix flexuosa feeds exclusively on Acacia nilotica.
Species
There are over 1,300 species of Acacia. See List of Acacia species for a complete listing. The genus however is apparently not monophyletic. This discovery has led to the breaking up of Acacia into five new genera as discussed in list of Acacia species.
Gallery
References
External links
- w:Acacia. Some of the material on this page may be from Wikipedia, under the Creative Commons license.
- Acacia QR Code (Size 50, 100, 200, 500)
- ↑ Singh, Gurcharan (2004). Plant Systematics: An Integrated Approach. Science Publishers. pp. 445. ISBN 1578083516. http://books.google.com/books?id=In_Lv8iMt24C.
- ↑ J Clemens, PG Jones, NH Gilbert (1977). "Effect of seed treatments on germination in Acacia". Australian Journal of Botany 25 (3): 269-267. doi:10.1071/BT9770269. http://www.publish.csiro.au/nid/65/paper/BT9770269.htm.