Acacia

About 1,300; see List of Acacia species

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Acacia is a genus of shrubs and trees of Gondwanian origin belonging to the subfamily Mimosoideae of the Pea Family Fabaceae, first described from Africa by Linnaeus in 1773.

Related Topics:
Shrub - Tree - Gondwanian - Mimosoideae - Fabaceae - Linnaeus - 1773

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There are roughly 1300 species worldwide: about 950 of them being native to Australia, while the remainder are spread around the dry tropical to warm-temperate regions of both hemispheres, including Africa, southern Asia, and the Americas. The genus Acacia however is not monophyletic. This has led to the breaking up of this genus in 5 new genera. This has been discussed in List of Acacia species.

Related Topics:
Australia - Monophyletic - List of Acacia species

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The northernmost species is Acacia greggii (Catclaw Acacia), reaching 37°10' N in southern Utah in the United States; the southernmost are Acacia dealbata (Silver Wattle), Acacia longifolia (Coast Wattle or Sydney Golden Wattle), Acacia mearnsii (Black Wattle), and Acacia melanoxylon (Blackwood), reaching 43°30' S in Tasmania, Australia, while Acacia caven (Espinillo Negro) reaches nearly as far south in northeastern Chubut Province, Argentina. Australian species are usually called wattles, while African and American species tend to be known as acacias.

Related Topics:
Catclaw Acacia - Utah - United States - Silver Wattle - Coast Wattle - Black Wattle - Blackwood - Tasmania - Espinillo Negro - Chubut Province - Argentina - Wattle

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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.

Related Topics:
Petiole - Phyllode - Acacia glaucoptera - Cladode

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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 (as in Acacia purpureapetala) or red (in the recently grown cultivar Acacia leprosa 'Scarlet Blaze).

Related Topics:
Flower - Acacia purpureapetala - Acacia leprosa

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The plants often bear spines, especially those 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, Acacia giraffae, the Camelthorn of Africa. In the Central American Acacia sphaerocephala (Bullthorn Acacia) and Acacia spadicigera, the large thorn-like stipules are hollow and afford shelter for ants, which feed on a secretion of honey on the leaf-stalk and curious food-bodies at the tips of the leaflets; in return they protect the plant against leaf-eating insects.

Related Topics:
Kangaroo-thorn - Camelthorn - Bullthorn Acacia - Acacia spadicigera - Ant

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In common parlance the term "acacia" is occasionally misapplied to species of the genus Robinia, which also belongs in the pea family, although placed in a different subgenus. Robinia pseudoacacia, an American species normally known as Black locust, is sometimes called "false acacia" in cultivation in Britain.

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