Acacia, commonly known as wattles[ The genus name is Neo-Latin, borrowed from Koine Greek ἀκακία (akakia), a term used in antiquity to describe a preparation extracted from Vachellia nilotica, the original type species.
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Several species of Acacia have been introduced to various parts of the world, and two million hectares of commercial plantations have been established.
Description
Plants in the genus Acacia are shrubs or trees with bipinnate leaves, the mature leaves sometimes reduced to or rarely absent. There are 2 small at the base of the leaf, but sometimes fall off as the leaf matures. The flowers are borne in spikes or cylindrical heads, sometimes singly, in pairs or in racemes in the axils of leaves or phyllodes, sometimes in on the ends of branches. Each spike or cylindrical head has many small golden-yellow to pale creamy-white flowers, each with 4 or 5 and petals, more than 10 , and a thread-like style that is longer than the stamens. The fruit is a variably-shaped pod, sometimes flat or cylindrical, containing seeds with a fleshy aril on the end.
Taxonomy
The genus was first validly named in 1754 by Philip Miller in The Gardeners Dictionary.[ — only gives the name of the genus. Miller did not validly publish names of species in this book, as he did not consistently use binomial names.] In 1913 Nathaniel Lord Britton and Addison Brown selected Mimosa scorpioides (≡ Acacia scorpioides () = Acacia nilotica () ), a species from Africa, as the lectotype of the name.
Etymology
The genus name comes from Neo-Latin; Gaspard Bauhin in his book Pinax (1623) writes it coming from Dioscorides; the Koine term ἀκακία akakía is the name he uses for Vachellia nilotica, the original type species growing in Roman Egypt,
The origin of "wattle" may be an proto-Germanic word meaning "to weave".[
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History
The genus Acacia was considered to contain some leading to 1986. That year, Leslie Pedley questioned the monophyletic nature of the genus, and proposed a split into three genera: Acacia sensu stricto (161 species), Senegalia (231 species) and Racosperma (960 species), the last name first proposed in 1829 by Carl Friedrich Philipp von Martius as the name of a section in Acacia,[
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In the early 2000s, it had become evident that the genus was not monophyly and that several divergent lineages needed to be placed in separate genera. One lineage comprising over 900 species mainly native to Wallacea, Australia, New Guinea, and Indonesia was not closely related to the much smaller African lineage group containing the type species. This meant that the lineage, by far the most prolific in number of species, would need to be renamed. This caused controversy between South African and Australian botanists, who both claimed Acacia as a symbol of their respective nations and wished to retain the name for their respective branch.
Pedley's proposed name of Racosperma for this group had received little acclaim in the botanical community, especially by Australians. Australian botanists proposed a different solution, setting a different type species for Acacia, Acacia penninervis, allowing the largest number of species to remain in Acacia, resulting in the two pan-tropical lineages being renamed Vachellia and Senegalia, and the two endemic American lineages renamed Acaciella and Mariosousa.
In 2003, Anthony Orchard and Bruce Maslin filed a proposal to conserve the name Acacia with a different type, to retain the Australasian group of species in the genus Acacia.[
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The Australian species of the genus Paraserianthes s.l. ,namely P. Iophantha, are deemed its closest relatives.
Species
The names of more than 1,080 species of Acacia, mostly native to Australia, have been accepted by Plants of the World Online as of January 2025.
Fossil record
An Acacia-like long fossil seed pod has been described from the Eocene of the Paris Basin. (2025). 056509176X, Natural History Museum. 056509176X
Australia's oldest fossil Acacia pollen are recorded from the late Oligocene, 25 million years ago.
Distribution and habitat
Species of Acacia occurs in all Australian states and territories, and on its nearby islands. About 20 species occur naturally outside Australia and also occur in Australia. One species ( Acacia koa) is native to Hawaii
They are present in all terrestrial habitats, including alpine settings, rainforests, woodlands, grasslands, coastal dunes and deserts.[ In drier woodlands or forests they are an important component of the understory. Elsewhere they may be dominant, as in the Brigalow Belt, Myall woodlands and the eremaean Acacia aneura woodlands.][
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In Australia, Acacia forest is the second most common forest type after Eucalyptus forest, covering or 8% of total forest area. Acacia is also the nation's largest genus of flowering plants with almost found.
Ecology
Acacia is a common food source and host plant for butterflies of the genus Jalmenus. The imperial hairstreak, Jalmenus evagoras, feeds on at least 25 acacia species.
Acacia as an invasive species
South Africa
At least 16 Acacia species introduced to South Africa are categorised as invasive. In 1847, Acacia species were introduced to stabilise coastal dunes. In 1864 A. mearnsii was planted for its tannins; it has now become the most widespread invasive alien tree in South Africa.
Most are classified as highly invasive, Category 1a or 1b invaders. This means that most activities with regards to the species are prohibited (such as importing, propagating, introducing, translocating or trading) and it should be ensured that species exempted for an existing plantation does not spread beyond its domain.
Toxicity
Some species of acacia contain psychoactive alkaloids, and some contain potassium fluoroacetate.
Uses
The seed pods, flowers, and young leaves are generally edible either raw or cooked.
Aboriginal Australians have traditionally harvested the seeds of some species, to be ground into flour and eaten as a paste or baked into a cake. contain as much as 25% more protein than common cereals, and they store well for long periods due to the hard seed coats.[ A. melanoxylon (blackwood) and A. aneura (mulga) supply some of the most attractive timbers in the genus. Black wattle bark supported the tanning industries of several countries, and may supply tannins for production of waterproof .][
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In Vietnam, Acacia is used in plantations of non-native species that are regularly clear-cut for paper or timber uses.
Wattle bark collected in Australia in the 19th century was exported to Europe where it was used in the tanning process. One ton of wattle or mimosa bark contained about of pure tannin.
The gum of some species may be used as a substitute for gum arabic, known as Australian gum or wattle gum.
Cultivation
Some species of acacia – notably Acacia baileyana, Acacia dealbata and A. pravissima – are cultivated as ornamental garden plants. The 1889 publication Useful Native Plants of Australia describes various uses for eating.
External links
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— multi-access key for identifying Australian Acacias
