''Acacia'', commonly known as wattles or acacias, is a genus of about of shrubs and trees in the subfamily Mimosoideae of the pea family

Fabaceae Fabaceae () or Leguminosae,International Code of Nomen ...

. Initially, it comprised a group of plant species native to Africa, South America, and

Australasia Australasia is a subregion of Oceania, comprising Australia, New Zealand (overlapping with Polynesia), and sometimes including New Guinea and surrounding islands (overlapping with Melanesia). The term is used in a number of different context ...

, but is now reserved for species mainly from Australia, with others from

New Guinea New Guinea (; Hiri Motu: ''Niu Gini''; , fossilized , also known as Papua or historically ) is the List of islands by area, world's second-largest island, with an area of . Located in Melanesia in the southwestern Pacific Ocean, the island is ...

, Southeast Asia, and the Indian Ocean. The genus name is

Neo-Latin Neo-LatinSidwell, Keith ''Classical Latin-Medieval Latin-Neo Latin'' in ; others, throughout. (also known as New Latin and Modern Latin) is the style of written Latin used in original literary, scholarly, and scientific works, first in Italy d ...

, borrowed from

Koine Greek Koine Greek (, ), also variously known as Hellenistic Greek, common Attic, the Alexandrian dialect, Biblical Greek, Septuagint Greek or New Testament Greek, was the koiné language, common supra-regional form of Greek language, Greek spoken and ...

(), a term used in antiquity to describe a preparation extracted from ''

Vachellia nilotica ''Vachellia nilotica'', more commonly known as ''Acacia nilotica'', and by the vernacular names of gum arabic tree, babul, thorn mimosa, Egyptian acacia or thorny acacia, is a flowering plant, flowering tree in the family Fabaceae. It is native t ...

'', the original

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

. 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

phyllode Phyllodes are modified petiole (botany), petioles or leaf stems, which are leaf-like in appearance and function. In some plants, these become flattened and widened, while the leaf itself becomes reduced or vanishes altogether. Thus the phyllode co ...

s or rarely absent. There are 2 small

stipule In botany, a stipule is an outgrowth typically borne on both sides (sometimes on just one side) of the base of a leafstalk (the petiole (botany), petiole). They are primarily found among dicots and rare among monocots. Stipules are considered part ...

s 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 A raceme () or racemoid is an unbranched, indeterminate type of inflorescence bearing flowers having short floral stalks along the shoots that bear the flowers. The oldest flowers grow close to the base and new flowers are produced as the shoo ...

in the axils of leaves or phyllodes, sometimes in

panicle In botany, a panicle is a much-branched inflorescence. (softcover ). Some authors distinguish it from a compound spike inflorescence, by requiring that the flowers (and fruit) be pedicellate (having a single stem per flower). The branches of a p ...

s 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

sepal A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106 Etymology The term ''sepalum'' ...

s and petals, more than 10

stamen The stamen (: stamina or stamens) is a part consisting of the male reproductive organs of a flower. Collectively, the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filament ...

s, and a thread-like

style Style, or styles may refer to: Film and television * ''Style'' (2001 film), a Hindi film starring Sharman Joshi, Riya Sen, Sahil Khan and Shilpi Mudgal * ''Style'' (2002 film), a Tamil drama film * ''Style'' (2004 film), a Burmese film * '' ...

that is longer than the stamens. The fruit is a variably-shaped pod, sometimes flat or cylindrical, containing seeds with a fleshy

aril An aril (), also called arillus, is a specialized outgrowth from a seed that partly or completely covers the seed. An arillode, or false aril, is sometimes distinguished: whereas an aril grows from the attachment point of the seed to the ova ...

on the end.

Taxonomy

The genus was first validly named in 1754 by

Philip Miller Philip Miller Royal Society, FRS (1691 – 18 December 1771) was an English botany, botanist and gardener of Scottish descent. Miller was chief gardener at the Chelsea Physic Garden for nearly 50 years from 1722, and wrote the highly popular ...

in '' The Gardeners Dictionary''. In 1913

Nathaniel Lord Britton Nathaniel Lord Britton (1859 – 1934) was an American botanist and taxonomist who co-founded the New York Botanical Garden in the Bronx, New York (state), New York. Early life Britton was born on the 15 of January 1859 at New Dorp, Staten Island ...

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

;

Gaspard Bauhin Gaspard Bauhin or Caspar Bauhin (; 17 January 1560 – 5 December 1624), was a Switzerland, Swiss botanist whose ''Pinax theatri botanici'' (1623) described thousands of plants and classified them in a manner that draws comparisons to the later ...

in his book ''Pinax'' (1623) writes it coming from

Dioscorides Pedanius Dioscorides (, ; 40–90 AD), "the father of pharmacognosy", was a Greek physician, pharmacologist, botanist, and author of (in the original , , both meaning "On Materia medica, Medical Material") , a 5-volume Greek encyclopedic phar ...

; the Koine term ''akakía'' is the name he uses for ''Vachellia nilotica'', the original

growing in

Roman Egypt Roman Egypt was an imperial province of the Roman Empire from 30 BC to AD 642. The province encompassed most of modern-day Egypt except for the Sinai. It was bordered by the provinces of Crete and Cyrenaica to the west and Judaea, ...

, from ''akakis'' meaning "point". The origin of " wattle" may be an

proto-Germanic Proto-Germanic (abbreviated PGmc; also called Common Germanic) is the linguistic reconstruction, reconstructed proto-language of the Germanic languages, Germanic branch of the Indo-European languages. Proto-Germanic eventually developed from ...

word meaning "to weave". First attested about 700, referred to the flexible woody vines, branches, and sticks which were interwoven to form walls, roofs, and fences. Since about 1810, it has been used as the

common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often con ...

for the Australian legume trees and shrubs such as Acacia species proper, '' Castanospermum australe'', and Sesbania species that can provide these branches.

History

The genus ''Acacia'' was considered to contain some leading to 1986. That year,

Leslie Pedley Leslie Pedley (19 May 1930 – 27 November 2018)IPNILeslie Pedley/ref> was an Australian botanist who specialised in the genus ''Acacia''. He is notable for bringing into use the generic name ''Racosperma'', creating a split in the genus, which r ...

questioned the

monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

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 Carl Friedrich Philipp (Karl Friedrich Philipp) von Martius (17 April 1794 – 13 December 1868) was a German botany, botanist and explorer. Between 1817 and 1820, he travelled 10,000 km through Brazil while collecting botanical specimens. His m ...

as the name of a section in ''Acacia'', but raised to generic rank in 1835. In 2003, Pedley published a paper with 834 new combinations in ''Racosperma'' for species, most of which were formerly placed in ''Acacia''. All but 10 of these species are native to

, where it constitutes the largest plant genus. In the early 2000s, it had become evident that the genus was not

and that several divergent lineages needed to be placed in separate genera. One lineage comprising over 900 species mainly native to

Wallacea Wallacea is a biogeography, biogeographical designation for a group of mainly list of islands of Indonesia, Indonesian islands separated by deep-water straits from the Asian and Australia (continent), Australian continental shelf, continental ...

, Australia,

, and

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. Comprising over List of islands of Indonesia, 17,000 islands, including Sumatra, ...

was not closely related to the much smaller African lineage group containing the

. This meant that the

n 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 ''Acacia penninervis'', commonly known as mountain hickory wattle, or blackwood, is a perennial shrub or tree is an ''Acacia'' belonging to subgenus ''Phyllodineae'', that is native to eastern Australia. Description The shrub or tree typically ...

'', allowing the largest number of species to remain in ''Acacia'', resulting in the two pan-tropical lineages being renamed ''

Vachellia ''Vachellia'' is a genus of flowering plants in the legume family, Fabaceae, commonly known as thorn trees or acacias. It belongs to the subfamily Mimosoideae. Its species were considered members of genus '' Acacia'' until 2009. ''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''. Following a controversial decision to choose a new type for ''Acacia'' in 2005, the Australian component of Acacia sensu lato now retains the name ''Acacia''. At the 2011 International Botanical Congress held in

Melbourne Melbourne ( , ; Boonwurrung language, Boonwurrung/ or ) is the List of Australian capital cities, capital and List of cities in Australia by population, most populous city of the States and territories of Australia, Australian state of Victori ...

, Australia, the decision to use the name ''Acacia'', rather than the proposed ''Racosperma'' for this genus, was upheld. Other Acacia s.l. taxa continue to be called ''Acacia'' by those considering the entire group as one genus. The Australian species of the genus '' Paraserianthes'' ''s.l.'' ,namely '' P. Iophantha'', are deemed its closest relatives. The nearest relatives of ''Acacia'' and ''Paraserianthes s.l.'' in turn include the Australian and

Southeast Asia Southeast Asia is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of the Mainland Au ...

n genera '' Archidendron'', ''

Archidendropsis ''Archidendropsis'' is a genus of flowering plants in the family Fabaceae. It includes 11 species, which are native to Australia, New Guinea, the Bismarck Archipelago, Solomon Islands, and New Caledonia.Pararchidendron'' and '' Wallaceodendron'', all Mimosoideae.

Species

The names of more than 1,080 species of ''Acacia'', mostly native to Australia, have been accepted by

Plants of the World Online Plants of the World Online (POWO) is an online taxonomic database published by the Royal Botanic Gardens, Kew. History Following the Convention on Biological Diversity, the Royal Botanic Gardens in Kew launched Plants of the World Online i ...

as of January 2025.

Fossil record

An ''Acacia''-like long

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

seed pod has been described from the

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

of the Paris Basin. ''Acacia''-like fossil pods under the name ''Leguminocarpon'' are known from late

Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...

deposits at different sites in

Hungary Hungary is a landlocked country in Central Europe. Spanning much of the Pannonian Basin, Carpathian Basin, it is bordered by Slovakia to the north, Ukraine to the northeast, Romania to the east and southeast, Serbia to the south, Croatia and ...

. Seed pod

s of †''Acacia parschlugiana'' and †''Acacia cyclosperma'' are known from Tertiary deposits in

Switzerland Switzerland, officially the Swiss Confederation, is a landlocked country located in west-central Europe. It is bordered by Italy to the south, France to the west, Germany to the north, and Austria and Liechtenstein to the east. Switzerland ...

. †''Acacia colchica'' has been described from the

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

Georgia Georgia most commonly refers to: * Georgia (country), a country in the South Caucasus * Georgia (U.S. state), a state in the southeastern United States Georgia may also refer to: People and fictional characters * Georgia (name), a list of pe ...

west of the Likhi Range.

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58pollen Pollen is a powdery substance produced by most types of flowers of seed plants for the purpose of sexual reproduction. It consists of pollen grains (highly reduced Gametophyte#Heterospory, microgametophytes), which produce male gametes (sperm ...

of an ''Acacia'' species has been described from western Georgia, including

Abkhazia Abkhazia, officially the Republic of Abkhazia, is a List of states with limited recognition, partially recognised state in the South Caucasus, on the eastern coast of the Black Sea, at the intersection of Eastern Europe and West Asia. It cover ...

. Australia's oldest fossil ''Acacia'' pollen are recorded from the late

, 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 Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...

and one (''

Acacia heterophylla ''Acacia heterophylla'', the highland tamarind,Forestry Abstracts, University of Oxford Commonwealth Forestry Bureau, p.327, 1939 is a tree (or shrub in its higher places) Endemism, endemic to Réunion, Réunion island where it is commonly named ...

'') is native to

Mauritius Mauritius, officially the Republic of Mauritius, is an island country in the Indian Ocean, about off the southeastern coast of East Africa, east of Madagascar. It includes the main island (also called Mauritius), as well as Rodrigues, Ag ...

and

Réunion Réunion (; ; ; known as before 1848) is an island in the Indian Ocean that is an overseas departments and regions of France, overseas department and region of France. Part of the Mascarene Islands, it is located approximately east of the isl ...

in the Indian Ocean. 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 Mulga woodlands. In Australia, ''Acacia'' forest is the second most common forest type after

eucalypt Eucalypt is any woody plant with Capsule (fruit), capsule fruiting bodies belonging to one of seven closely related genera (of the tribe Eucalypteae) found across Australia: ''Eucalyptus'', ''Corymbia'', ''Angophora'', ''Stockwellia'', ''Allosyn ...

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. Many reptiles feed on the sap, such as the native house gecko in Australia. The sap is also consumed by bugs (Hemiptera), such as ''Hackerobrachys viridiventris''' and '' Sextius virescens''.

''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. * Acacia adunca *

Acacia baileyana ''Acacia baileyana'', commonly known as Cootamundra wattle, Bailey's wattle or golden mimosa, is a species of flowering plant in the family Fabaceae and is endemic to a restricted area of New South Wales, although it has become Naturalisation (b ...

* Acacia cyclops * Acacia dealbata * Acacia decurrens * Acacia elata * Acacia fimbriata * Acacia implexa * Acacia longifolia *

Acacia mearnsii ''Acacia mearnsii'', commonly known as black wattle, late black wattle or green wattle, is a species of flowering plant in the family Fabaceae and is Endemism, endemic to south-eastern Australia. It is usually an erect tree with smooth bark, Glo ...

* Acacia melanoxylon * Acacia paradoxa * Acacia podalyriifolia * Acacia pycnantha * Acacia saligna * Acacia stricta

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 Aboriginal Australians are the various indigenous peoples of the Mainland Australia, Australian mainland and many of its islands, excluding the ethnically distinct people of the Torres Strait Islands. Humans first migrated to Australia (co ...

have traditionally harvested the seeds of some species, to be ground into flour and eaten as a paste or baked into a cake. Wattleseeds contain as much as 25% more protein than common cereals, and they store well for long periods due to the hard seed coats. In addition to consuming the edible seed and gum, Aboriginal people also employed the timber for implements, weapons, fuel and musical instruments. A number of species, most notably '' Acacia mangium'' (hickory wattle), ''A. mearnsii'' (black wattle) and ''A. saligna'' (coojong), are economically important and are widely planted globally for wood products,

tannin Tannins (or tannoids) are a class of astringent, polyphenolic biomolecules that bind to and Precipitation (chemistry), precipitate proteins and various other organic compounds including amino acids and alkaloids. The term ''tannin'' is widel ...

, firewood and fodder. ''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

adhesive Adhesive, also known as glue, cement, mucilage, or paste, is any non-metallic substance applied to one or both surfaces of two separate items that binds them together and resists their separation. The use of adhesives offers certain advantage ...

s. In

Vietnam Vietnam, officially the Socialist Republic of Vietnam (SRV), is a country at the eastern edge of mainland Southeast Asia, with an area of about and a population of over 100 million, making it the world's List of countries and depende ...

, 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 ''

'', '' A. dealbata'' and '' A. pravissima'' – are cultivated as ornamental garden plants. The 1889 publication ''Useful Native Plants of Australia'' describes various uses for eating.

References

External links

* — multi-access key for identifying Australian Acacias {{Authority control Fabaceae genera Mimosoids