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Acacia aneura (Family Fabaceae)

Mulga

Distribution:

It is widely distributed in dry areas of central and southern Australia, but it is rarely found in the Simpson and Great Victoria Deserts. The latitudinal range is 21-33o S and it is found from near sea level to about 1000 m. (NSW, QLD, SA, WA, NT)

Features:

A bushy, nitrogen-fixing shrub or small tree up to about 15 m tall. Its form and phyllode shapes are exceptionally variable. The bark is dark grey and fissured and the branchlets are angular. Phyllodes range from 2-25 cm long and 1-12 mm broad. They may be round or flat, straight or curved but are usually leathery. Flowers are in dense cylindrical spikes 1.5-2.0 cm long. Pods are flat and papery 2-5 cm long and 7-15 mm wide. Flowering time depends on favourable weather conditions. There are about 66 000 viable seeds per kilogram. Seeds need pre-treatment with very hot water for one minute to promote germination.

Ecology/Way of Life:

This acacia occurs mainly in the arid zone but extends into semi-arid areas. The annual rainfall is 200-400 mm but in many places mulga grows in hollows or at the base of slopes where it receives additional run-on water. It is often found on flood plains but only rarely on hill slopes and ridges. The denser stands are usually on infertile, well-drained, red earths or sandy soils. It is a dominant species of arid and semi-arid zone open woodlands and tall, open shrublands. This acacia may be partly defoliated by a range of insects and have its roots damaged by termites.

Interaction with Humans/Threats:

Mulga forms a major part of the dry-range diet of sheep in Australia but they need high quality feed to supplement it. The timber is heavy, hard and durable, it turns well and takes a high polish. It makes excellent firewood and is often used for fence posts. It is a useful species in arid areas for shade and shelter and its attractive silvery grey foliage makes it a popular choice for ornamental plantings. Some Aborigines ground its seeds to make flour and resin from the desert form of mulga was used as an adhesive. Its slow growth rate and limited ability to reshoot after fire, excessive browsing or cutting may limit its use.

Other Comments: Acacia aneura was named in 1855 by Ferdinand J.H. von Mueller, Government Botanist of Victoria; the name is based on Greek: akakia = thorny plant, specifically Acacia arabica; a = not, and neuron = nerve, referring to the lack of conspicuous veins on the phyllodes.

Further Reading:

Boomsma, C.D. and Lewis, N.B. 1980. The native forest and woodland vegetation of South Australia. South Australian Woods and Forests Department Bulletin 25. Adelaide.

Doran, J.C. and Turnbull, J.W. (eds.) 1997. Australian trees and shrubs; species for land rehabilitation and farm planting in the tropics. ACIAR Monograph no. 24. Australian Centre for International Agricultural Research, Canberra. 384p.

Maslin B.R. 1981. Acacia. In: Jessop, J. (ed.) Flora of central Australia, 115-142. Reed, Sydney.

Whibley, D.J.E. and Symon, D.E. 1992. Acacias of South Australia. Handbook of the flora and fauna of South Australia. Rev. 2nd ed. South Australian Government Printer, Adelaide.

Topics: Aboriginal resources Climatic zones Soils Vegetation types Timber Nitrogen-fixation

Acknowledgments:

Text & map from Australian Trees and Shrubs, courtesy Australian Centre for International Agricultural Research; text edited by J. Turnbull; photo courtesy M. McDonald.

Sponsored by:

Maurice McDonald/ACIAR


 

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