Synonyms – Senegalia, Racosperma
Family: Fabaceae (was Mimosaceae)Names:
Acacia was the name of a thorny Egyptian tree.
Wattle comes from British settlers making wattle and daub buildings using Callicoma serratifolia branches which was then called Black Wattle and is similar to the other Acacias of the area.
Summary:Trees or shrubs often with flattened petioles for "leaves" or bipinnate leaves with many small leaflets. The flowers are usually yellow and composed of many tiny flowers in spherical of cylindrical clusters in the axils of leaves or sprays at the ends of branches. Some species are spiny. There are over 500 native species in WA. In 1986 the Acacia genus was split into the Acacia, Senegalia and Racosperma genera.
Description:See the Weedy_Acacia_Key
First leaves:Alternate. Usually with many leaflets.
Leaves:Alternate leaves with leaflets that have leaflets (bipinnate) or are reduced to a flattened petiole (phyllode). The seedling and juvenile leaves are usually bipinnate and the mature plants may be phyllodes or bipinnate depending on the species. Some species may be leafless. Some may be spiny.
Stipules - Papery or spiny.
Petiole - May be flattened into a leaf like structure. Base swollen and often wrinkled.
Blade - Bipinnate with many leaflets or a leaf like phyllode.
Stems:Single or multi stemmed. Mainly trees or shrubs.
Flower head:Cylindrical or globular in the axils or in sprays at the ends of branches. Often yellow.
Flowers:Bisexual, small, often with a small bract at the base. Radially arranged floral segments of similar size (actinomorphic).
Ovary - Usually stalkless, many ovules.
Style - Threadlike.
Sepals - 4 or 5, usually free
Petals - 4 or 5, usually free
Stamens - Many, free, stick out from the flower.
Anthers - All fertile, 2 celled, opening by a lengthwise slit.
Fruit:Pod that usually drops seed when ripe by opening 2 valves.
Seeds:Usually somewhat flattened. Funicle often threadlike and thickened to form a white, yellow or red fleshy aril.
Roots:Taproot with many laterals.
Key Characters:Leaves pinnate or a phyllode.
Flowers bisexual, actinomorphic, small, numerous, in a globular head or cylindrical spike.
Sepals more than 2 or absent.
Stamen all free, more than 10, usually < 0.5 mm long, white, cream, yellow or orange yellow.
Seeds in a pod.
From Dr. Judy Wheeler and Nancy Burbidge.
Perennial. Many species are trees.
Physiology:Gums of some species used commercially.
Reproduction:By seed. Some species sucker or layer.
Flowering times:Mainly spring.
Seed Biology and Germination:Seed is often dormant, often has a long life in the soil and may require fire for full germination.
Vegetative Propagules:Some species sucker or layer.
Hybrids:Hybridisation between species does occur.
Allelopathy:Population Dynamics and Dispersal:
Spread by seed. Often spread by birds.
Origin and History:Australia, Africa, Asia, America.
In 1986 the Acacia genus was split into the Acacia, Senegalia and Racosperma genera.
Distribution:ACT, NSW, NT, QLD, SA, TAS, VIC, WA.
More than 500 species in WA. About 900 species native to Australia
Temperate, tropical, sub tropical and arid regions.
Many commercial species used for ornamentals, revegetation, gums, posts and craft.
Detrimental:Several weedy species.
In WA, Acacia longifolia, Acacia dealbata, Acacia pycnantha, Acacia melanoxylon and Acacia baileyana can be particularly invasive.
Toxicity:Generally, Acacias cause few problems to stock grazing amongst them.
Coast Myall and Deane's Wattle have been recorded as toxic and contain cyanogens. Lopping and wilted leaves of Coast Myall are particularly dangerous.
Young plants of Acacia dilatata have been implicated in sheep deaths at Watheroo. A number of species in eastern Australia have been suspected to be toxic. The wood of a number of species may cause festering of scratches. Some species contain saponin.
Treatment:Remove stock if poisoning suspected.
Legislation:The Wildlife Conservation Act prohibits removal of native plants from the wild in their native range on government land.
Management and Control:Picloram, Garlon® and glyphosate are used for chemical control as overall sprays, stem injection, cut stump or topical application to trunk.
Use Garlon® 480 at 1:400 or Roundup® CT at 1:200 as an overall spray for control of juvenile trees and 2 L/ha Garlon® 480 for control of seedlings.
2 L/ha of Roundup® (360 g/L) controls seedlings in autumn winter and spring but 4 L/ha was required for late summer applications. Some species of Acacia are far more tolerant of glyphosate than others.
Fire destroys the mature trees but led to a mass germination of seedlings. However if these seedlings are controlled it very quickly reduces the seed bank in the soil. Seedlings tend not establish in mature stands.
A long term control plan is usually required for success.
Target areas that have been recently burnt because these will be more prone to invasion and the seed bank will be reduced due to the fire induced germination of seed.
1) In large dense stands, a hot fire may be used to kill old trees and encourage seed to germinate so that it may controlled by herbicides and reduce the soil seed bank.
2) Apply herbicides in spring.
3) For mature or juvenile trees, apply a mixture of 1 L of Access® in 60 L of diesel to the lower 500 mm of the trunk or inject the stems with 1 mL Tordon® Timber Control herbicide per 1.5 metres of height.
4) For seedlings, apply 4 L/ha of glyphosate (450 g/L) or spray until just wet with a mixture of 100 mL of glyphosate (450 g/L) per 10 L of water.
5) For juvenile trees, spray a mixture of 100 mL of glyphosate (450 g/L) plus 25 mL Pulse® Penetrant per 10 L of water onto the foliage until just wet.
6) Avoid further burning or denuding the area as this will encourage seedling establishment.
7) Repeat treatment every second year to ensure that no trees reach an age where they can set seed.
Some Acacia species may be more tolerant of glyphosate than others. If glyphosate is not providing adequate levels of control then use Garlon® 600 at the same rates as glyphosate above. Some Pilbara Acacias are tolerating 8 L/ha glyphosate450.
Most mature Acacias don't sucker or coppice when cut down or ring barked but juvenile plants or seedlings that have broken off often do re shoot. A large number of seedlings often emerge in the season after felling or burning and if these are not controlled then the infestation may become worse.
Herbicide resistance:None reported.
Biological Control:This is used on some species in South Africa.
Biocontrol is unlikely on most species because many have closely related, local native species. However, some invasive species like A.longifolia are on a different phylogenic branch to most species.
Related plants:See the Weedy_Acacia_Key
There are more than 500 native Acacia species in WA.
Weedy and look-alike species include
Acacia Hedge (Acacia paradoxa). Noxious weed.
Black Wattle (Acacia decurrens) Bark used for tanning.
Blackwood (Acacia melanoxylon) Bark used in tanning.
Blakely's Wattle (Acacia blakelyi) Used in revegetation.
Brigalow (Acacia harpophylla)
Burrow’s Wattle (Acacia burrowii)
Caterpillar Wattle (Acacia lasiocalyx) Used in revegetation.
Cedar Wattle (Acacia elata) Ornamental
Chisholm's Wattle (Acacia chisholmii)
Coast Myall (Acacia binervia) is toxic to stock.
Cootamundra Wattle (Acacia baileyana) Ornamental
Curracabah (Acacia concurrens)
Currawong (Acacia sparsiflora)
Cutch Tree (Acacia cutechu) Noxious weed.
Deane's Wattle (Acacia deanei)
Dwarf Silver Wattle (Acacia nano-dealbata)
Flinders Ranges Wattle (Acacia iteaphylla)
Gidgee (Acacia cambagei)
Georgina Gidgee (Acacia georginae) is toxic to stock.
Golden Wattle (Acacia pycnantha) Bark used in tanning.
Golden-wreath Wattle (Acacia saligna) Used in revegetation.
Gosford Wattle (Acacia prominens) Ornamental
Green Wattle (Acacia mearnsii) Bark used in tanning.
Hop Mulga (Acacia craspedocarpa)
Manna Wattle (Acacia microbotrya) Used in revegetation.
Mimosa bush (Acacia farnesiana was Vachellia farnesiana)
Motherumbah (Acacia cheelii)
Mountain Cedar Wattle (Acacia elata)
Mulga (Acacia aneura) Used for fodder.
Prickly Acacia (Acacia nilotica). Noxious weed.
Prickly Moses (Acacia pulchella)
Queensland Silver Wattle (Acacia podalyriifolia)
Red Wattle (Acacia sylvestris)
Silver Wattle (Acacia dealbata)
Snowy River Wattle (Acacia boormanii) Ornamental
Sweet Wattle (Acacia suaveolens)
Sydney Golden Wattle (Acacia longifolia)
White Sally (Acacia floribunda)
Acacia glaucescens is toxic to stock.
Plants of similar appearance:References:
Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P171.
Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia).
Bodkin, F. (1986). Encyclopaedia Botanica. (Angus and Robertson, Australia).
Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). P196-209. Diagrams.
Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P352-374. Photographs.
Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney).
Gardner, G.A. and Bennetts, H.W. (1956). The toxic plants of Western Australia. (West Australian Newspapers Ltd, Perth). P36.
Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (1997). Western Weeds. A guide to the weeds of Western Australia. (Plant Protection Society of Western Australia, Perth, Western Australia). P178-182.
Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).
Lazarides, M. and Cowley, K. and Hohnen, P. (1997). CSIRO handbook of Australian Weeds. (CSIRO, Melbourne). #3.x
Marchant et al (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P212. Diagrams.
McBarron, E.J. (1983). Poisonous plants. (Inkata Press, Melbourne). P132,134.
Meadly, G.R.W. (1965). Weeds of Western Australia. (Department of Agriculture - Western Australia).
Wilding, J.L., Barnett, A.G. and Amor, R.L. (1987). Crop weeds. (Inkata Press, Melbourne).
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