Sydney Golden Wattle

Acacia longifolia (Andrews) Willd.

Synonyms - Racosperma longifolia. Mimosa longifolia.

Family: Fabaceae (was Mimosaceae)

Names:

Acacia was the name of a thorny Egyptian tree.
Longifolia refers to the long “leaves” (phyllodes).
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.
Sydney Golden Wattle refers to its abundance around Sydney, its flower colour and it is in the wattle or Acacia genus.

Other Names:

Golden Wattle
Sallow Wattle
White Sallow

Summary:

Sydney Golden Wattle (Acacia longifolia subsp. longifolia) is an invasive shrub or small tree to 1.5-10 m high x 1-25 m wide with dark grey, finely fissured bark and green foliage. The leaves are replaced by undivided leaf-like phyllodes that are 50-250 mm long and (4)10-35 mm wide and each face has 2-4 prominent longitudinal veins. The yellow flower heads are cylindric in shape, 20-50 mm in length and occur in pairs or singly in the phyllode axils. The seed pods are 50-150 mm long and 3-10 mm wide, thick and usually straight to slightly curved.
Native to New South Wales and Victoria, it is now a troublesome weed of roadsides and creeks, invading bushland around Albany. It flowers from June to October.
The closely related Coastal Wattle (Acacia longifolia subsp. sophorae) which is also native to eastern Australia, is weedy from Albany to east of Manypeaks. Coastal Wattle has fleshier phyllodes 50-120 mm long and 10-30 mm wide, cream flower heads and curved to somewhat contorted seed pods.

Description:

See the Weedy_Acacia_Key

Cotyledons:

Two.

First leaves:

Young leaves: Present on seedlings for the first year or two. They then develop into phyllodes, which are flattened leaf like petioles (leaf stalks). Hairless.

Leaves:

Alternate.
Stipules: Tiny, triangular, <1 mm long or obscure.
Phyllodes: 50-200(250) mm long x 4-35 mm wide, flat, narrowly egg shaped to elliptic, leathery. Hairless. Relatively straight with 2-3(5) obvious, lengthwise veins with obvious side veins and fainter network veins in between. Tip is rounded to pointed and sometimes with a sharp extension of the mid vein (mucro). Edges curved to somewhat parallel. 2-10 mm from the base of the phyllode is one small gland. The pulvinus is about 5 mm long. The pulvinus moves the leaf by changes in pressure.
Petiole - is the phyllode which is flattened and looks like a leaf.
Blade - None on mature trees. The leaf is replaced by a leaf-like phyllode.

Stems:

Initially angular, green to red green and becoming grey and rounder with age. 1-10 m tall and may be prostrate. Branchlets angled or flattened. Hairless to minutely hairy especially when young.
Bark: finely fissured.

Flower head:

Golden yellow, cylindrical rachis or dense spikes, 20-50 mm long and usually in pairs in the leaf axils. Main axis (rachis) is hairless and usually without flower stalks (peduncles). Bracteoles 0.3-0.5 mm long, with ciliate margins and fall off at flowering.

Flowers:

Many individual flowers on 2-5 mm stalks.
Ovary - Hairless to hairy.
Calyx - 4 short lobes with fine hairs or hairless.
Petals - 4. Free. Hairless.
Stamens -
Anthers -
Pollen: Trigo and Garcia (1990) have described pollen morphology.

Fruit:

Brown, straight or curled and twisted, rough, striate or wrinkled, narrow, cylindrical, leathery, beaked pod. 30-150 mm long, 3-10 mm wide. Slightly contracted between the lengthwise seeds. 4-10 seeds per pod.

Seeds:

Brown-black, shiny. Egg shaped to oblong or elliptic and sometimes irregularly shaped, 4 mm long. Seed stalk expanded near the seed. Seed stalk is white, thick and soft with 2 or more folds before it merges into the broad skirt-like junction (aril) with the seed.

Roots:

Taproot.

Key Characters:

It is distinguished by its phyllodes with 2-4 prominent primary veins and anastomosing secondary veins, smooth margins, conspicuous basal gland and commonly lemon-yellow spicate inflorescence.
Pairs of cylindrical rather than globular flower heads.

There are 2 sub species.
Acacia longifolia ssp. longifolia has straight sided phyllodes (leaves) up to 200 mm long x 15 mm wide that are usually thin and pliable and has fairly straight pods.
Acacia longifolia ssp. sophorae has thicker, shorter, broader and more rounded leaves up to 120 mm long x 30 mm wide and the pods are usually coiled.

Biology

Life cycle:

Perennial, tree or spreading shrub up to 8 m high. The main flowering period is June to October. Seedlings germinate in winter producing acacia type juvenile leaves (many leaflets arranged like a feather) for the first season or two. The juveniles quickly grow to maturity and become prolific producers of pods and seeds in 2-3 years. Thickets are often formed and few species grow in the understorey. Fire or denudation may kill older trees and this leads to a massive germination of fast growing seedlings that out compete most other plants. It lives for around 50 years in it native range but commonly dies within 25 years in other areas. Acacia longifolia ssp. sophorae has a shorter lifespan.
In South Africa, there is a reduction in growth during the spring when flowering occurs. In years of high pod production there is reduced phyllode growth and vice versa (Dennill,1987)

Physiology:

Drought tolerant once established.
Fixes atmospheric nitrogen.
Grows best in full sun to partial shade.

Reproduction:

By seed.

Flowering times:

July to September in WA.
June to October in SA.
Late winter to spring in SE Australia.

Seed Biology and Germination:

Soil seed banks often exceed 100 seed/m2.
Seed may remain dormant for more than 10 years. Around 10% of fresh seed germinates each year without dormancy.
Many seeds germinate after fire.

Vegetative Propagules:

None.

Hybrids, varieties, cultivars and subspecies:

Forms hybrids with Acacia oxycedrus, Acacia floribunda and Acacia mucronata.
Hybrids between the 2 sub species longifolia and sophorae are common where they intermix.
Sub species sophorae tends to be lower growing, usually < 5 m tall, spreading horizontally with the ends of branches bending upward and has fleshier 'leaves', cream to white flower heads, curved to somewhat contorted pods and is mainly on the coastal dunes. The length to width ratio of the leaves is less than 5 whereas in sub species longifolia it is greater than 7.
Flora of Australia distinguish them as follows:
subsp. longifolia has phyllodes 5-20 cm long and 5-15 mm wide, mostly broadest near or below middle, mostly thin and pliable, commonly narrowing gradually towards apex; pods mostly straight (near-coastal tracts and hinterland)
subsp. sophorae has phyllodes 5-12 cm long and 10-30 mm wide, often thick and sometimes fleshy, mostly broadest near or above middle, commonly narrowing ±abruptly towards apex; pods mostly coiled or contorted (mostly coastal)

Ecology, Population Dynamics and Dispersal:

Spread by seeds. Birds, ants, water flows and transport of garden refuse or soil are the greatest vectors for spread. Bronze-winged Pigeons appear to be important in spread in WA.
Young plants reshoot vigorously after fire. There is often a mass germination of seedlings following fire or other denudation events. This usually leads to an increases in density following denudation events. It is a very rapid grower and competitive (Lord, 1964).
Older plants tend to die after hot fires.

Origin and History:

Australia. Native to the eastern states and introduced to WA where it is spreading rapidly.

Distribution:

ACT, NSW, SA, TAS, VIC, WA.
Argentina, New Zealand, Portugal, South Africa, Spain, USA, Uruguay.

Courtesy Australia's Virtual Herbarium.

Habitats:

Climate:

Temperate. Usually most invasive in areas with greater than 500 mm rainfall.

Soil:

Prefers free draining soils of granitic, basaltic or sandstone origin. Also river flats. Sands, sandy loams, acid soils and sand dunes.
Tolerates a wide range of soils.

Plant Associations:

River red gum, heathland, woodland, forest.

Significance:

Beneficial:

Used for gum, timber, fuel wood, pollen, fibre, aboriginal food and as an ornamental tree.
Timber is light, tough and hard and is used for tool handles. The heartwood is brown, streaked with black and pale yellow towards the outside.
Used as a nurse tree on infertile sites for eucalypt plantations (Smith et al, 1989)
Used for dune stabilisation in South Africa but is not favoured because of its invasive potential (Avis, 1989)

Detrimental:

Invasive weed in WA, SA, Victoria and South Africa.
Pieterse and Cairns (1988) believe that the increased invasive potential in new habitats is due to increased seed production, which was regulated by natural enemies in the home range.
As it increases soil nitrogen levels the persistence of some natives is decreased.
It forms thick stands crowding out understorey species and reducing overstorey regeneration and recruitment.

Toxicity:

Possibly toxic to goats. Contains HCN. Generally it is not grazed by stock.

Symptoms:

May include excitement, struggling, shivering, fast heart and respiration rate, dizziness and gasping.

Treatment

As for HCN.

Legislation:

None

Management and Control:

Picloram, Garlon® and glyphosate are used for chemical control as overall sprays, stem injection, cut stump or topical application to the trunk.
Pieterse (1994) has used Garlon® 480 at 1:400 and Roundup® CT at 1:200 as an overall spray for control of juvenile trees and 2 L/ha Garlon® 480 for control of seedlings.
Pieterse and McDermott (1994) found that 2 L/ha of Roundup® (360 g/L) controlled seedlings in autumn winter and spring but 4 L/ha was required for late summer applications.
Fire destroys the mature trees but led to a mass germination of seedlings. However if these seedlings are controlled it reduced the seed bank in the soil by 90%. Seedlings do not establish in mature stands (Pieterse and Cairns, 1988)
Macdonald et al (1989) described the need for a long term control plan. They cite the South African experience where 35 years of piecemeal control was ineffective but consistent removal of all trees greater than 1.8 m tall is leading to a reduction in the infestation over the last ten years.
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.
Seedlings can be hand pulled. Young plants tend to break off and regrow from the base and need to be dug out or the base sprayed with a mixture of 1 L Access® in 60 L of diesel.

Thresholds:

Eradication strategies:

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.
Larger trees with trunks greater than 100 mm diameter can be cut with a chain saw close to the ground and these usually don't re shoot. However there are some varieties that regularly reshoot after cutting. Smaller trees tend to reshoot unless they are severed below ground level or the cut stump is painted immediately with glyphosate or triclopyr.

Herbicide resistance:

None reported.

Biological Control:

Biocontrol is being used successfully in South Africa (Moll and Trinder-Smith, 1992).

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.
Racosperma species.

Plants of similar appearance:

Acacia obtusifolia has resinous margins on the more leathery phyllodes and usually flowers much later in November to January and spreads mainly by suckering.
Acacia alpina
Acacia courtii
Acacia dallachyana
Acacia longissima
Acacia maidenii

References:

Avis, (1989).

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P424.

Blood, K. (2001). Environmental weeds: a field guide for SE Australia. (CH Jerram & Associates, Australia). P84. Photo.

Cunningham, G.M., Mulham, W.E., Milthorpe, P.L. and Leigh, J.H. (1992). Plants of Western New South Wales. (Inkata Press, Melbourne). P349. Photo.

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney). P399.

Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #4.67.

Lord, E.E. (1964). Shrubs and trees for Australian gardens. (Fourth edition. Lothian, Melbourne.)

Macdonald et al (1989).

Maslin, B.R. (2001) Wattle. Acacias of Australia. CD.

Moll and Trinder-Smith, (1992).

Moore, J.H. and Wheeler, J.R. (2008). Southern Weeds and their Control. (Second Edition). Department of Agriculture and Food Western Australia. P168. Photos.

Muyt, A. (2001). Bush Invaders of South-East Australia: a guide to the identification and control of environmental weeds found in South East Australia. (R.G and F.J. Richardson, Australia). P15-158. Photos.

Pieterse (1994).

Pieterse and Cairns (1988).

Pieterse-PJ; McDermott (1994).

Tame, T.(1992). Acacias of Southeast Australia. Kangaroo Press, Kenthurst, NSW, Australia. P32. Diagram.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.