Silver wattle
Botanical Name
Acacia dealbata
Family
Fabaceae (pea)
Also known as
Racosperma dealbatum
Where is it originally from?
Australia
What does it look like?
Shrub to large tree with suckering roots and ribbed, densely hairy twigs. Frond-like leaves (20-30 cm) are arranged alternately on stems, twice divided along the midribs, with 10-21 pairs of main subdivisions, and 25-40 pairs of bluish, narrow leaflets (2-4 x 1 mm). Clusters of numerous fluffy yellow flowers (Jul-Sep) are followed by straight, hairless seed pods (50-100 x 8-12 mm).
Are there any similar species?
Many Acacia species, and Paraserianthes lophantha, are similar.
Why is it weedy?
Produces many long-lived seed and suckers when roots are damaged. Grows rapidly, and tolerates hot to cold temperatures, poor soils (fixes own nitrogen), damp to dry conditions, and damage. Possibly allelopathic (able to produce toxins that poison the soil to discourage growth of other plants).
How does it spread?
Limited spread of seed and suckers through soil and water movement. Plantations, waste places and riverbeds are sources of infestations.
What damage does it do?
Forms large, dense, long-lived stands in disturbed habitats. Native forest species establish under wattle so long-term impacts are usually confined to open and low-growing vegetation types. Rotting matter affects water quality. Large stands increase water runoff in winter, less in summer, causing seasonal drought and flooding.
Which habitats is it likely to invade?
Disturbed forest and shrubland, short tussockland, bare land, river systems, and cliffs.
What can I do to get rid of it?
Only control where wattle is a recent threat, of low incidence or poses a high ecological threat.
1 Physical removal - Hand pull or dig seedlings (all year round). Ensure minimum soil disturbance.
2. Cut and paste - Cut the stem as close to the ground as possible. Apply a solution of diesel and triclopyr (20:1 diesel:triclopyr) or commercial formulations (120g triclopyr/l of oil or product containing triclopyr and picloram 50ml/L water mix) over the entire exposed surface of the freshly cut stump, i.e. top and sides.
3. Basal spray stems up to 20cm diametre with X-Tree Basal. Ensure the base is thoroughly covered at ground level.
4. Drill or Frill - Drill downward sloping holes around the circumference of the trunk about 8-10 cm apart, or Frill (make deep cuts into the sapwood at regular intervals around the base of the tree, taking care not to ring-bark the plant). Fill the holes or saturate the cuts with metsulfuron-methyl 600 g/kg (20-50g/L + penetrant) or a product containing 100g picloram+300g triclopyr/L (undiluted).
5. Foliar spray seedlings and small plants up to 1.5m high - Apply Triclopyr herbicide (600g/L active ingredient) at 6ml/L plus organosilicone penetrant (1ml/L) to thoroughly wet all parts of plant. Or apply Picloram/triclopyr herbicide (picloram 100g/l and triclopyr 300g/l active ingredient) at a rate of 6ml/L plus organosilicone penetrant (1ml/L) to thoroughly wet all parts of plant.
Note: Tricolopyr and picloram herbicides are ‘grass friendly’ but overspray will kill other (desirable) broadleaf plants. Picloram has residual activity in the soil which may leach through soil and kill other plants. Do not use under and around other (desirable) broadleaf plants. Do not use over or near water bodies or wetlands.
CAUTION: When using any herbicide or pesticide, PLEASE READ THE LABEL THOROUGHLY to ensure that all instructions and directions for the purchase, use and storage of the product, are followed and adhered to.
What can I do to stop it coming back?
Roots sucker and reseeds profusely in bared areas, resprouts from cut trunks and high light levels encourage seed germination . Light lover, dislikes growing amongst species of similar height such as pioneer species. Succeeded in tall canopy habitats by taller native species where their seedlings exist so these sites can be left to regenerate (20-40 years). Amongst well established, tall native vegetation, regeneration can be speeded by wattle control. Clear all roads, quarries and other sources. Maintain native groundcover at all times.
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