Silky acacia

General description

Medium-sized deciduous tree about 14 m tall with flat crown. Bark is fairly smooth, light brown and vertically striped when older. Leaves are 20 x 10 cm and bi-pinnately compound, with < 12 pairs of pinnae each bearing 30 pairs of oblong leaflets. Flowers have a cluster of silky-looking white/pink/red stamens and are borne in inflorescences in spring. Seedpods are flat, papery and ripen in February – March.

What you need to know

Although silky acacia is not a legally declared pest plant, it may still be invasive in some situations. Consider lower risk alternatives for your garden, such as native plants.

Habitats

Disturbed sites, riparian and forest margins, scrub, urban areas, gardens, roadsides.

Dispersal

Seeds dispersed by water and gravity. Human-mediated dispersal through deliberate plantings and movement of contaminated soil.

Impact on environment

Can form dense stands, out-competing native vegetation. Nitrogen fixer.

Control

Site Management

Follow up treated areas 3 times per year. Encourage natural regeneration of native plants or replant treated areas where possible after 2-3 treatments to establish dense ground cover and minimise reinvasion.

Recommended approaches

Physical control

Method: Dig out.

Plant parts requiring disposal: Seeds.

Disposal options: Remove to greenwaste or landfill if practical.

Biocontrol

Biocontrol is currently not available for this species.

Community agrichemical control recommendations

No qualifications: Cut stump and paste freshly cut base of stems with metsulfuron gel.

Basic Growsafe certified: Cut stump and spray freshly cut base with 1g metsulfuron-methyl per 1 L of water.

Certified Handler/Experienced agrichemical user: Drill and inject trees with 10g metsulfuron-methyl per 1L of water if safe to do so. Drill 18mm holes (tangentially angled downwards) in a spiral up the trunk.

For 50mm stems drill one hole. For 100mm stems drill two holes. For larger stems drill holes 150mm apart. Foliar spray seedlings with 5g metsulfuron-methyl per 10L of water and 20ml penetrant.

Safety notes

Large trees must not be drilled that are closer than 1.5 times the height of the tree from paths, walkways and property.

Trees over 4 metres in height should be removed by a qualified arborist.