What does it look like?
Brush wattle is a short-lived exotic tree, usually 5-10m tall. It has densely hairy twigs and bronze, hairy young shoots. Leaves are 20-30cm long, frond-like, alternate, and twice divided along the midrib. It has many tiny green-yellow flowers from May to August.
Flower heads resemble a bottle brush, and are followed by flat, green to brown seed pods, which contain 9-11 hard-coated black seeds about 7mm long.
Brush wattle prefers disturbed open land, especially scrubland, riverbanks, gum land, and coastal sites. It can persist in low forest for many years but does not tolerate deep shade and dislikes growing among species of similar or even lesser height, which makes it a true pioneer species.
Why is it a problem?
Brush wattle is fast growing and maturing, producing many long-lived seeds. Seeds are likely to be viable for at least 20 years. As it is also a nitrogen-fixing species, brush wattle is very successful in a range of environments. It re-seeds following disturbance by fire, machinery or non-selective spraying and recovers faster than native species.
It forms tall stands that over-top low-growing vegetation. Fortunately, native forest species will still establish under wattle, however open, low-growing vegetation is more negatively impacted, such as coastal or marginal forest.
Control methods
Physical control
Physical control is possible by either pulling out seedlings and small trees. For larger trees, cut the trunk into manageable sections to be dug out. Remove all roots to achieve eradication and beware that stumps will regrow.
Herbicide control
Cut larger trees and stump treat with metsulfuron-methyl 600g/kg (5g/L) or triclopyr 600 EC (50ml/L). Or
Spray in spring-summer with glyphosate (10ml/L) or triclopyr 600 EC (3ml/L).
CAUTION: When using any herbicide or pesticide, PLEASE READ THE LABEL THOROUGHLY to ensure that all instructions and safety requirements are followed.
Related links
http://www.nzpcn.org.nz/flora_details.aspx?ID=3287
http://www.nzflora.info/factsheet/Taxon/Paraserianthes-lophantha.html
https://www.weedbusters.org.nz/what-are-weeds/weed-list/brush-wattle
