Family: Fabaceae (Mimosoidae) – wattles, mimosa

Status:

Description:
Straggly evergreen shrub or small tree to 8m high, but usually smaller. The twigs are slightly ribbed, with the narrow raised ribs running down the stem from the base of each leaf. Leaves are compound, of numerous small leaflets similar to those of some wattles (Acacia species), but bigger than those of most south coast wattles. The cream flowers are also wattle-like, but are carried in bottlebrush style clusters. The pods are broad and flat, 8-12 cm long, containing 6-12 black shiny seeds, and are very similar to those of wattles.

Preferred habitat and impacts:
Cape wattle is a West Australian native which has been widely promoted as a garden plant in the last twenty years or so. It is now extensively naturalised in eastern Australia, where it invades bush around towns and gardens. It can become dominant in bush and coastal woodland.
It is a very fast growing plant tolerant of poor soils, and adapted to recolonising from seed after fires.

Dispersal:
Spread from seed in dumped garden waste, and by birds, ants and in contaminated soil and water. Like the true wattles, cape wattle produces huge seed crops, which are very long-lived in the soil. They are likely to germinate profusely after fire, so that they can go from being a minor weed to becoming dominant in burnt bush, if there is no control effort after a fire.

Look-alikes:
Distinguished from local native wattles by the bottlebrush-like flower clusters. The most similar south coast wattle is sunshine wattle (Acacia terminalis), which also has the ribbed stems, bipinnate (twice-compound) leaves, and flat brown seed pods. The leaves of sunshine wattle consist of 2-6 pairs of pinnae (leaflets), which are further divided into 8-20 pairs of pinnules (the ultimate small leaflets in a wattle leaf). There is a single conspicuous boat-shaped gland on the leaf stalk at the point where the first pair of pinnae meet the stalk. The leaves of cape wattle have many more leaflets (8-13 pairs of pinnae, each with 15-40 pairs of pinnules) and two raised red glands on the leaf stalk, one about half way between the junction of the leaf stalk with the branch and the first pair of pinnae, and one between the final pair of pinnae at the leaf tip.
The introduced garden plant, silk tree (Albizia julibrissen) has similar leaves and pods, but its flowers are pink. It has not been recorded escaping from gardens.

Control:
Fire can be used to stimulate bulk germination of the soil seed bank, as long as the resources are available to do follow-up control on the resulting seedlings. Spray or hand-pull these. Cut and paint or stem inject young vigorous plants. Old plants usually will not re-sprout if just cut down, without the use of herbicides.