Is your Acacia friend or foe?

Acacia from the Eastern States are invading our bushland and a priority for removal, but take care not to confuse them with our endemic Acacia species.

There are over 1350 species of Acacia found across the world, and almost 1000 of these are found within Australia. Commonly known as Wattle, Acacia are the largest genus of vascular plants in Australia with the Golden Wattle (Acacia pycnantha) being Australia’s national floral emblem. Acacia occupy vast areas in the southern half the globe but are particularly prevalent in arid and semi-arid regions (although also occurring in sub-alpine and coastal areas).

Their wide distribution is attributed to range of plant traits, making them highly competitive when grown outside their natural range. Acacia generally have long-lived seeds, some surviving more than a decade in the soil seed bank. When grown in their own natural geographic locations, local insects predate on their seeds, in turn providing natural control methods. When Acacia species from the eastern states occur in Western Australia, this natural control does not occur and several of these eastern states’ species are invading our bushlands on the Swan Coastal Plain.  

Acacia iteaphylla (Flinders Range Wattle) and Acacia longifolia (Sydney Golden Wattle) are highly invasive weeds in Western Australia. Both Acacias have long lived seeds (seeds of A. longifolia can persist for up to two decades in the right conditions) and germinate readily. As nitrogen fixers, they also encourage exotic grasses to invade, increasing the risk of bushfire. These Acacia species, as well as A. floribunda (more recently observed in the Jarrah Forest) should be a priority for removal. Cutting at the base, ringbarking or bulldozing and hand pulling seedlings, followed by herbicide application, provides good control. Mass germination can be triggered by mechanical disturbance; therefore, the optimum treatment times occur immediately prior to seeding (generally between March-August).

When removing your invasive Acacia, take care not to confuse them for our important native wattles, particularly our coastal wattle (Acacia cyclops), tooth-bearing acacia (A. dentifera), prickly moses (A. pulchella) and narrow winged wattle (A. stenoptera). These local wattles are common to Banksia Woodlands and provide important habit for native fauna. Refer to florabase for plant identification and control methods: https://florabase.dpaw.wa.gov.au