Three Australian invaders threatening SA environment

These alien invader plant species, all of which are acacias, grow rapidly in South Africa. By law, they must be removed and destroyed

The hickory or screw-pod wattle (Acacia implexa) is an erect tree up to 15m tall. It has a single stem or is divided near ground level into two or three main stems. The leaves are dark green, narrowly elliptic and sickle-shaped, 7cm to 20cm long and 6mm to 25mm wide, and narrow at the base. The bark is rough and greyish.

The flowers are arranged in globular heads, are creamy to pale yellow, and flower from December to March.

The pods are narrow (4mm to 7mm wide), coiled, and twisted to a length of 25cm. The seeds are dark brown. Hickory wattle is native to Australia. According to the South African National Biodiversity Institute (SANBI), A. implexa has been recorded in the Western Cape at Tokai forest, Stellenbosch and Wolseley.

Environmental and economic impact

This fast-growing tree invades agricultural lands, planted forests and disturbed areas. It can become highly invasive if not controlled. It spreads through suckers (shoots that grow from the base or the roots of the tree).

The National Environmental Management Biodiversity Act of 2004 (NEMBA) classes the tree as a Category 1a invasive plant, an invasive species requiring compulsory control.

“Any specimens of Category 1a listed species need, by law, to be eradicated from the environment. No permits will be issued,” states SANBI.