Prickly Acacia

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Acacia nilotica


This umbrella shaped, perennial tree can grow from 4 to 10 metres. Young shrubs form dense thorny thickets, while mature trees are usually single stemmed, with spreading branches and have lost most of their thorns.

Leaves are fern-like, with 4 to 10 pairs of leaf branches and 10 to 20 pairs of small, narrow, green leaves on each branch. Pairs of thorns grow at the base of the leaves.

Flowers are golden yellow, ball shaped and 1 centimetre wide. They grow on stems from leaf joints with 2 to 6 flowers per group. It flowers in summer and autumn.

Seed pods are 10 to 15 centimetres long, cylindrical with narrow constrictions between seeds; they are grey when ripe.

Habitat it grows in many soil types, particularly coastal clays, bore drains and watercourses.

Weed characteristics can outcompete pasture for water and causes soil degradation. It alters natural grasslands into thorny scrub and thickets. Thorny thickets interfere with mustering, movement of stock and access to water.

Dispersal of seed is via livestock and the seed takes up to six days to pass through the animal’s digestive system. Stock movement and transportation thus assists the further spread.

Declaration Details

This species is a Class 2 declared plant under Queensland legislation and is listed as a Weed of National Significance.

How to act

Mechanical control is most cost effective for initial removal of dense infestations. Windrowing and burning to remove the debris will allow for regeneration of natural vegetation. Cut stump or basal barking is effective for isolated established plants. Young plants can be physically removed. Foliar spraying is effective when plant is actively growing. Control should be carried out prior to seed set with follow up monitoring and control of emergent growth important. Fire may be essential to stimulate the dormant seed bank so seedlings can then be controlled with herbicide.

Refer to Weed Control Methods.


Related information

Prickly Acacia © NQ Dry Tropics 2011
Prickly Acacia © NQ Dry Tropics 2011
Prickly Acacia Eradication Project
Prickly Acacia Eradication Project

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