Acacia harpophylla

Description

Acacia harpophylla is a root-suckering tree with hard, furrowed, almost black bark. Its branchlets are either softly hairy or glabrous. The sickle-shaped phyllodes are leathery, silky-haired, 100–200 mm long and 7–20 mm wide, with three to seven prominent parallel veins. Golden yellow flowers appear in spherical heads 5–8 mm across, each containing 15 to 35 flowers, on hairy peduncles 10–20 mm long.

Flowering occurs from July to October. The pods are subterete, straight to slightly curved, up to 200 mm long and 5–10 mm wide, crusty and glabrous, slightly raised over and constricted between the seeds. Seeds are oblong or broadly elliptic, flat but thick, 10–18 mm long, with a thread-like attachment but no aril.

Distribution and habitat

These woodlands extend from 20° S into northern New South Wales. Brigalow occurs from coastal areas receiving over 900 mm rainfall per year to semiarid 500 mm regions, though it is primarily a semiarid zone species. Gidgee replaces brigalow as rainfall drops westward, from 650 to 300 mm, and reaches about 12 m in height.

In north-western areas black gidgee (Acacia argyrodendron) replaces brigalow, while in Central-Western districts boree (Acacia tephrina) forms woodlands on cracking clay soils, often with Acacia cambagei. Georgina gidgee (Acacia georginae) woodlands occur in the 200–250 mm rainfall belt. In New South Wales brigalow is found from Roto south to Hungerford west and Willow Tree east along the Great Dividing Range; in Queensland it extends north to Townsville.

Response to fire

Brigalow communities generally resprout well after fire, with brigalow itself sprouting freely from the butt, roots and living stems. Gidgee and blackwood have limited capacity to resprout following fire. An exception occurs in softwood scrubs, dense brigalow communities with fire-sensitive species. Fire would be rare naturally in these woodlands because pasture is sparse, consisting of Chloris, Setaria, Dicanthium, Sporobolus and Eragrostis species.

Large-scale land clearing

In 1962, the Brigalow Land Development Scheme, also called the Fitzroy Basin Land Development Scheme, began rapidly clearing huge areas of brigalow ecosystems in Queensland for farming and grazing. This cleared 4.5 million hectares, or 21% of Australia’s brigalow, and caused heavy runoff into waterways. Today, less than 1000 square kilometers remain—just 10% of the original cover—and clearing continues, though at a slower pace. These brigalow vegetation groups can be listed as endangered under Australia’s Environment Protection and Biodiversity Conservation Act 1999, with ongoing land clearing for crops and pasture as the main threat.

Did You Know?

• The specific epithet harpophylla refers to the curved phyllodes.
• Acacia harpophylla was first formally described in 1864 by George Bentham in Flora Australiensis.
• The description was based on an unpublished description by Ferdinand von Mueller of specimens collected by Anthelme Thozet near Rockhampton.