Acacia aulacocarpa

golden-flowered salwood


Acacia aulacocarpa

Benth 1842

pronounced: uh-KAY-shuh aw-lack-ow-KAR-puh

(Mimosaceae — the wattle family)

synonym — Racosperma aulacocarpum

(Benth.) Pedley 1984

pronounced: rak-ow-SPUR-muh aw-lack-ow-KAR-pum

common names: golden flowered salwood, hickory wattle, ironbark wattle

native 4Acacia is from the Greek ακις (akis), a thorn or spike; aulacocarpa is from αυλαξ, αυλακος (aulax, aulakos), a furrow made in ploughing, and καρπος (karpos) fruit. Salwood is from sallow-wood, sallow being a willow, especially one of the broader-leafed kinds with comparatively brittle twigs; the word sallow derives from salix, the Latin word for a willow.

This wattle occurs naturally in Australia, New Guinea and Indonesia, mainly in hot humid and sub-humid zones of the tropics and subtropics. It has a discontinuous distribution along coastal areas and adjoining tablelands of the Great Dividing Range in eastern Queensland from the Mt Windsor Tableland (c. 25 km east of Daintree) to just south of Brisbane and into northern NSW near Grafton. It is also found on a number of off-shore islands. Despite its extensive distribution, it is a relatively uncommon species, as populations tend to be locally confined to creek banks or run-on sites near rock outcrops. The tree photographed is by the roadside on the western section of Apjohn Street, Horseshoe Bay, close to the bank of Endeavour Creek.

There is a considerable variation in habit between some populations: for instance, plants occurring in coastal areas of North Keppel Island have a compact, domed habit only 50 cm tall, whereas those along rivers in the forests of Finch Hatton Gorge are medium-sized trees to 12 m tall, with trunks of a DBH of up to 40 cm. The one photographed is about 4 m high, with the trunk multi-branched from just above ground level. Some naturally occurring hybrids are found, such as with Acacia celsa (at Paluma Dam) and with Acacia crassicarpa (at Bluewater Creek, north of Townsville).

The bark is hard, often brownish, about 1 cm thick, longitudinally fissured, peeling in long strips. The phyllodes are straight or falcate, acute or sub-acute, 5 – 15 by 0.5 – 3.5 cm, 3 – 12 times long as wide, glabrous, greyish green or dull grey, with 3 prominent longitudinal veins sometimes crowded towards the lower margin at the base, usually not yellowish, and with many parallel secondary veins.

The inflorescence is a spike, 2 – 6 cm long. The flowers are yellow or bright yellow, strongly but not particularly pleasantly perfumed. Most flowers in each spike are male, with occasional bisexual flowers.

The pods are 1.5 – 8 cm long, 8 – 15 mm wide, straight to shallowly curved, dehiscing along the dorsal suture, woody, conspicuously resinous, reddish brown, prominently nerved, the nerves broad, sharply defined, prominently raised – hence the reference to furrows in the specific name. The seeds are oblique, ovoid to obloid or ellipsoid, 3.5 – 5 mm long, 2 – 3 mm wide; the funicle/aril is 2 – 6 mm long (unextended).

The heartwood varies in colour from light brown to brown, often streaked with darker markings. The sapwood is creamy white to pale brown. The grain is variable, its texture coarse but fairly even. It is a moderately hard timber relating to ease of working with hand tools. It is relatively easy to machine, and turns to a smooth finish. Staining is usually not necessary, and the timber polishes and paints well. The timber formerly had limited use in general house framing, flooring, linings and mouldings, but is now rarely so used. Its current uses include the making of plywood, furniture, joinery, turning and walking sticks. It is sometimes used for tool handles, especially axes and hammers. The timber is very similar to Thick-podded Salwood and Black Wattle.

The inner bark can be used for tannin production. Nitrogen-fixing, the tree is a popular species in the reforestation of poor soils. It is sometimes planted as an ornamental.

This is a food plant for the larvae of the Geometridae moth Uliocnemis partita.

Photographs taken Horseshoe Bay 2011, Nelly Bay 2014
Page last updated 22nd September 2018