Acacia mangium  Willd. 1806

pronounced: uh-KAY-shuh MANG-ee-um

(Mimosaceae – the wattle family)

common names:  Black Wattle, Broadleaf Salwood

Acacia acacia mangiumblack wattle acacia mangium phyllodecultivated treeis from the Greek ακις (akis), a thorn or spike. I have not been able to trace the derivation of mangium, although I suspect the word may be Indonesian or Malayan in origin.

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 is native to Australia, Indonesia, and PNG. It is also much planted as an exotic in Malaysia, South Africa, Thailand and Vietnam.

acacia mangiumfoliage acacia mangium phyllodephyllode In Australia, Acacia mangium occurs in Cape York Peninsula and north-east Queensland, widespread through the area. Its altitudinal range is from sea level to 750 m, and it grows in well-developed lowland and upland rainforest. The trees photographed are near the West Point Road, not far out of Picnic Bay, and (the cultivated one) in a Picnic Bay roadside garden.

Generally, the species is favoured by disturbance, being a rapid developer and a typical component of rainforest regrowth, particularly on the coastal lowlands. The tree had been severely damaged by cyclone Yasi, and seemed to be coming into flower much earlier in the year than usual, as compensation.

acacia mangium floweringflowering acacia mangium flower spikea flower spike This is a single-stemmed evergreen tree or shrub capable of growing to about 30 m high. Young trees have smooth greenish bark: fissures begin to develop at 2–3 years of age. The bark in older trees is rough, hard, fissured near the base, greyish brown to dark brown.

The bole in older trees grows branchless for up to 15 m, fluted, up to 90 cm in diameter, and the branchlets are acutely triangular.

The phyllodes are large, up to 25 cm long and from 3.5–10 cm broad. One side of the blade is almost straight, and the other more strongly curved. The veins are longitudinal, running together, 3 or 4 veins usually more prominent than the rest. Two veins adjacent to the straighter blade margin adhere to one another for quite a distance. A small gland is usually visible on the upper side of the blade-petiole junction.

detail of flowers seed pods forming The flowers are in rather loose spikes, up to 10 cm long. The calyx is about 0.6–0.8 mm long, with short obtuse lobes. The corolla is about twice as long as the calyx; the stamens are about 3–4  mm long, and the ovary densely pubescent.

The fruit pods are linear, coiled, 3–5 mm wide, membranous or slightly woody, depressed between the seeds. The seeds are shiny black, longitudinally oriented in the pod, and about 5 mm long.

This species has been used extensively in south-east Asia for reforestation.

mature seed pods seed pods It yields a useful timber. 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 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 Golden-flowered Salwood.

This is a host plant for the caterpillars of Prosotas dubiosa, (the Small Purple Line Blue butterfly).

Photographs taken in Picnic Bay , 2011, 2016

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