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Acacia leptocarpa Benth. 1842
pronounced: uh-KAY-shuh lep-toh-KAR-puh
(Mimosaceae – the wattle family)
synonym: Racosperma leptocarpum (Benth.) Pedley 1987
pronounced: rak-ow-SPER-muh lep-toh-KAR-pum
common name: Leptocarpa Wattle
Acacia is from the Greek ακις (akis), a thorn or spike; leptocarpa is from λεπτος (leptos), slender, and καρπος (karpos), fruit, referring to the slender pods. In the synonym, Racosperma is from 'ρακος (rhakos), rough, ragged, and σπερμα (sperma), a seed.
This wattle occurs in tropical Australia from Carlton Hill Station in the north of Western Australia, eastwards to Arnhem Land and the Gulf of Carpentaria, including offshore islands, to Cape York and southwards along the eastern Queensland coast to Bundaberg, at an altitudinal range from near sea level to 700 m. It usually grows in open forest, particularly Melaleuca woodlands, but is occasionally found on the margins of rainforest, vine thickets, beach forest and gallery forest. It is found in sandy or rocky soils, sometimes on laterite, and often on seasonally inundated plains. It also occurs in southern New Guinea.
Acacia leptocarpa varies from a single-stemmed shrub, 3 – 5 m tall, usually with a short main stem, to a small tree 12 – 15 m in height; the main trunk may be 4 m long and 25 cm in diameter. It is well-branched, and has a light to moderately dense crown. The branchlets and new shoots are glabrous, but the shoots are encrusted with a layer of brown resin. On large trees the bark is deeply furrowed, but on smaller stems it is thin and more-or-less tessellated.
The phyllodes are falcate, 12 – 26 cm by 1 – 3.5 cm, thinly textured, glabrous; the base attenuate and confluent with the lower margin; there are 3 prominent yellowish longitudinal veins with parallel and widely-spaced secondary veins. A gland may be visible on the upper margin surface of the leaf blade-petiole junction, but often it is not apparent. The petiole is somewhat swollen and longitudinally wrinkled. The stipules are very small and inconspicuous.
The flowers are pale yellow to bright yellow, pleasantly perfumed, sub-densely arranged in cylindrical spikes, 3.5 – 9.5 cm long, the spikes in groups of 2 – 5 within phyllode axils. There are some male flowers, and some bisexual.
The pods are linear, somewhat coiled, up to 12 cm by about 3 mm, flat, but raised over the seeds. The yellow-orange funicle is folded many times to form an aril-like structure that can be longer than the seed, but not encircling the seed. The seeds themselves are about 4 mm long, black, with the long axis parallel to the pod.
Acacia leptocarpa hybridizes with Acacia auriculiformis. In its natural range in Australia, flowering occurs between May and December, and the seeds mature October to December.
The wood of this species is used for fuel, posts and poles, small joinery and turned items, and cabinet work. The tree can provide moderate shade, and may be used as an ornamental.
This is a food tree for Jalmenus eichhorni, the Northern Imperial Blue butterfly.
Photographs taken in Nelly Bay 2012
Page last updated 3rd November 2017