Acacias of Australia

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Acacia undoolyana G.J.Leach

Common Name

Sickle-leaf Wattle, Undoolya Wattle




Restricted to the East MacDonnell Ra., N.T., from N’Dhala Gorge (c. 65 km E of Alice Springs), Kadaicha Ra. and 25 km SW of Trephina Gorge.


Shrub or tree 1–15 m high. Bark flaky or fissured, greyish brown. Branchlets terete, appressed pubescent or glabrous, rarely lightly pruinose, obscurely ribbed. New shoots silvery or very pale yellow sericeous. Phyllodes narrowly elliptic, normally markedly falcate, 15–22 cm long, (4–) 6–12 (–16) mm wide, with conspicuous yellowish margins, coriaceous, stiff, silvery-velvety when young, later sparsely pubescent and with dense white scurfy bloom; finely multistriate, with 1–3 nerves more prominent, not visibly anastomosing; gland basal, inconspicuous. Inflorescences short, (1–) 2 (–4)-branched racemes 1–10 (–15) mm long which often grow out; peduncles 3–6 mm long, densely appressed pubescent; spikes, 1.3–3.5 (–5) cm long, dense, bright yellow. Flowers 5-merous; calyx 0.7–1 mm long, dissected to 1/4–1/5, pubescent especially on ribs, with obtuse lobes; corolla twice as long as calyx, dissected to 1/2, glabrous. Pods linear, raised over and constricted between seeds, 5–11 cm long, 2–3 mm wide, sparsely pubescent. Seeds longitudinal, oblong, 3–4.5 mm long, brown.


Flowers Aug. & Sept.; fruits Sept. & Oct.


Grows on steep rocky slopes with skeletal soils or at the base of sandstone gullies.


N.T.: N’dala [N’dhala] Gorge, 15 Oct. 1966, A.C.Beauglehole. (DNA); Ndala [N’dhala] Gorge Scenic Reserve, 16 Aug. 1987, L.D.Meredith et al. (CANB n.v., MEL n.v., NSW); Kadaicha Ra., A.Soos 24 to 27 (DNA).


Closely allied to A. macdonnellensis, being distinguished by its strongly falcate phyllodes which are longer (15–22 cm), broader (6–12 mm) and silvery when fresh. It is also related to A. ammobia which has glabrous peduncles, mostly straight phyllodes and occurs on sand dunes.

FOA Reference

Data derived from Flora of Australia Volumes 11A (2001), 11B (2001) and 12 (1998), products of ABRS, ©Commonwealth of Australia


Dr M.D.Tindale and Dr P.G.Kodela with the assistance of M.Bedward, S.J.Davies, C.Herscovitch, D.A.Keith and/or D.A.Morrison