Acacias of Australia

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Acacia undosa R.S.Cowan & Maslin




Known only from scattered localities from near Tammin and Bruce Rock S to Lake Grace and SE to near Lake King in south-western W.A.


Dense, domed or obconic shrubs 0.3–1.5 m high. Branchlets tomentulose. Stipules persistent, ±subulate, to 2 mm long. Phyllodes spreading, linear to linear-oblanceolate, straight to shallowly incurved, 2–4.5 cm long, 1–4 mm wide, obliquely mucronate to subuncinate with a hard innocuous to coarsely pungent point, rarely with a straight sharply pungent point, rigid, glabrous except pulvinus tomentulose, with ±9 plane or slightly impressed close nerves per face (20 nerves in all) with very occasional anastomoses; internerve spaces with strongly raised stomata; glands 1 or 2. Inflorescences simple, 2 per axil; peduncles 1–1.5 mm long, glabrous; basal bracts cucullate, rostrate; heads globular, 3–3.5 mm diam., 18–20-flowered, golden. Flowers 5-merous; sepals free or to 1/2-united. Pods linear, strongly undulate, 1–4 cm long, 2.5 mm wide, crustaceous, papillous; marginal nerve distinct, much paler. Seeds longitudinal, elliptic-oblong to broadly oblong-elliptic, 2.2–2.7 mm long, dark brown; aril apical.


Grows in clayey sand or loam in open shrub mallee.


W.A.: c. 0.4 km S of Belka Siding between Bruce Rock and Merredin, B.R.Maslin 1768 (AD, BRI, MO, PERTH); 36 km E of Lake King, K.Newbey 9476-1 (MEL, MELU, PERTH); 35 km S of Hyden towards Newdegate, R.Perry 545 (PERTH).


Several collections made between Tammin to c. 110 km NE at Warralakin (e.g. Survey camp, N of Warralakin, J.S.Beard 4735, PERTH) have 1/2-united sepals but in all other respects are referrable to this species.

A member of the ‘A. densiflora group’ similar in several characteristics to A. hadrophylla. Specimens with very narrow phyllodes sometimes resemble A. densiflora but that species has tomentulose peduncles and non-undulate pods.

FOA Reference

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