Acacia heterochroa Maslin, Nuytsia 10: 93 (1995)
Glabrous shrub 0.5–1.5 m high. Branchlets terete, ribbed, normally ±lightly pruinose. New shoots, young peduncles and buds reddish. Stipules caducous. Phyllodes elliptic to ±ovate, ±obovate or almost circular (subsp. heterochroa ), or inequilaterally obtriangular to obdeltate (subsp. robertii ), 1–3.5 cm long, 1–2.5 cm wide, ±undulate, with ±pungent and 1 - 3 mm long apical point, ±coriaceous, grey-green to subglaucous; midrib and marginal nerves prominent; lateral nerves normally not evident; gland insignificant, 0–10 mm above base. Inflorescences simple or short-racemose; peduncles 5–25 mm long; heads globular, large, loosely 5–12-flowered, bright lemon yellow. Flowers 4-merous; sepals 1/5–1/4 length of corolla, united into a truncate to sinuolately lobed calyx. Pods erect, linear, curved, to 6.5 cm long, 3–4 mm wide, coriaceous-crustaceous to subwoody, purplish red and slightly pruinose when young, drying black except for the thick, undulate margins. Seeds (subsp. heterochroa ) longitudinal, oblong, 3.5–4 mm long, glossy, brown; aril terminal.
Occurs in the Ravensthorpe and Holt Rock districts, south-western W.A.
A member of the ‘ A. myrtifolia group’. Two allopatric subspecies are recognised.
Peduncles all or mostly single within axils of phyllodes; heads 8–12-flowered; phyllodes usually broadest near the middle
Peduncles all or mostly in racemes 10–35 mm long; heads 5–6-flowered; phyllodes broadest above the middle
Acacia heterochroa Maslin subsp. heterochroa
Phyllodes elliptic with some tending obovate or ovate, sometimes broadly elliptic or almost circular, 1.5–3.5 cm long, 1–2.5 cm wide, with apical point ±pungent. Peduncles 1–2.5 cm long, normally single in axils of reduced phyllodes on upper portion branchlets, sometimes a few interspersed in short racemes 5 - 17 mm long; heads 8–12-flowered.
Common in the Ravensthorpe Ra. from Mt Short SE to the vicinity of Elverdton Mine (c. 15 km SE of Ravensthorpe), with several outlying populations about 20 - 30 km E and 40 km N of Ravensthorpe. Grows in a variety of habitats but commonly in gravelly sand, laterite or rocky clay or clayey sand, on ridgelines or moderately exposed gentle slopes, in tall dense to low open mallee scrub with a dense sclerophyllous understorey.
Resembling A. durabilis with which it is often sympatric in the Ravensthorpe Ra., but A. durabilis is recognised by its more prominently ribbed branchlets, prominent, persistent stipules, phyllodes with a prominent gland generally closer to the base and an inflexed, less pungent tip, cream to pale yellow flower-heads, ±spirally twisted pods which do not have undulate margins and seeds with funicles that are dilated at the point of attachment to the pod.
Type of accepted name
Northern end of Ravensthorpe Ra., SE of Mt Short, W.A., 30 Aug. 1980, B.R.Maslin 4766 ; holo: PERTH; iso: CANB, K, PERTH.
W.A.: 40 km due N of Ravensthorpe, K.L.Bradby 90 (PERTH), 21.25 km S of Coujinup Hill, M.A.Burgman & S.McNee MAB 2009 (PERTH), Mt Desmond, c. 11 km S of Ravensthorpe, B.R.Maslin 2568 (K, PERTH); road to Mt Short, R.A.Saffrey 375 (AD, BRI, MEL, NY, PERTH); 4 km SE of Ravensthorpe on hill 1 km E of main road to Hopetoun, P.G.Wilson 5519 (NSW, PERTH).
Acacia heterochroa subsp. robertii Maslin, Nuytsia 10: 95 (1995)
Phyllodes inequilaterally obtriangular to obdeltate (adaxial margin with conspicuous rounded angle above the middle), 1–2.5 cm long, 1–1.5 cm wide, with apical point sharply pungent. Peduncles 0.5–1 cm long, in 2–8-headed racemes 1–3.5 cm long; heads 5–6-flowered.
Scattered in a restricted area in the Holt Rock district, c. 100 km N of the typical subspecies. Grows in lateritic gravel, in woodland or heath.
W.A.: Timber Reserve n. 20342, K.J.Atkins 1820 (CANB, K, PERTH); Holt Rock, A.Dirusse 2 (PERTH); Varley, 8 km E of Rabbit Proof Fence on Carstairs Rd, M.Pieroni 90/2 (PERTH).