Common Name

Northern Star Wattle

Family

Fabaceae

Distribution

Occurs in north western and northern W.A. from Exmouth Gulf to near Broome and eastwards through the Great Sandy Desert and the extreme southern Kimberley region to the Tanami area in N.T.; recorded between 18º00'S and 23º30'S.

Description

Shrub 0.3–1.5 (–2) m high and wide, rounded or flat-topped, glabrous, resinous. Branchlets angular towards apices, pale green, brown or yellowish; ridges resin-crenulated. Phyllodes asymmetrically elliptic-obovate to narrowly elliptic-obovate or sometimes semi-orbicular, often slightly sigmoid, (0.5–) 0.8–2 (–2.5) cm long, (3–) 4–12 (–15) mm wide, slightly thickened, very finely longitudinally wrinkled when dry; apex with a small knob-like mucro; superficially nerveless or with 1–3 very indistinct longitudinal nerves slightly more evident than the rest; basal gland minute, to 2 mm above pulvinus. Peduncles (5–) 10–30 (–40) mm long, erect; heads 10–14 mm diam. when fresh, 7–25 (–45)-flowered, golden, flower buds normally large, wide-spreading and sub-acute. Flowers 5-merous; calyx cupular, 0.7–1.1 mm long, barely dissected; corolla usually 3´ longer than calyx, 2.4–3.5 mm long, dissected by 1/2–2/3; petals striated; ovary ±villous. Pods erect, narrowly elliptic to ±linear or linear-oblanceolate to narrowly oblanceolate, basally tapered, ±straight-sided, flat, mostly 2.5–10 cm long, 4–10 mm wide, thinly woody, scurfy, obliquely striate, opening elastically from apex, the dehisced valves strongly recurved; margins slightly thickened. Seeds oblique, oblong- to narrowly oblong-elliptic, 4–6 mm long, light to dark brown; pleurogram with pale halo; areole open, elongated, depressed; funicle-aril narrowly conical.

Phenology

Flowers Feb.–Sept.

Habitat

Grows in red, sometimes clayey sand over quartzite, limestone, laterite or ironstone, on hills or sandplains, often on flats between parallel sand dunes, in open savannah, scrub heath, grassland or shrubland, often with spinifex.

Specimens

W.A.: ‘Nita’, SW of Broome, F.Lullfitz 6222 & 6222a (NSW); near Well 24, Canning Stock Route, B.R.Maslin 2269 (PERTH, n.v. : CANB, K, MEL); 63.5 km N of Sandfire Roadhouse, B.R.Maslin 4880 (PERTH). N.T. (small flowered variant): 26 km S of Rabbit Flat turnoff on Tanami Track, D.Keith & B.Pellow 126 (DNA, NSW, PERTH, SYD).

Notes

Acacia sphaerostachya is most probably a hybrid between A. ancistrocarpa and A. stellaticeps. Putative hybrids between A. stellaticeps and both A. arida and A. trachycarpa have been reported from near Roebourne but these are very rare and have not been collected in recent years. In the extreme NW of the Pilbara A. stellaticeps appears to hybridize with A. hilliana (see A. hilliana × stellaticeps).

A small flowered variant occurs in the Sturt Creek area, W.A., to The Granites–Rabbit Flat area, N.T., and is characterised by smaller, more compact heads (5–7 mm diam.) often containing a larger number of flowers (up to 37 per head) which are usually smaller with a corolla 1.5–1.9 (–2.5) mm long, e.g. Wolf Creek Crater, A.S.George 15333 (DNA, PERTH), 21 miles [33.8 km] NW of Granites, N.T., J.R.Maconochie 999 (BRI, DNA, K, MEL, NSW, PERTH).

Related to Acacia sp. Kununurra (G.Lullfitz 6195) and A. translucens in the ‘A. stigmatophylla group’, but is distinguished by its prominently spreading, large flower-buds, often larger flowers with striated petals, and a ±erect knob-like to conical mucro on the phyllodes (the apical mucro is initially flattened against the lamina margin in the other species). The wide-spreading, tapered flower buds that impart a star-like appearance to the unopened heads of A. stellaticeps are similar to those of the more distantly related A. perpusilla and A. anserina.

FOA Reference

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

Author

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