Common Name

King Edward River Wattle

Family

Fabaceae

Distribution

Occurs in the northern Kimberley region of W.A. where it is known only from along the King Edward R. on Theda Stn, c. 30 km SW of Kalumburu.

Description

Spindly, erect, glabrous shrub to 2 m tall. Branchlets resin-ribbed. Stipules persistent, 1–2 mm long. Phyllodes widely obovate, dimidiate with upper margin prominently rounded and lower margin ±straight, 3–4 mm long (excluding mucro), 2–4 mm wide, mostly ascending to erect, apices excentrically mucronate with the often bristle-like, subulate mucro 0.5–1.5 mm long and straight to shallowly incurved; longitudinal nerves numerous, often indistinct, none anastomosing. Peduncles 4–12 mm long, resinous; heads globular, c. 15-flowered, the relatively large buds wide-spreading and narrowed towards their apices. Bracteole laminae triangular-trullate, light brown and distinctly acuminate. Flowers 5-merous; calyx 1/4–1/3 length of corolla, very shortly dissected into triangular lobes; petals 1-nerved. Pods linear, depressed-quadrangular in section when young, neither raised over nor constricted between the seeds, 3–7.5 cm long, 2–3 mm wide, ±thinly crustaceous to slightly coriaceous, opening elastically from apex, the dehisced valves recurved. Seeds longitudinal, seated in distinct chambers each separated by a narrow septum, obloid, c. 4 x 2 mm; funicle-aril conical, c. 2 mm long, straight, cream-coloured.

Phenology

The paucity of collections makes it difficult to determine the phenology; flowers collected May–July with the May specimen also possessing mature pods.

Habitat

Grows in shallow soil among sandstone outcrops along watercourse in association with Sorghum sp. and Heteropogon contortus.

Specimens

W.A.: [localities withheld for conservation reasons] R.Maher s.n. (G, MEL, NSW, NY, PERTH 08427771 & 08428867).

Notes

A member of the ‘A. stigmatophylla group’ seemingly closest to A. setulifera which is most readily distinguished by its phyllodes that are patent, ovate to elliptic, not markedly asymmetric and very indistinctly nerved; it also has broader pods and normally more numerously-flowered heads; see B.R.Maslin, M.D.Barrett & R.L.Barrett, Nuytsia 23: 574–575 (2013) for further discussion. Seemingly also close to A. anserina (which has hairy branchlets and phyllodes) and superficially similar to A. barrettiorum (which has broad-based, sessile, symmetrically oblong phyllodes).

The wide-spreading, tapered flower buds that impart a star-like appearance to the unopened heads of A. perpusilla and A. anserina are similar to those of A. stellaticeps, another member of the ‘A. stigmatophylla group’, but which has larger phyllodes with a small, thickened, erect, knob-like apical point.

Conservation

Acacia perpusilla is listed Priority One under Department of Parks and Wildlife Conservation Codes for Western Australian Flora.

FOA Reference

Flora of Australia Project

Author

B.R.Maslin