Common Name

Karroo Thorn

Family

Fabaceae

Distribution

Native to large parts of southern Africa. Formerly naturalized near Perth, W.A. (now eradicated) and occurred in a small area on the Darling Downs, Qld (now eradicated but subject to ongoing surveillance); also recorded from vacant land in Newcastle, N.S.W.

Description

Multi-stemmed shrub or (according to J.H.Ross, loc. cit.) a tree to 12 (–20) m high, crown ±rounded or flat-topped. Bark brown to black and rough or greyish and smooth. Branchlets glabrous, dark brown, lenticellular. Stipular spines 5.5–12 cm long, rigid, patent, straight, terete, white. Leaves arising from within axil of spines and also from branch immediately above spines, sometimes grouped 2 or 3 together; petiole 5–10 mm long, channelled above, glabrous, with a quite prominent gland (1–1.5 mm long) on adaxial surface near base; rachis 15–30 mm long, glabrous, channelled above, with a small gland at base of pinnae; pinnae 2–3 pairs, (15–) 20–40 mm long; pinnules 6–12 pairs, narrowly oblong to oblong-oblanceolate, 3.5–8 mm long, 1–2.5 mm wide, glabrous, green, concolorous, obscurely 1-nerved, sometimes with small gland at base of some pairs. Inflorescences (based on J.H.Ross, loc. cit.) single or fascicled; peduncles 7–24 (–40) mm long, with involucel of bracts 1/3–3/4 from the base; heads globular, bright yellow. Pods (based on J.H.Ross, loc. cit.) linear, ±constricted between the seeds, often distinctly moniliform, (4–) 5–1.5 (–21) cm long, 5–7 (–11) mm wide, dehiscent, normally curved, longitudinally nerved, glabrous or sometimes tomentulose.

Specimens

Qld: ‘Condamine Plains’, c. 20 km N of Pampas on Cecil Plains Rd, May 2008, P.Hodgson s.n. (BRI 783604). N.S.W.: Carrington, in vacant ground within the industrial area of Newcastle, 7 Oct. 1969, J.M. Turnbull s.n. (NSW149784).

Notes

Based on molecular and other data Acacia sens. lat. is now considered as comprising a number of segregate genera, see J.T.Miller & D.S.Seigler, Austral. Syst. Bot. 25: 217-224 (2012) for overview. Many taxa in the former Acacia subg. Acacia are now referable to the genus Vachellia, including the one presented here.

This species is comprehensively described in J.H.Ross, loc. cit.

Unless otherwise stated the above description is based on the few sterile specimens in Australian herbaria.

FOA Reference

Flora of Australia Project

Author

B.R.Maslin