An exceedingly variable species. Tree (1.2–) 2.5–14 m. high; bark on trunk rough, fissured, blackish, grey or brown, neither powdery nor peeling. Young branchlets from almost glabrous to subtomentose; glands inconspicuous or absent; bark of twigs not flaking off, grey to brown. Stipules spinescent, up to 8 cm. long, straight or almost so, often ± deflexed; “ant-galls” and other prickles absent. Leaves often with 1(–2) petiolar glands and others between all or only the topmost of the 2–11 pairs of pinnae; leaflets 7–25 pairs, 1.5–7 mm. long, 0.5–1.5 mm. wide, glabrous to pubescent; lateral nerves invisible beneath. Flowers bright yellow, in axillary pedunculate heads 6–15 mm. in diameter; involucel from near base to about halfway up peduncle. Calyx 1–2 mm. long, subglabrous to pubescent. Corolla 2.5–3.5 mm. long, glabrous to ± pubescent outside. Pods especially variable, indehiscent, straight or curved, glabrous to grey-velvety, ± turgid, (4–) 8–17(–22) cm. long, 1.3–2.2 cm. wide. Seeds deep blackish-brown, smooth, subcircular, compressed, 7–9 mm. long, 6–7 mm. wide; areole 6–7 mm. long, 4.5–5 mm. wide.
