Corolla deciduous; standard lemon-yellow, 8–13 × 8–10 mm, obovate, with claw 1.5–2 mm long, the blade with a thickened somewhat lobed callous protuberance at its base.
Calyx glabrous save at the margin, receptacle cup (hypanthium) 2 mm long; calyx tube c. 2–3 mm long, the upper lobes 3 mm long, lateral lobes 3–4 mm long, triangular, lower lobe folded, 5 mm long, lanceolate, acuminate.
Seeds buff, 5.5 × 3 × 1.2 mm, very compressed ellipsoid with almost keeled margin.
Fruit brownish, usually of 3 articles and 3.5 cm long, longitudinally and reticulately ribbed; stipe 2–3 mm long or appearing much longer when basal article does not develop, articles up to 16 × 8 mm, 2 mm thick, shortly and rather sparsely pubescent with stiff hairs c. 0.3 mm long, many of them with minutely tubercular bases and glandular.
Shrub 1–3 m tall; branchlets at first purplish, later whitish, sparsely pubescent with both white and swollen-based hairs; bark on older stems eventually splitting longitudinally.
Leaves single or fasciculate; leaflets 9–17, (3)8–20 × (1.5)3–9 mm, elliptic-oblong, shortly mucronate, slightly cordate at the base, the margins revolute, sparsely appressed white pubescent beneath; lateral nerves and midrib dark purplish or brownish beneath; petiole 2–5 mm long; rhachis 2–5.5 cm long, pubescent and with swollen-based hairs; stipules up to 7 mm long, narrowly triangular, long drawn out to a fine tip.
Racemes c. 10–15 mm long, mostly 2-flowered; peduncles very short; pedicels 4–15 mm long, glabrous or pubescent; bracts c. 5 per inflorescence, 2–3 mm long, ovate-lanceolate, acuminate; bracteoles similar, c. 4 mm long, 2–4 mm below the receptacle.
Twigs at first purplish, later whitish, sparsely pubescent with both white and swollen-based hairs, the bark finally splitting longitudinally.
Leaves single or in tufts; stipules narrowly triangular with long attenuate tips, up to 7 mm. long; rhachis with both white and swollen-based hairs, 2.5–6 cm. long, including the petiole of 2–5 mm.; leaflets 9–17, elliptic-oblong, 8–20 mm. long, 3–9 mm. wide, shortly mucronate, revolute at the margin, sparsely appressed white pubescent beneath; lateral nerves, like the midrib, dark purplish beneath, much wider and more conspicuous than those of O. sennoïdes.
Axis of inflorescence up to 15 mm. long, bearing up to 5 bracts but rarely more than 2 flowers; bracts lanceolate-acuminate, 2–3 mm. long; bracteoles similar, up to 4 mm. below receptacle; pedicels 4–15 mm. long, pubescent or nearly glabrous.
Calyx glabrous except at the margin; receptacle-cup 2 mm. deep, 3.5 mm. long and 2.5 mm. wide; tube ± 1.5 mm. deep; upper lobes 3 mm. long; lateral lobes ovate-acuminate, acute, 4 mm. long; lower lobe lanceolate-acuminate, folded, very acute, 5 mm. long.
Pod with a stipe of 2–3 mm. hidden in the persistent calyx, shortly and sparsely pubescent, the hairs stiffly erect up to 0.3 mm. long, some of them springing from minute tubercles ± 0.1 mm. in diameter; segments up to 16 mm. long, 8 mm. wide and 2 mm. thick.
Corolla caducous, strongly veined, the standard burnt yellow becoming chestnut when dead, wings and keel pale lemon yellow; claw of standard 1.5 mm. long, blade ovate, 8–13 mm. long, 8–10 mm. wide, with a thick callous shelf-like somewhat lobed protuberance at the base; claw of wing 2.5 mm. long, blade narrowly obovate, 8 mm. long, 4 mm. wide; claw of keel 3.5 mm. long, blade 6 mm. long, 2 mm. wide at the base, 5 mm. near the apex.
Stamens (5) + (5), the united part 6–7 mm., free parts 3–5 mm., anthers 1.3 mm. long.
Tubular disc ribbed, undulate at the margin, 1.4 mm. long.