Evergreen shrub or small tree up to 6 m high, with slender often pendulous branches. Petiole and leaf-rhachis very short, produced into a straight well-developed spine, with 1–3 pairs of long flattened pinnae-rhachides; leaflets many, opposite to alternate, oblong-elliptic to obovate, 2–7 x 1–2.5 mm, glabrous. Racemes lax, up to 20 cm long. Sepals 6–7 mm long. Petals yellow, ovate-rhombic, 8–12 x 6–8 mm; upper one marked red, with more rounded blade and longer claw. Pod constricted into oblong or elliptic segments, pointed or beaked, c. 3–15 x 0.6–0.8 cm; valves coriaceous, diagonally striate, eventually separating along upper suture. Seeds oblong-ellipsoid, 7.5–10 x 3.5–4 mm, brownish, sometimes mottled.
Range
Cultivated for ornament, shade and wind-breaks at least in N1, C1, S1, S2 and S3, and sometimes naturalised native of tropical and subtropical America.
