Tree, to 20 m tall, densely ferruginous-hirsute all over to sparsely so or glabrate on leaflet surface and sericeous on corolla. Rachis conspicuously winged; interfoliar glands stalked, to +/- 3 mm tall; leaflets in 3-5 pairs, ovate to elliptic, acute to caudate-acuminate, rounded to slightly cordate and asymmetrical at base, sometimes +/- bullate between veins, the terminal pair 11-24 cm long, 6-13 cm wide, usually with a gland on midrib above within 2 cm of base (sometimes obscured by pubescence); juvenile leaves less densely pubescent and to 80 cm long with the terminal leaflets to 42 cm long and 19 cm wide. Spikes axillary, usually solitary; peduncles 3-9 cm long, stout; rachis 10-20 cm long; bracts to 6 mm long; flowers sessile; calyx campanulate, 12-20 mm long, the lobes acute, 3-7 mm long; corolla campanulate, sericeous, 20-28 mm long, more than 8 mm wide; stamens and style to ca 50 mm; style sometimes persistent on growing legume. Legumes flat or twisted, 10-25 cm long, 4-6 cm wide, to 1.5 cm thick, densely ferruginous-hirsute; valves splitting open (usually from bottom) at maturity to expose seeds; seeds oblong, to 1.8 cm long, not colorful. Croat 8300, 13107. Occasional, in the forest. Flowers mostly from November to February. The fruits probably mature in the rainy season. Similar to I. mucuna, but distinguished by the short corolla, more reddish-brown fruits, and the gland on the midrib of the leaflet above.