Glabrous or almost glabrous, vigorous, perennial liane. Leaflets usually in 3 pairs, including basal pair, petiolulate; tendrils branched and becoming woody towards base, purplish when young. Lamina 4-12 × 2-5.5 cm, elliptic to obovate, entire; base cuneate to rounded, sometimes asymmetric; apex acute or mucronate. Calyx accrescent, 3-4 × 1.7-2.7 cm; lobes broadly oblong or oblong-ovate to almost orbicular, glaucous, often purple-tinged where exposed to sunlight, mucronate; margins strongly undulate. Corolla 6-7 cm long, deeply campanulate, green, becoming purple after anthesis; tube c. 3 cm wide; lobes 1.5-2 cm long, broad and rounded. Filaments slender, with basal woolly tuft; anthers 10-12 mm long, linear. Capsule (3)-5.5-8.5 cm long, ± ellipsoid; valves 2-3 cm wide. Seed 1-1.5 cm long including narrow wing, broad- or oblong-ovoid.