Description from Flora of China
?Mucuna coriocarpa Handel-Mazzetti; M. japonica Nakai; M. mairei H. Léveillé.
Woody vines, up to 25 m. Old stems over 30 cm in diam., young stems glabrous or rarely with sparse stiff pale hairs. Leaves 20-40 cm; petiole 7-16.5 cm, glabrous or with sparse hairs like stem; stipels not persistent; leaflets papery or thicker textured, glabrous or with fine pale stiff hairs, lateral veins 4 or 5 pairs, gently curved; terminal leaflet elliptic or elliptic-ovate, 8-15(-19) × 3.5-9 cm, base slightly cuneate, apex acuminate to 15 cm; lateral leaflets 7-14 cm, width ratio of abaxial to adaxial halves 1.25-1.5:1, abaxial half with base often truncate or slightly cordate. Inflorescences usually on old stems, 10-36 cm, with 5-10 nodes throughout length; bracts caducous, narrowly obovate, ca. 1.5 mm long and wide; bracteoles ovate or obovate, caducous; pedicels 1-2.5 cm, with stiff dark short adpressed hairs. Calyx with dense adpressed hairs on both sides and sparse caducous bristles outside; tube 8-12 × 18-25 mm; lateral lobes 5-8 mm, equaling lowest lobe or almost so, broadly triangular, upper lip often equaling lateral lobes. Corolla deep purple, black after drying; standard 3.2-4 cm; wings rather wide, 4.8-6 × 1.8-2 cm; keel 6-7 cm. Legume linear, straight or slightly curved, 30-60 × 3-3.5 cm, 1-1.3 cm thick, woody, with dense short fine red-brown hairs and sparse caducous reddish brown bristles, surface with conspicuous irregularly reticulate patterning, margins and surface constricted between seeds, base often with abrupt narrow neck, margin thickened into a well-defined smooth rounded ridge running along suture without a wing or median groove, apex acute. Seeds 4-12, shiny red, brown, or black, oblong or discoid, 2.2-3.2 × 2-2.8 cm, ca. 1 cm thick; septum woody; hilum black, length ca. 3/4 of seed circumference. Fl. Apr-May, fr. Aug-Oct. 2n = 22, 44.
Mucuna sempervirens is easily distinguished in flower from most other species with large purple flowers by its leaves without persistent stipels. It is often confused in fruit with M. macrocarpa, which differs by its legume without a distinct rounded margin and with a coarser surface patterning, its bicolored flowers with pubescent apex, and its leaves often with reddish hairs. Mucuna calophylla also lacks persistent stipels but has much smaller flowers and fruit and has leaves usually densely silky hairy abaxially.
This species is used medicinally and for paper-making, starch, and oil.
Forests, thickets, riversides; 300-3000 m. Fujian, Guangdong, Guangxi, Guizhou, Hubei, Hunan, Jiangxi, Shaanxi, Sichuan, Yunnan, Zhejiang [Bhutan, NE India (W Bengal, Manipur, Sikkim), Japan, Myanmar].