蝶豆 die dou

Herbs. Stems twining, slender, densely deciduous ad­pressed shortly villous. Leaves 2.5-5 cm, pinnately 5-7-folio­late, usually 5-foliolate; stipules small, linear, 2-5 mm; petiole 1.5-3 cm; stipels small, bristlelike; petiolules 1-2 mm; leaflets broadly elliptic or almost ovate, 2.5-5 × 1.5-3.5 cm, thinly pa­pery or almost membranous, adpressed shortly villous or some­times glabrous on both surfaces, lateral veins 4 or 5 pairs, base obtuse, apex obtuse, slightly emarginate, usually with mucro. Flowers large, solitary in axil; bracteoles green, small, subor­bicular or obovate, membranous, with obvious reticulate veins. Calyx membranous, 1.5-2 cm, 5-lobed; lobes lanceolate, less than 1/2 of tube, apex acuminate. Corolla sky blue, pink, or white, to 5.5 cm; standard faintly white or orange in middle, broadly obovate, ca. 3 cm, base shortly clawed; wings and keels much shorter than standard, both clawed; wings obovate-ob­long; keels elliptic. Ovary villous. Legume brown, linear-ob­long, 5-11 × 0.7-1 cm, compressed, with long beak. Seeds 6-10, black, oblong, ca. 0.6 × 0.4 cm, with obvious strophiole. Fl. and fr. Jun-Nov. 2n = (14, 15), 16.

Fujian, Guangdong, Guangxi, Hainan, Taiwan, Yunnan, Zhejiang [Bangladesh, Bhutan, Cambodia, India, Indonesia, Laos, Ma­laysia, Myanmar, Nepal, Pakistan, Papua New Guinea, Philippines, Singapore, Sri Lanka, Thailand, Vietnam; Africa, Americas, SW Asia, Australia, In­dian Ocean islands, Pacific islands].

This species is grown as a green manure and as an ornamental. It is very widely distributed throughout the tropics such that the native dis­tribution is now obscure.