蔓首乌 wan shou wu

Polygonum convolvulus Linnaeus, Sp. Pl. 1: 364. 1753; Bilderdykia convolvulus (Linnaeus) Dumortier; Fagopyrum convolvulus (Linnaeus) H. Gross; Helxine convolvulus (Linnaeus) Rafinesque; Reynoutria convolvulus (Linnaeus) Shinners; Tiniaria convolvulus (Linnaeus) Webb & Miquel.

Herbs annual. Stems twining, to 1-1.5 m, striate, papillate, branched at base. Petiole 1.5-5 cm; leaf blade small papillose abaxially, base cordate, margin entire, apex acuminate; ocrea short, membranous, oblique, not ciliate. Inflorescence axillary, racemose, interrupted; bracts narrowly ovate, apex acute, each 2-4-flowered. Pedicels longer than bracts, slender, margin white; tepals narrowly elliptic, unequal in size, outer 3 larger and keeled or narrowly winged on abaxial surface, slightly accrescent in fruit. Stamens 8. Styles 3, very short, stipitate. Achenes included in persistent perianth, black, opaque, ellipsoid, trigonous, 3-4 mm, finely granular. Fl. May-Aug, fr. Jun-Sep.

Thickets in valleys, stream banks; 100-3600 m. Anhui, Gansu, Guizhou, Hebei, Heilongjiang, Henan, Hubei, Jiangsu, Jilin, Liaoning, Nei Mongol, Ningxia, Qinghai, Shaanxi, Shandong, Shanxi, Sichuan, Taiwan, Xinjiang, Xizang, Yunnan [Widely distributed: Afghanistan, Bhutan, India, Japan, Kazakhstan, Korea, Mongolia, Nepal, Pakistan, Russia; Europe; introduced in North America].