Polygonum amphibium L., Sp. Pl. 361. 1753; Hook. f., Fl. Brit. Ind. 5: 34. 1886; Rech.f. & Schiman-Czeika in Rech.f., Fl. Iran. 56: 56. 1968; R.R.Stewart, Ann. Cat. Vasc. Pl. W. Pak. & Kashm. 203. 1972; Bhopal & Chaudhri in Pak. Syst. 1(2): 76. 1977; Polygonum amphibium var. natans Leyss., Fl. Hall. 391. 1761; var. terrestre Leyss. l.c.; Polygonum pusporium Gilib. Exerc. Phytol. 2: 433. 1792; Polygonum amurense Niewalnd in Amer.Midl. Nat. 2: 183. 1821; Persicaria amphibia (L.) S. F. Gray var. natans (Leyss.) Munshi & Javeid, l.c. 63 and var. terrestre (Leyss.) Munshi & Javeid, l.c.

Erect, 30-80 cm tall, floating or submerged (amphibious), perennial herb. Stem floating, submerged or aerial, glabrous or sometime covered with stiff hairs, rooting at the nodes. Leaves 6-12 x 2-4 cm, elliptic-lanceolate or oblong, obtuse-acute, truncate or subcordate at base, petiolate or subsessile, petiole 4-10 cm long. Ochreae 10-20 mm long, truncate, glabrous or rarely sparsely ciliate-hispid. Inflorescence densely flowered, conical, 8-30 mm long, solitary raceme. Ochreolae 1-2 x c. 1 mm, ovate. Flowers pedicellate. Tepals 5, biseriate, bright red or pink, 2-2.5 x 1.5-2 mm narrowly elliptic. Stamens 5, exerted. Ovary oval, 1.3-2 mm long, with inserted or exserted styles, styles 2, 2-4 mm long, free, stigma capitate. Nuts 2.5-3.3 x 1.5-2.0 mm, ovoid or orbicular, shining, dark brown, inserted or slightly exerted with the base of style forming a persistent beak.

Fl. Per.: June-September.

Type: Described from Europe, Hb. Linn. 510/7 (LINN).

Grows between 800-4500 m; Distribution: Europe, W. Asia, Himalayas (Pakistan, Kashmir to Bhutan), Xizang, Siberia, China, Japan and North America.

A variable species, sometimes different varieties are recognized on the basis of aerial and floating stems. However, this variation seems to be correlated with the habitat and several intermediate forms are also met with.