Description from
Flora of China
Persicaria amphibia (Linnaeus) S. F. Gray; P. amphibia var. terrestris (Leysser) Munshi & Javeid; P. amurensis (Korshinsky) Nieuwland; P. muhlenbergii (Meisner) Small; Polygonum amphibium var. amurense Korshinsky; P. amphibium var. muhlenbergii Meisner; P. amphibium var. natans Michaux; P. amphibium var. terrestre Leysser; P. amphibium var. vestitum Hemsley.
Herbs perennial, amphibious. Rhizomes horizontal. Aquatic plants: stems floating, glabrous, rooting at nodes; leaves long petiolate, floating; leaf blade oblong or elliptic, 5-12 × 2.5-4 cm, glabrous, base subcordate, margin entire, not ciliate, apex obtuse or slightly acute; ocrea tubular, thinly membranous, apex truncate, not ciliate. Terrestrial plants: stems erect, 40-60 cm tall, simple or branched at base. Petiole 3-5 mm; leaf blade lanceolate or oblong-lanceolate, 6-14 × 1.5-2 cm, both surfaces appressed-hispidulous, base rounded, margin entire, ciliate, apex acute; ocrea tubular, 1.5-2 cm, membranous, sparsely hirsute, apex truncate, shortly ciliate. Inflorescence terminal or axillary, spicate, 2-4 cm; bracts broadly funnel-shaped. Perianth pinkish or white, 5-parted; tepals oblong, 3-4 mm. Stamens usually 5, included. Styles 2, exserted, connate to middle; stigmas capitate. Achenes included in persistent perianth, black, shiny, orbicular, biconvex, 2.5-3 mm in diam. Fl. Jul-Aug, fr. Aug-Sep. 2n = 66, 96.
In ponds, riverbanks, wet fields, waste areas; sea level to 3700 m. Anhui, Gansu, Guizhou, Hebei, Heilongjiang, Henan, Hubei, Hunan, Jiangsu, Jilin, Liaoning, Nei Mongol, Ningxia, Qinghai, Shaanxi, Shandong, Shanxi, Sichuan, Xinjiang, Xizang, Yunnan [Very widely distributed: Bhutan, NW India, Japan, Kashmir, Kazakhstan, Korea, Kyrgyzstan, Mongolia, Nepal, Russia, Tajikistan, Turkmenistan, Uzbekistan; Asia, Europe, North America].