24. Polygonum persicaria Linnaeus, Sp. Pl. 1: 361. 1753.
Herbs annual. Stems erect or ascending, 40-80 cm tall, branched or simple, sparsely pubescent or glabrescent. Petiole 5-8 mm, appressed hispidulous; leaf blade lanceolate or elliptic, often with a dark triangular spot at middle, both surfaces appressed hispidulous, densely so along midvein, base narrowly cuneate, margin largely ciliate, apex acute or acuminate; ocrea tubular, 1-2 cm, membranous, sparsely pubescent, apex truncate, cilia 0.4-3 mm. Inflorescence terminal or axillary, spicate, 2-6 cm, usually several spikes aggregated and panicle-like; peduncle glandular hairy or glabrous; bracts funnel-shaped, ciliate, each 5-7-flowered. Pedicel 2.5-3 mm. Perianth reddish or deep purple, usually 5-parted; tepals oblong, 2.5-3 mm, distinctly veined. Stamens 6 or 7. Styles 2, rarely 3, connate to below middle. Achenes included in persistent perianth, black-brown, shiny or opaque, suborbicular or broadly ovoid, biconvex, rarely trigonous, 2-2.5 mm, smooth. Fl. Jun-Jul, fr. Jul-Sep. 2n = 22, 42.
Streamsides, wet areas, field margins; 100-1800 m. Anhui, Fujian, Gansu, Guangxi, Guizhou, Hebei, Heilongjiang, Henan, Hubei, Hunan, Jiangxi, Jilin, Liaoning, Nei Mongol, Ningxia, Qinghai, Shaanxi, Shandong, Shanxi, Sichuan, Taiwan, Xinjiang, ?Yunnan, Zhejiang [Indonesia, Japan, Kazakhstan, Korea, Kyrgyzstan, Russia, Tajikistan, Turkmenistan, Uzbekistan; Africa, Europe, North America].