Description from Flora of China
Persicaria biconvexa (Hayata) Nemoto; Polygonum hastatotrilobum Meisner var. lenticulare Danser; P. thunbergii Siebold & Zuccarini f. biconvexum (Hayata) Liu et al.; Truellum biconvexum (Hayata) Soják.
Herbs annual. Stems ascending, prostrate at base, 30-80 cm tall, branched, retrorse prickly along angles. Petiole 2-4 cm, often narrowly winged, retrorsely prickly; leaf blade hastate, both surfaces bristly, sparsely shortly stellate hairy, base nearly truncate to cordate, margin ciliate; middle lobe broadly elliptic or ovate, usually contracted near base, margin ciliate, apex acuminate; basal lobes ovate, small, apex acute to obtuse; ocrea tubular, 5-10 mm, apex truncate, sometimes apex with herbaceous wing, ciliate. Inflorescence terminal or axillary, capitate; peduncle glandular hairy; bracts lanceolate, 3.5-4 mm, apex acuminate, ciliate, each 2-flowered. Pedicels shorter than bracts, 2-3 mm. Perianth pinkish, 4-parted; tepals elliptic, 2.5-3.5 mm, apex obtuse. Stamens 5 or 6, in 2 whorls. Styles 2, connate to below middle; stigmas 2, capitate. Achenes included in persistent perianth, brown, opaque, broadly ovoid, biconvex, ca. 3 mm. Fl. Jul-Aug, fr. Sep-Oct.
Slopes, forest margins, wet ditches; 1500-2500 m. Taiwan [Indonesia (Sumatra)].