Plants annual, 2-18 dm; roots also rarely arising from basal nodes; rhizomes and stolons absent. Stems ascending to erect, rarely decumbent, branched, ribbed, glabrous or appressed-pubescent to spreading-pubescent distally, stipitate-glandular or, rarely, without stipitate-glands. Leaves: ocrea brownish, cylindric, 6-20 mm, chartaceous, base inflated, margins truncate, eciliate or ciliate with bristles to 1 mm, surface glabrous or scabrous proximally, eglandular; petiole 0.1-1.5(-2.3) cm, glabrous or appressed-pubescent; blade sometimes with dark triangular or lunate blotch adaxially, linear-lanceolate to ovate-lanceolate, 2.3-13(-18) × (0.4-)1-2.3 cm, base tapered to cuneate, margins antrorsely scabrous, apex acute to acuminate, faces glabrous or appressed-pubescent along midveins, glandular-punctate abaxially. Inflorescences terminal and axillary, erect, uninterrupted, 8-60 × 10-18 mm; peduncle 8-60(-70) mm, glabrous or pubescent, usually stipitate-glandular; ocreolae overlapping, margins eciliate or ciliate with bristles to 0.8 mm. Pedicels ascending, 1.5-5 mm. Flowers 2-11 per ocreate fascicle, heterostylous; perianth pink, glabrous, not glandular-punctate, accrescent; tepals 5, connate ca. 4- 3 their length, obovate to elliptic, 3-4.6 mm, veins prominent, not anchor-shaped, margins entire, apex obtuse to rounded; stamens 6-8, included or exserted; anthers pink or red, elliptic; styles 2(-3), included or exserted, connate at bases. Achenes included or apex exserted, brownish black to black, discoid or, rarely, 3-gonous, 1 side usually slightly concave and other with central hump, (2-)2.2-2.9 × 2-2.8(-3) mm, shiny, smooth.
Polygonum bicorne Rafinesque, Fl. Ludov., 29. 1817; Persicaria longistyla (Small) Small; Polygonum longistylum Small