Description from Flora of China
Polygonum humifusum f. yamatutae (Kitagawa) C. F. Fang; P. mandshuricum Skvortsov; P. yamatutae Kitagawa.
Herbs annual. Stems prostrate or ascending, 20-30 cm tall. Petiole very short, articulate at base; leaf blade elliptic or oblanceolate, 1-1.5 cm × 3-5 mm, abaxially with slightly prominent midvein and conspicuous lateral veins, adaxially with conspicuous midvein and inconspicuous lateral veins, base narrowly cuneate, apex slightly obtuse or acute; ocrea: lower part brownish, upper part white, membranous, 3- or 4-veined. Flowers 2-5, in axillary fascicles. Perianth green, margin white or pinkish, 5-parted to 2/3; tepals oblong, 1.5-2 mm. Achenes exceeding persistent perianth, dark brown, slightly shiny, narrowly ovoid, trigonous, 2-2.5 mm, densely minutely punctate, apex acute. Fl. Jun-Jul, fr. Aug-Sep.
Near fields, roadsides, in sand by riversides; sea level to 400 m. Heilongjiang, Jilin, Liaoning [Mongolia, Russia; North America].