8. Polygonum arenastrum Boreau, Fl. Centr. France, ed. 3. 2: 559. 1857.
伏地萹蓄 fu di bian xu
Polygonum planum Skvortsov; P. polyneuron Franchet & Savatier; P. prostratum Skvortsov (1943), not R. Brown (1810), nor Roxburgh ex D. Don (1825).
Herbs annual. Stems procumbent or ascending, 15-30 cm tall, branched from base. Petiole short, articulate at base; leaf blade elliptic or oblanceolate, 0.5-2 cm × 2-5 mm, both surfaces with conspicuous veins, base narrowly cuneate, margin entire, apex usually obtuse; ocrea white, 2-3 mm, membranous, 5-7-veined, lacerate. Flowers 3-5, in axillary fascicles; bracts narrowly ovate, apex acute. Pedicel articulate at apex. Perianth green, 5-cleft to 1/2, veined, margin white; tepals oblong. Stamens 8; filaments dilated at base. Styles 3, very short; stigmas capitate. Achenes included in persistent perianth, dark brown, opaque, narrowly ovoid, trigonous, rarely biconvex, 2-2.5 mm, densely minutely granular striate. Fl. Jun-Aug, fr. Jul-Sep. 2n = 40, 60.
In sand at riversides, grasslands; 100-300 m. Heilongjiang [Japan, Korea, Mongolia, Russia; Europe, North America; widely introduced elsewhere including Australia].