Description from Flora of China
Annuals. Roots fibrous. Culms slender, 8-65 cm tall, compressed triquetrous, smooth, with few leaves at basal part. Leaves shorter than or equaling culm; sheath brownish, ± long; leaf blade 3-6 mm wide, flat, margin scabrous. Involucral bracts 3 or 4, leaflike, very much longer than inflorescence or basal 1 or 2 longer than inflorescence, margin scabrous. Inflorescence a simple or rarely compound anthela; rays 5-11, mostly to 15(-20) cm, unequal in length, each with 1(-5) spike. Spike ovate-oblong, broadly ovate, or oblong-cylindric, 1-3.5 × 1-3 cm, with 5-32 or many spikelets; rachis white hispidulous on angles. Spikelets slightly laxly or densely arranged, obliquely spreading to suberect, sometimes divergent after anthesis, narrowly ovoid to linear, 0.3-2.5 cm × 1-2 mm, 6-46-flowered; rachilla wings white, narrow, hyaline; successive glumes on rachilla ca. 1 mm apart. Glumes purplish red on both surfaces, slightly lax, broadly ovate to elliptic, 1.4-1.5 mm, membranous, obscurely 5-7-veined, keel abaxially green, margin apically white hyaline, apex rounded to retuse and muticous. Stamens 3; anthers ellipsoid, short; connective prolonged. Style short; stigmas 3, slightly short. Nutlet brown, obovoid, nearly as long as subtending glume, 3-sided, puncticulate, apex mucronate. Fl. and fr. Jul-Oct.
Mountain slopes, river margins, ditch margins, grasslands, along trails, wet places, paddy fields, swamps; 300-1500 m. Anhui, Chongqing, Fujian, NE Guizhou, Hebei, Heilongjiang, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Jilin, Liaoning, Nei Mongol, Shaanxi, Shandong, Zhejiang [Japan, Korea, Russia (Far East, E Siberia), Vietnam].