Description from Flora of China
Rhizome slender, stoloniferous. Culms densely tufted, 10-35 cm tall or more, slender, triquetrous, smooth, scabrid near apex. Leaves basal, shorter than or equaling culm, blades 2-3 mm wide, flat or sometimes slightly conduplicate, scabrous on margins, sheathed; sheaths 2-3 cm, usually splitting. Involucral bracts sheathed, lower blades linear, upper blades setaceous; sheaths 5-10 mm, lateral part of sheath membranous, brown. Spikes 3 or 4(-8), single in an involucral bract sheath, space up to 5.5 cm, uppermost 2 ± contiguous, androgynous, terminal spike with male part longer than female part, lateral spikes with female part longer than male part, oblong, 8-15 mm, female part slightly densely few to more than 10-flowered; peduncles thin. Female glumes reddish brown, ovate, 2-2.5 mm, membranous, 3-veined, apex acute, muticous. Utricles reddish brown, suberect, longer than glume, broadly elliptic or broadly ovate, plano-convex, ca. 3 mm, membranous, thinly several veined abaxially, base abruptly contracted into a short stipe, apex abruptly narrowed to a short beak, beak less than 1 mm, hispidulous on margins, orifice shortly 2-toothed. Nutlets yellowish, tightly enveloped, suborbicular, compressed plano-convex, ca. 2 mm, base estipitate; style base slightly thickened; stigmas 2, exserted part longer than utricle. Fl. and fr. Aug-Oct.
Thickets, grasslands, wet places on mountain slopes, ditch sides in valleys, rock crevices, field banks; 100-1900 m. Guizhou, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Shaanxi, Sichuan, Zhejiang [Japan].