Description from Flora of China
Rhizomes yellow, 2-7 cm × 2.5-3.5 mm, shiny, with black scales. Culms scattered, 5-60 cm tall, 0.7-4 mm thick, compressed 3-angled, clothed at base with brown to purplish brown leaf sheaths. Cauline leaves shorter than culm; ligule pale, very short; leaf blade flat, 0.5-4 mm wide, membranous, involute, margin scabrous, apex acuminate. Involucral bract leaflike, usually surpassing inflorescence; bractlets glumelike, membranous. Inflorescences consisting of 3-10 or more spikelets, densely arranged in a distichous or subdistichous spike; basal 1 or several spikelets usually remote, 1.5-3 × 0.6-1.1 cm. Spikelets narrowly ovoid, ovoid, or long ellipsoid, 5-7 mm, 2-9-flowered. Glumes rust-colored brown, subdistichous, long ovate, 3.5-4.5 mm, 3-5-veined, keel green, apex acute. Perianth bristles 3-6, flexuose or contorted, 2-3 × as long as nutlet, retrorsely scabrous. Stamens 3; anthers narrowly oblong, 2-2.5 mm; connective apex ca. 0.3 mm. Stigmas 2, ± as long as style. Nutlet dark brown, broadly obovoid, ca. 2 mm, plano-convex. Fl. and fr. Jun-Sep.
Wet places, stream and river margins, riverbeds, grasslands, valleys, swampy meadows, slopes; 500-4800 m. Gansu, Hebei, Liaoning, Nei Mongol, Ningxia, Qinghai, Shaanxi, Shanxi, Sichuan, Xinjiang, Xizang, NW Yunnan [Mongolia].