Description from Flora of China
Rhizome short, indurate. Plant wholly ferruginous puncticulate. Culms tufted, flattened, smooth, clothed with pinkish ferruginous bladeless sheaths at base. Leaves shorter or longer than culm, blades linear, 2-3 mm wide, flat, margins ± involute, scabrous, apex acuminate; membranous side of leaf sheath ferruginous. Lower involucral bracts leaflike, much surpassing inflorescence, sheathless, upper involucral bracts setaceous. Spicate inflorescence dense, pyramidal-cylindric, 2.5-8 × 1-1.8 mm; spikes numerous, androgynous, ovate, 5-8 mm. Female glumes ferruginous-yellow, ferruginous spotted, ovate to oblong-elliptic, 2-4 × ca. 1.5 mm, apex acute, shortly awned. Utricles ferruginous spotted, longer than glume, suberect, ovate or broadly ovate, plano-convex, 2.5-4 mm, membranous, many veined on both faces, densely ferruginous puncticulate above, margins from middle to apex with broad serrulate wings, apex gradually contracted into a beak, orifice 2-toothed. Nutlets pale brown, loosely enveloped, ovate or elliptic, plano-convex, ca. 1 mm, smooth, lustrous; stigmas 2. Fl. and fr. Jun-Aug. 2n = 108.
Wet places along ponds and riversides, grasslands; (below 100-)100-1700 m. Anhui, Gansu, Hebei, Heilongjiang, Henan, Jiangsu, Jilin, Liaoning, Nei Mongol, Shaanxi, Shandong, Shanxi [Japan, Korea, Russia (Far East)].