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)].