Rhizome short. Culms tufted, 40-70 cm tall, compressed trigonous, scabrous above, leafy in middle or lower, clothed at base with black-brown bladeless sheaths disintegrating into fibers. Leaves shorter or longer than culm, blades pale green, 6-7 mm wide, flat, soft, margins serrulate, apex acuminate; membranous side of leaf sheath usually transversely wrinkled. Lower involucral bracts setaceous, upper ones glumelike. Inflorescence cylindric, sometimes slightly branching, 3.5-5 × 1-1.5 cm; spikes androgynous, slightly stellate patent, simple above, branched below. Female glumes pale green, ovate, 3-4 × ca. 1.8 mm, green 1-veined costa excurrent into an awn 0.5-1.2 mm. Utricles pale ferruginous, longer than glume, cuneate-lanceolate, plano-convex, 4-5 mm, membranous, lustrous, many veined abaxially, base spongy, shortly stipitate, upper margins narrowly serrate winged, apex gradually narrowed into a serrate-margined long beak, beak cleft abaxially, 2-toothed at orifice. Nutlets tightly enveloped, broadly ovate, plano-convex or slightly biconvex, 1.5-1.7 mm, base shortly stipitate; style base slightly thickened; stigmas 2. Fl. and fr. Jul. 2n = 48, 52.

Mixed forests, swampy meadows; 700-1700 m. Hubei, Jilin [Japan, Korea, Russia (Far East); North America].