Rhizome long stoloniferous. Culms 20-45 cm, triquetrous, rather slender, scabrid at upper part, red-brown sheathed at base, sheaths sometimes disintegrating into fibers. Leaves shorter than culm, blades 1.5-2.5 mm wide, slightly plicate, grooved at middle, scabrous on margins, sheathed. Involucral bracts leaflike, with short involucral bract leaf, involucral bract sheaths short. Spikes 2 or 3, remote; terminal spikes male, erect, linear, 2-2.5 cm, pedunculate; lateral spikes female, sometimes with few male flowers at apex, oblong or ovate, 1-2 cm, subdensely many flowered, peduncles slender, often pendent. Female glumes yellowish brown, ovate or lanceolate-ovate, 4-6 mm, green at middle, 1-3-veined, apex hard mucronate. Utricles suberect, slightly shorter than glume, ovate or elliptic, compressed trigonous, 3.5-4 mm, leathery, glabrous, densely punctate, several veined, base rounded, shortly stipitate, apex abruptly narrowed into a very short beak, orifice truncate or emarginate. Nutlets slightly loosely enveloped in utricles, elliptic, compressed trigonous, ca. 2 mm; style exserted from utricle, persistent, base not thickened; stigmas 3. Fl. and fr. May-Jul.

Swamps, grasslands at watersides. Heilongjiang, Liaoning [Japan, Korea, Mongolia, Russia (Far East, Siberia); Europe, North America].