Description from Flora of China
Rhizome short. Culms tufted, 30-70 cm tall, stout, triquetrous, scabrous on upper part, few purple-brown and bladeless sheathed at base, rudimentary sheaths sometimes disintegrating into fibers. Leaves longer than or slightly shorter than culm, blades 3-8 mm wide, flat, slightly stiff, with 2 distinct lateral veins and with short and transverse septate nodes, sheathed. Involucral bracts leaflike, longer than spike, usually not sheathed. Spikes 3-5, congregated at top of culm, sometimes lowermost one slightly remote; terminal spike male, usually not surpassing or slightly longer than contiguous female spike, clavate or linear-cylindric, 2-3 cm, subsessile; lateral spikes female, oblong-ovate or shortly cylindric, 2-3 × 1.5-2 cm, densely many flowered, very shortly pedunculate or subsessile. Female glumes brownish laterally, oblong, 4-5 mm, thickly membranous, greenish 3-veined in middle abaxially, apex acuminate and aristate, awn nearly as long as glume, scabrous on margins. Utricles yellowish green, obliquely patent or divaricate, longer than glume, narrowly lanceolate, compressed trigonous, 6-8 mm, thickly membranous, smooth, glabrous, several veined, base abruptly contracted into a short stipe, apex gradually narrowed to a long beak, orifice long 2-toothed, teeth ca. 2 mm, recurved toward both sides. Nutlets dark brown, loosely enveloped, elliptic, trigonous, 1-1.5 mm; style slender, tortuous, base not thickened; stigmas 3, rather short. Fl. and fr. May-Aug.
Riversides, lakesides, swamps or wet places. Heilongjiang, Jiangsu, Jilin, Liaoning [Japan, Korea, Russia (Far East)].