Perennial with very short rhizome. Stems tall, tufted, trigonous but triquetrous at the top, smooth, 50-100(-200)cm by (3-)4-7(-10) mm. Leaves flat or often somewhat plicate with the midrib prominent beneath and 2 lateral nerves strongly marked above, scabrous on the margins, bright green above, pale green beneath, 4-10(-15)mm wide; lower sheaths purplish to almost black. Inflorescence compound or decompound, up to 30 cm across. Involucral bracts 4-8, much overtopping the inflorescence, up to 60(-75) cm long. Keel of the cladoprophylls scabrous, at least in the upper part. Primary rays up to 10, unequal, smooth, up to 20 cm long; secondary ones 2-5 cm. Spikes digitately arranged, narrowly cylindric, dense, 2-7 cm by 3-5 mm; rachis glabrous, narrowly winged. Spikelets spicately arranged, suberect, linear, compressed, 6-16-flowered, 3-6 by c. 1 mm; rachilla slightly flexuous, persistent; internodes ⅓-2/5 mm; wings caducous, yellow, c. ⅓ mm wide. Glumes membranous, appressed, ovate, acute, mucronulate, 1¼-1¾ by 1 mm, ½-⅔ imbricate; keel green or reddish brown, 3-5-nerved; sides golden to rufous. Stamens 3; anthers oblong-linear, c. ½ mm long; connective produced into an apical appendage c. ⅓ as long as the anther-cells and setulose at the top. Stigmas 3. Nut trigonous, ellip-soid, apiculate, yellowish to greyish brown, 0.8-0.9 by 0.3-0.4 mm.
Pond and stream margins; from near sea level to 1,500 metres. In swamps, wet rice-fields and meadows, on river-banks, and in other open wet places; at elevations up to 700 metres, very rarely to 1,000 metres.
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In swamps, wet rice-fields and meadows, on river-banks, and in other open wet places at low altitudes, 0-700 m, very rarely up to 1000 m.
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