Perennial, with short rhizome and long stolons. Stems erect, tufted, slender, rigid, terete or obscurely angular, smooth, not transversely septate, 35-60 cm by (¾-)2-3(-5) mm. Sheaths membranous, closely appressed, purplish at the base, obliquely truncate, acute or rounded at the apex. Spikelet cylindrical, as broad as to distinctly broader than the stem, somewhat angular, acute, few-to several-flowered, pale green, (5-)10-20 by 3-4 mm. Glumes firm, loosely imbricate, appressed, oblong-ovate, obtuse, somewhat convolute when dry, many-nerved with prominent midnerve, usually brown-zonate within the broad scarious margins, 4-5 by 2-3½ mm. Bristles 5-7, coarse, up to 2-3 times as long as the nut, retrorsely scabrous in the upper half, yellowish or light brown. Stamens 2-3; anthers linear, 1-1½ mm, shortly apiculate. Style 2-3-fid. Nut turgidly and unequally biconvex, ribbed on the margins, obovate to broadly obovate, not constricted but with an annular prominence c. ½-¾ as wide as the nut at the apex, shining stramineous to greyish, 1½-2 by 1-1½ mm; epidermal cells small, transversely oblong, in 15-20 vertical series on either face, not pitted, the longitudinal ridges prominent. Style-base deltoid, flat, dark brown, ½-¾ mm high.
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Perennials. Stolons slender. Culms straw-colored, tufted, 37-75 cm tall, 2-3 mm thick, terete but sometimes apically obscurely 3-angled, without transverse septa, longitudinally canaliculate on surface when dry. Leaf sheaths 2 or 3, purplish red, tubular, 6-18 cm, mouth obliquely truncate, apex acute. Spikelet pale, cylindric, 2-4 cm × ca. 4 mm, few flowered, apex rounded to obtuse. Basalmost glume empty, broadly ovate, amplexicaul for whole spikelet base; fertile glumes straw-colored to pale brown, laxly imbricate, broadly oblong, ca. 5 × 3 mm, subleathery, purple puncticulate, many veined with an obscure midvein, margin hyaline, apex rounded to obtuse. Perianth bristles 6 or 7, ca. 2 × as long as nutlet, retrorsely spinulose. Stigmas (2 or)3. Nutlet pale yellow turning brown when mature, broadly obovoid, ca. 2 × 1.5 mm, compressed biconvex, longitudinally striate with 25-32 rows of transversely linear-oblong epidermal cells, apex not constricted but with an annular thickening; persistent style base narrowly long pyramidal, base ca. 1/2 as wide as nutlet. Fl. and fr. Sep-Oct.
In open wet places, swamps, on margins of lakes, floating islands etc., at low and medium altitudes (up to 1400 m), sometimes dominant.
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