Herbs, perennial, dioecious, rhizomatous; cluster roots present. Rhizomes densely pubescent with white or pale brown hairs; scales pale, glabrous or pubescent. Culms terete or compressed or grooved, striate, pubescent or glabrous, with appressed persistent sheaths, sometimes dimorphic with fertile culms taller than much-branched and strongly flexuose vegetative culms; sheaths with a short narrow lamina, the ligule a narrow membranous ridge¸ glabrous or with sparse or dense hairs. Inflorescences of several or many spikelets terminal and axillary at upper nodes. Male spikelets many-flowered; glumes acuminate or awned. Female spikelets mostly terminal on culms or culm branches, 1–5-flowered; glumes rigid and with a black awn or mucro. Male flowers with 4 or 6 membranous tepals; outer tepals keeled; inner tepals shorter, flat; stamens 3, anthers exserted. Female flowers with 4–6 tepals, outer tepals rigid, keeled; ovary of 2 carpels but often only 1 developing, 1-or 2-locular; style 1-or 2-branched, persisting as a rigid beak on the fruit, when branched shortly connate at base or the lower ⅓–½ connate, the branches recoiled or recurved, plumose. Fruit a smooth brown woody capsule, broadest near apex, dorsiventrally compressed, heart-shaped if 2 carpels develop, obconical if only 1 carpel develops. Seed obloid, with a longitudinal abaxial furrow; seed surface of slightly convex, lobed, cells, separated from the adjoining cells by deep narrow crypts. Culm anatomy: chlorenchyma of 2 or 3 layers of short peg-cells, interrupted by pillar cells and/or sclerenchyma ridges opposite the outer vascular bundles, protective cells absent, central cavity usually present.
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