Herb, dioecious, rhizomatous, perennial, forming extensive patches. Rhizomes stout, densely covered with red-brown or yellow-brown hairs. Culms much-branched, upper branches often flexuose and sometimes forming dense trailing masses, terete, striate, glabrous, with persistent appressed sheaths. Male and female inflorescences similar, of spikelets terminal on culms or culm branches or sessile in the axil of an upper node; erect, elongated, cylindrical, many-flowered. Flowers with 6 tepals, 2 outer tepals keeled, the keel densely red-brown pubescent. Male flowers with 3 stamens, anthers exserted. Female flowers with a 2-locular ovary and 2 style branches strongly recurved and shortly connate at the base. Fruit a capsule. Seed surface smooth with longitudinal lines of transversely-elongated rectangular cells. Culm anatomy: chlorenchyma of 1 or 2 layers of somewhat elongated peg cells, interrupted by greatly enlarged epidermal cells that meet and interrupt the parenchyma sheath over girders opposite some outer vascular bundles (mostly over alternate bundles), pillar and protective cells absent, central cavity usually present.
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