Dioecious, caespitose or rhizomatous perennial herbs; when caespitose mostly with short erect rhizomes largely covered by appressed scales; cluster and sand-binding roots mostly present. Cataphylls dark brown to black or the upper half paler. Culms all similar and unbranched or dimorpic with fertile culms branched and much shorter than sterile culms, terete or 4-angled and square in cross-section, straight or sinuose, glabrous or pubescent, smooth or rugose or striate, with few or numerous internodes. Sheaths mostly caducous and lax, with a slender lamina, the ligule a narrow flap or ridge of tissue, often pilose, adaxially at the base of the lamina. Male and female spikelets terminal or axillary in upper axils. Male spikelets many-flowered, with few or many sterile glumes at the base. Female spikelets 1–many-flowered; glumes with a rigid, black awn. Male flowers with 5 (6) tepals, 2 outer tepals keeled, inner tepals flat, stamens 3, anthers exserted. Female flowers with 1–5 tepals, ovary 1-locular with 1 style. Fruit a nut; shed with persistent perianth, stipe and stylar beak. Seed smooth with a pattern of irregular subangular cells. Culm anatomy: mostly with a central cavity; chlorenchyma continuous, mostly of a single layer of elongated peg cells; mostly with inward-projecting epidermal cells partially lining substomatal cavities; walls of epidermal cells thickened on outer wall and outer part of radial walls; radial walls often sinuous; often with radially elongated epidermal cells forming mounds on the culm surface; with stalked, branched multicellular hairs.
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