Herbs, perennial, dioecious, caespitose; the base with a woolly pubescence partly covered by glabrous cataphylls; cluster roots present. Cataphylls similar to sheaths but shorter. Culms unbranched or sometimes dimorphic with repeatedly branched sterile culms and taller less-branched fertile culms, erect, strongly compressed or ± terete, without scabrid edges, striate, glabrous or the lowest internode pubescent with branched multicellular hairs. Sheaths persistent, appressed, with a blunt or acute lamina; ligule a narrow ridge, pilose with dense long hairs. Male and female spikelets globose to ovoid, borne singly or in clusters, terminal or at a few upper nodes, on slender branches, erect or the males pendulous. Flowers: tepals 6, 2 outer tepals keeled, with a few hairs along keel; inner tepals slightly shorter, flat, glabrous. Male flowers: stamens 3, anthers not exserted. Female flowers: ovary 2-locular, style branches 2, mostly stigmatic. Fruit a capsule. Seeds with longitudinal lines of flat, rectangular or rhombic cells which are transverse or oblique to the long axis of the seed. Culm with chlorenchyma of 3 or 4 layers of short peg cells, interrupted opposite some outer vascular bundles by sclerenchyma girders extending from parenchyma sheath to epidermis; pillar and protective cells absent; central cavity present.
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