Herbs, perennial, dioecious, rhizomatous, forming large dense clumps or diffuse patches to 0.5 m across; cluster roots present. Rhizome 0.4–1 m long, 2–5 mm diam. Culms dimorphic or not dimorphic (when dimorphic the sterile culms shorter and finely branched), spaced to c. 2 cm apart, erect, terete to slightly compressed, 40–120 cm long, 0.6–2.0 mm diam. toward the base, glabrous to shortly villous, unbranched or branched, the branches slightly flexuose to sinuose; internodes 2.0–6.5 cm long. Sheaths 7–10 mm long, red-to dark-brown, glabrous to shortly villous, obtuse, not auriculate; lamina persistent, erect or reflexed, to 5 mm long. Male spikelets sessile, terminal and axillary on secondary branches, narrow-ovoid to cylindrical, 4–7 mm long, 1.5–2.0 mm wide; glumes 3–16, all fertile or the lowest glume sterile, broad-ovate, 2.0–3.2 mm long, dark brown, glabrous or sparsely hairy; mucro rigid, 0.2–1.1 mm long. Female spikelets mostly terminal on branches, 9–12 mm long, to c. 5 mm wide; 1–4 flowered; glumes 2–4, ovate, 4–7 mm long, rigid, striate, rarely pubescent, brown to dark brown with a narrow membranous margin; mucro erect, to 3 mm long. Male flowers: tepals 6, red-brown; outer tepals 2–3 mm long; filaments 2.0–2.5 (–3.5) mm long; anthers c. 1.0–1.5 mm long, exserted. Female flowers: tepals brown, rarely pubescent; outer tepals lanceolate, subulate, longer than inner tepals, 4.5–7.6 mm long; inner tepals broad, flat, acuminate, 2.7–6.0 mm long; ovary 2-locular, rarely only 1 loculus developing; style branches 2, shortly connate, recurved or recoiled. Capsule 4–9 mm long. Seed surface: cells slightly convex, lobed, separated from adjoining cells by deep narrow crypts. Culm anatomy: chlorenchyma of 2 or 3 layers of short peg cells, interrupted by sclerenchyma ridges opposite outer vascular bundles, central cavity usually present.
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