Herb, dioecious, rhizomatous perennial, forming diffuse patches to 2 m across. Rhizome horizontal or ascending, 2–5 mm diam., often upwardly curving and continuous with an aerial culm; scales dark brown, covering a brown pubescence. Culms straight to sinuose or flexuose, terete or + compressed, striate, usually much-branched, 20–60 cm long, 1–2 mm diam., pubescent when young. Sheaths closely spaced at culm base, red-to grey-brown, partially pubescent when young, to 1.5 cm long, acute or sometimes aristate; lamina short, erect, to c. 3 mm long. Inflorescence: male spikelets singly or several on slender branches at uppermost nodes, pedicellate; pedicels and branchlets covered with a short whitish tomentum; female spikelets sessile, terminal and solitary, or pedicellate and 2–5 close together at uppermost nodes. Male spikelets cylindrical becoming narrow-elliptical to obovoid, 3–8 mm long; glumes 15–50, with 4–20 sterile lower glumes and 6–12 fertile upper glumes, ovate, acute to shortly mucronate, 2–3 mm long, concave, dark brown, with prominent midrib and hyaline membranous margin. Female spikelets erect, narrow-cylindrical or wider toward the apex, 6–15 mm long; glumes mostly 4–14, oblong-lanceolate, acutely-acuminate or occasionally shortly mucronate, 4–10 mm long, dark red-brown, glabrous. Male flowers: tepals 6, lanceolate, + acute; 2 outer tepals 1.5–1.8 mm long; inner tepals flat, 1.2–1.5 mm long; anthers 0.9–1.2 mm long. Female flowers: flower stalk with 1 or 2 bracts, one to 2–3 mm long, the second if present much smaller, c. 0.5–1 mm long; tepals to 1 mm long; style 3-branched. Fruit a nut with woody pericarp, ovoid, 2–4.5 mm long, c. 2 mm diam., shed with short stalk and perianth. Seed ovoid, orange-tan, c. 1.6 mm long, c. 0.9 mm wide. Culm anatomy: chlorenchyma of 2–4 layers of short cells, interrupted by pillar cells and partial sclerenchyma ridges opposite the outer vascular bundles.
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