Herb, dioecious, rhizomatous perennial. Rhizomes 2–7 mm diam., glabrous, covered with closely imbricate, pale brown, glossy, scarious scales. Culms ascending at base, crowded or spaced to c. 2 cm, mostly unbranched below the inflorescence, 60–130 cm long, terete, 0.8–2 (–2.5) mm diam. Sheaths 0.5–1.0 (–1.7) cm long, striate, brown, glabrous, truncate to acuminate; margin hyaline, 3–8 mm wide. Male spikelets mostly small, numerous, on slender drooping branches, oblong-ovoid, 2–5 mm long, c. 1 mm diam., with 1–4 sterile lower glumes and 5–8 fertile upper glumes; glumes imbricate, ovate, obtusely to acutely acuminate, 1.8–2.7 mm long (often with a short mucro c. 0.3 mm long), brown, not glossy, with narrow indistinct pale hyaline margin, glabrous. Female spikelets solitary, erect and terminal or 2–10 (–25) shortly pedicellate erect spikelets in a narrow fascicle, oblong-cylindrical becoming turbinate, 5–25 mm long, with up to 4–6 sterile lower glumes and 8–20 fertile upper glumes; glumes broad-ovate, acuminate, 6–9 mm long, red to dark-brown, coriaceous, mostly glabrous, abaxially partially pilose, with a tapering awn that becomes somewhat reflexed; bracts on the floral axis absent. Male flowers: tepals (5 or) 6, ovate, obtuse to acuminate, thin, membranous, pale, brown-hyaline, glabrous; 2 outer tepals keeled, 0.8–1.6 mm long; inner tepals flat, slightly shorter; stamens 3, filaments very short, to 0.3 mm long, anthers 0.8–1.2 mm long. Female flowers: base with tuft of pale hairs; tepals 6, pale; 2 outer tepals rigid, acute, cymbiform, thick and spongy near the keel, 2.5–4.0 mm long, the margins often with very short rigid hairs; 2 inner tepals thin, narrow-lanceolate, keeled, acute, 1.5–3.5 mm long, very shortly ciliate; 2 innermost tepals narrow-lanceolate, acute, 1–2.5 mm long, shortly ciliate; style 3-branched, the lower half fused, the upper half stigmatic. Nut narrow-ovoid, 1–3 mm long; pericarp hyaline. Culm anatomy: chlorenchyma interrupted by groups of pillar cells that extend from the parenchyma sheath to the epidermis.
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