Summer-green perennial. Rhyzome 2–8 mm. diam., woody, with thin, grey, papery scales at the nodes and reddish fibrous roots. Culms (15)–30–60–(120) cm. × 1–4 mm., triquetrous, with concave sides, smooth, soft, pale sea-green; 1–2 thin, membr. sheaths at base. Lvs 1–4, < stem, 1–3 mm. wide, linear, channelled, becoming triangular with margins sparingly scabrid towards the obtuse tip, adaxial surface membr. with internal septa clearly visible; sheaths long, closed, largely membr. Infl. apparently lateral, of 1–4 unequal, closely compacted, sessile spikelets; subtending bract 2–6 cm. long, similar to stem and continuous with it, scabrid towards the tip. Spikelets 6–11×3–5 mm., ovate, elliptic, dark purple-brown. Glumes broadly ovate, smooth, membr., margins fimbriate, emarginate, midrib produced to a mucro <, = or rarely slightly > small, round teeth of glume apex. Hypog. bristles 2–6, < nut, retrorsely scabrid, red-brown. Stamens 3. Style-branches 3. Nut c. 3×2 mm., obovoid, plano-convex to subtrigonous, prominently apiculate, smooth, grey-brown.