A tufted leafless perennial with few to numerous crowded culms from a short rhizome, sometimes stoloniferous; roots numerous, light brown to reddish brown, sometimes spongy. Culms 30-120 cm long and 0.6-2.0 mm thick, rounded-angular, glabrous, the base covered with greyish black to purple leaf sheaths; as young the culm is erect but as mature it often curves outwards and eventually plants the inflorescence on the ground; each inflorescence gives rise to a new tussock. Leaf-blades absent, but the leaf-sheaths often end in a short triangular limb. Inflorescence a solitary reddish-brown head of 3-20 sessile spikelets, 1-4 cm in diameter, rarely with an additional stalked spikelet. Involucral bracts 1-2, culm-like, and usually shorter than the inflorescence. Spikelets 5-20 mm long and 2-6 mm wide, lanceolate, light to dark reddish brown, flattened, 15-40 flowered; the spikelets are produced continually and their size is therefore very variable within the same head. Glumes 4-5 mm long (but the lowest in each spikelet only 2-4 mm), ovate, boat-shaped, reddish brown with usually green 3-nerved very strongly scabrid keel; apex obtuse to acute. Stamens 3. Style long with 3 (rarely 2) long filiform branches. Nutlet 3.5-4.0 mm long and 1.0-1.2 mm wide, lanceolate in outline, somewhat flattened; apex long, acuminate; surface smooth; the darker seed surrounded by yellowish corky tissue, thus the nutlet long floating.
Marshes and dambos, on lake, stream and river margins and as part of floating aquatic vegetation mats; at elevations from 750-2,300 metres.
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