Perennial with creeping or floating spongy rhizomes; culms 30-200 cm high, prostrate and rooting at the nodes below. Leaf-blades 5-25 cm long, 3-8 mm wide, flat or folded, bluntly acute to acuminate. Inflorescence 10-30 cm long; racemes 1-6 cm long, their rhachis narrowly winged, 0.5-1.5 mm wide. Spikelets ovate-elliptic, 2-3 mm long; lower glume truncate, a quarter the length of the spikelet; upper glume one-eighth to three-quarters the length of the spikelet; lower floret sterile, without a palea, its lemma four-fifths to as long as the spikelet, often with the nerves slightly raised; upper lemma rugulose.