Plants annual; aquatic, floating or rhizomatous. Culms 4-55 cm, erect; nodes pubescent. Sheaths glabrous or pubescent; ligules 1-4 mm; blades 10-40 cm long, 8-22 mm wide, flat, glabrous or sparsely pubescent. Panicles terminal, with (7)20-70 racemosely arranged branches; branches 1.2-9.5 cm, diverging to spreading, occasion¬ally arcuate, disarticulating at maturity; branch axes 0.7-1.5 mm wide, broadly winged, glabrous, margins scabrous, extending beyond the distal spikelet. Spikelets 1.1-1.9 mm long, 0.5-0.8 mm wide, solitary, appressed to the branch axes, elliptic, pubescent, white. Lower glumes absent; upper glumes and lower lemmas veinless; upper florets white. Caryopses 0.8-0.9 mm, translucent, white. 2n = 20.