Plants perennial; rhizomatous, sometimes producing aquatic leaves when submerged. Culms (5)10-100 cm, erect, glabrous, rooting at the lower nodes; nodes glabrous. Sheaths of aquatic leaves closed to near the apices, translucent, pale pinkish-brown; collars inconspicuous; ligules acute; blades pinkish-brown. Sheaths of aerial leaves usually closed for over 1/2 of their length, sometimes open to the base, opaque, green to olive-green, glabrous; collars conspicuous as a zone of contrasting color; auricles absent; ligules membranous, truncate, lacerate; blades usually flat, glabrous, upper blades conspicuously longer than the lower blades. Inflorescences open panicles; branches stiff and ascending to pendulous, glabrous. Spikelets pedicellate, somewhat laterally compressed; florets (1)2-7(9); rachillas prolonged beyond the uppermost floret, glabrous; disarticulation above the glumes. Glumes subequal, broadly lanceolate to ovate, membranous to subcoriaceous, glabrous, 1-3(-5)-veined, acute to obtuse; calluses short, blunt, bearded to almost glabrous; lemmas ovate, glabrous, membranous to subcoriaceous, with 3(5) obscure veins, apices entire, obtuse; paleas subequal to the lemmas; lodicules 2, free, glabrous, toothed or entire; anthers 3; ovaries glabrous. Caryopses falling free; hila broadly ovate, 1/6-1/5 the length of the caryopses. x = 7. From the Greek arktos, north, and philia, loving.