Perennial, rhizomatous; rhizome stout, creeping. Culms erect, succulent, 20–70 cm tall, unbranched. Leaf sheaths closed up to middle, upper shorter than internodes; leaf blades equally wide throughout, soft, 5–20 cm × 2–8 mm, apex boat-shaped; ligule 2–5 mm, obtuse. Panicle open or loosely contracted at anthesis, ovate to oblong in outline, 10–30 × 4–12 cm; branches whorled, slender, usually obliquely ascending, up to 10 cm, often bare of spikelets in lower part. Spikelets with (1–)2(–3) florets, 2–4(–5.8) mm; glumes obtuse or subtruncate; lower glume ovate to suborbicular, 0.5–1.2(–2) mm; upper glume broadly elliptic, 1–2(–3) mm; lemma 1.5–3 mm, green becoming brown at maturity, usually glabrous, apex truncate. Anthers 1–2 mm. Fl. and fr. Apr–Aug. 2n = 20.
"Culms 1–7 dm; lvs 3–8(–10) mm wide; infl 8–15 cm, the finely hairy branches divergent, in fascicles of ca 5; first glume ovate, 1–1.7 mm; second glume oblong, truncate and usually erose, 1.6–2 mm; lemmas broadly oblong, 2.2–3 mm, glabrous; anthers 1–1.3 mm; 2n=20. Shallow water or wet soil; circumboreal, s. to N.B., Wis., Nebr., and Ariz."