Plant with spreading spongy rhizomes. Culms robust, erect from a decumbent base, rooting at lower nodes, 0.7–2 m tall. Leaf sheaths smooth, glabrous; leaf blades 15–40 cm × 4–10 mm, smooth, margins sharply scabrid, apex finely acuminate; ligule 3–8 mm, truncate. Panicle loose, elliptic to ovate in outline, 15–30 cm; branches 2–4 at each node, erect at first, spreading after anthesis, naked in lower half, scabrid. Spikelets 7–10 mm, florets (2–)3–4(–5); glumes broadly lanceolate, lower glume 6.5–8 mm, upper glume 7.3–10 mm; lemmas 6–8 mm; palea lanceolate, ca. 6 mm. Anthers 2.5–3.4 mm. Fl. Jun–Aug. 2n = 28.
"Stout, erect, 10–18 dm; lvs 5–10 mm wide, elongate to a slender tip; ligule firm, 3–5 mm; panicle 1–2 dm, the branches ascending, bearing spikelets mostly above the middle, the lowest ones much elongate; spikelets 7–11 mm; glumes lanceolate, appressed, the first 5–7.5 mm, the second 6.5–10 mm; lemmas usually lacerate at the tip and with minutely projecting veins, the lowest 6–7 mm, the upper considerably smaller; 2n=28. Marshes and shallow water; n. Eurasia and nw. N. Amer., s. and e. to Oreg., Mont., Kans., and Io. (Fluminia f.)"