Loosely tufted or forming loose masses in shallow water. Leaf-sheath closed, papery, light brown or purplish, glabrous, striate, keeled. Ligule (4)-8-10 mm, membranous, tapered. Leaf-blade 10-23 cm × (2)-4.5-7.5 mm, folded or flat, striate, minutely papillose to tubercular-scabrid especially on ribs; margins finely scabrid, rather abruptly narrowed to stiff tip. Culm (20)-45-75 cm, erect or spreading, sometimes prostrate or floating at base, few-noded, internodes glabrous. Panicle (20)-30-55 cm, secund, lax, linear, open at anthesis, later contracted; rachis smooth, branches sparingly scabrid, paired at lower panicle nodes, longer branch with 1-4 spikelets, shorter branch with 1-2 spikelets. Spikelets (15)-20-30 mm, 7-13-flowered, narrowly oblong, green or purple. Glumes unequal, elliptic-oblong; lower 2-3-(4) mm, 1-nerved, acute, upper 3-4-(5.5) mm, 1-(3)-nerved, subobtuse. Lemma 6-7.5 mm, 7-nerved, elliptic-oblong or oblong, subobtuse to subacute, minutely scabrid, margins later incurved; nerves not extending into wide hyaline upper margin. Palea = lemma, oblong-lanceolate, apex sharply, shortly bidentate, keel very minutely scabrid, scarcely winged. Rachilla 1.5-1.8 mm, glabrous. Anthers 1.5-2.5 mm. Caryopsis 2-3 × 0.7-1.2 mm.