Japan Flora: Rhizomes short; sterile culms elongate, with nodes and many leaves; fertile culms tufted, 40-60 cm. long, acutely angled, scabrous; leaf-blades 2-3 mm. wide, soft, flat; head cylindric, 3-5 cm. long, the bract usually small, scale- like; spikes several to numerous, approximate, gynecandrous, ovoid-globose, 5-8 mm. long, light green, densely flowered; pistillate scales pale, ovate, obtuse, the midrib broad, green; perigynia twice as long as the scales, ovate, 3.5 mm. long, slightly recurved at tip, concavo-convex, inconspicuously nerved, prominently spongy toward the periphery, margins scabrous near tip and narrowly winged, the beak distinct, minutely 2-toothed at tip; stigmas 2.  May-June. Wet grassy places along rivers in lowlands.

Hokkaido, Honshu, Kyushu; locally common. Amur, Ussuri, Korea, and China.