Japan Flora: Larger; rhizomes long-creeping; culms stout, glabrous, 40-70 cm. long, somewhat thickened at base; leaf­blades flat, 5-10 mm. wide, the basal sheaths bladeless, partially dark reddish brown, sparsely fibrous; upper 3-5 spikes stami- nate, sessile, linear-cylindric, 2-4 cm. long, dark brown, ap­proximate, the lower 2-4 pistillate, cylindric, erect, 2.5-5 cm. long, short-peduncled, the bracts leaflike, the lowest sometimes sheathing; pistillate scales very obtuse, short-awned, castaneous to ferrugineous; perigynia longer than the scales, 6-7 mm. long, oblong, ligneous, faintly nerved, glabrous, gradually short-beaked, the tip bifurcate; stigmas 3, short. May-July. Wet places at mouth of rivers.

Hokkaido, Honshu, Kyushu; rare. Korea, Manchuria to Ussuri.