Rhizomes stout, creep­ing, short; culms thick, terete, glaucous-green, 1-2 m. long; basal sheaths cylindric, with a short subulate blade to 10 cm. long; inflorescence pseudolateral, umbelliform, once to twice compound, with 4-7 rays; bract 1, continuous with the culm; spikelets in groups of 2 or 3 or solitary, ovoid, reddish brown, 5-10 mm. long; scales membranous, elliptic to broadly ovate, about 3 mm. long, ciliate, with reddish brown flecks, shallowly bifid and mucronate; stigmas usually 2, rarely 3; achenes 2 mm. long, biconvex, dark grayish brown, smooth; bristles as long as the achene, retrorsely scabrous. July-Oct. Ponds and lake margins.

Hokkaido, Honshu, Shikoku, Kyushu;  common. Sakhalin, Kuriles, Korea to Europe. Very vari­able. 

f. creber. Spikele usually aggregated, dark colored. Occurring chiefly in northern areas.
f. luxurians Miq. Spikelets numerous, usually solitary, light colored, scarcely flecked. Common in central areas.
f. australis Ohwi. Spikelets densely disposed, 10-15 mm. long, light colored, not flecked. Common in southern areas.     
cv. Zebrinus. Culms transversely white-banded. Cultivated.
cv. Pictus. Culms longitudinally white-lined. Cultivated.