Japan Flora: Rhizomes slender, terminated by a small tuber; culms 40-60 cm. long, 3-angled, about 2 mm. wide in upper part, without nodes, smooth, leafy at base; leaves slightly longer than the culm, flaccid, 3-angled, glabrous, 2-3 mm. wide, subobtuse; inflorescence corymbose, pseudolateral, 1-3 times dichotomously branched, with 5-8 loosely disposed spikelets; bract 1, continuous with the culm, erect, 10-20 cm. long; spikelets narrowly oblong to broadly lanceolate, 10-15 mm. long, 5-6 mm. thick, subacute, reddish brown; scales thin, narrowly oblong-ovate, 4-5 mm. long, obtuse, hyaline; stigmas 2; achenes obovate, biconvex, 2 mm. long, dark brown, dull; bristles 4, twice as long as the achene, retrorsely scabrous. July-Oct. Ponds and ditches.

Hok­kaido, Honshu, Shikoku, Kyushu; rare. Northeast China