Japan Flora: Rhizomes loosely tufted and short-creeping，forming a large loose mat; culms 30-100 cm. long, scabrous on the angles above, rather soft; leaf-blades 3-5 mm. wide, soft, flat, the basal sheaths bladeless, reddish purple, reticulate-fibrous; staminate spikes 1 to 3, broadly linear, the pistillate 2 to 4, sometimes with a short staminate portion above, 2-5 cm. long, erect or nodding, sessile or peduncled, dark reddish purple, the lower 1 or 2 bracts leaf-like, nearly as long as the in­florescence; pistillate scales ovate, dark purplish crimson to dark blood-red, awnless or sometimes mucronate or awned (forma aristata Ohwi. Nagabo-tateyama-suge) ; perigynia about 3 mm. long, broadly ovate-oval, planoconvex, sometimes with 2 or 3 very slender nerves on each side, rather abruptly short-beaked, subentire; stigmas 2.  June-July. Wet sunny slopes in high mountains.

Honshu (centr. and n. distr. on the Japan Sea side); locally common.