Japan Flora: culms rather soft, 30- 50 cm. long, typically 4-angled, or 3-, 5-, or 6-angled in forms (see below), sometimes rhizomatous; scales rather soft, elliptic or oblong, very obtuse, ferrugineous-sanguineous; bristles 6, as long as the style-base, with long, soft, plumose, whitish, spreading to slightly recurved hairs. July-Oct. Common in wet places in lowlands and mountains; Hokkaido, Honshu, Shikoku, Kyushu. Korea, Manchuria, and Ussuri.
f. petasata (Maxim.) Hara. Culms 3-angled.
f. teres Hara. Culms nearly terete or 5- or 6-angled.