Scirpus kamtschaticus C. A. Meyer, Mém. Acad. Imp. Sci. St.-Pétersbourg Divers Savans 1: 198. 1831; Eleocharis kamtschatica f. reducta Ohwi; E. komarovii G. Zinserling; E. mitrata Makino; E. sachalinensis (Meinshausen) Komarov; E. savatieri C. B. Clarke ex H. Léveillé; S. mitratus Franchet & Savatier (1878), not Grisebach (1864); S. sachalinensis Meinshausen.

Perennials. Rhizomes elongate. Culms 20-50 cm tall, 1.5-3 mm thick, terete, conspicuously obtusely ribbed and longitudinally sulcate, surface transversely septate when dry. Leaf sheaths 1 or 2, brownish, tubular, 6-7 cm or more, mouth slightly obliquely truncate, apex triangular mucronate. Spikelet ovoid to narrowly ovoid, 8-20 × 3-5 mm, many flowered, apex obtuse. Basalmost glume empty, amplexicaul for more than 1/2 of spikelet base; fertile glumes pale blood-red to straw-colored and ± with pale blood-red lines, tightly imbricate, oblong to ovate-oblong, ca. 4 × 1 mm, midvein obscure, margin broadly to narrowly hyaline, apex obtuse. Perianth bristles 4 or 5 but sometimes rudimentary or absent, slightly shorter than to as long as nutlet, densely retrorsely spinulose. Stigmas 2. Nutlet at first yellow then becoming tawny, obovoid, broadly obovate, or subglobose, 1-1.5 × ca. 1 mm, biconvex, smooth and shiny; persistent style base ovoid to mitriform, large, cellular spongy, 2/3 or more as long and nearly as wide as nutlet. Fl. and fr. Jul-Oct. 2n = 38-40, 44, 56.

River margins, marshes, wet places, especially in coastal habitats. Hebei, S Liaoning, Sichuan [Japan, Korea, Russia (Far East, E Siberia); North America].