Scirpus komarovii Roshevitz in Komarov, Fl. URSS 3: 579. 1935; S. hondoensis Ohwi var. leiocarpus (Komarov) Ohwi; S. okuyamae Ohwi; S. sasakii Hayata var. leiocarpus (Komarov) Kitagawa; S. supinus Linnaeus var. leiocarpus Komarov.
Rhizomes very short. Culms tufted, 10-50 cm tall, terete, smooth, clothed at base with 2 or 3 bladeless leaf sheaths. Leaf sheaths green, 1-10 cm, base sometimes pale brown, mouth obliquely truncate. Involucral bract 1, culmlike, 8-18 cm, base slightly dilated. Inflorescence a pseudolateral head, with 2-10 or more spikelets. Spikelets sessile, ovoid to oblong-ovoid, 4-7(-10) × 2-3 mm, many flowered. Glumes pale brown with dark brown lines, oblong, ca. 2 mm, membranous, veins obscure, with green 1-veined costa excurrent into a mucro at rounded apex. Perianth bristles 4, ± as long as nutlet, retrorsely scabrous. Stamens 3; anthers narrowly ovoid, short; connective apex slightly evident beyond anthers. Style long; stigmas 2. Nutlet blackish brown, broadly obovoid, 1-1.5 mm, compressed biconvex, obscurely transversely wrinkled, shiny. Fl. and fr. Jun-Oct.
Swamps, wet places, paddy fields; near sea level to 100 m. Heilongjiang, Jilin, Liaoning, NE Nei Mongol [Japan, Korea, Russia (Far East)].