Cyperus sanguinolentus Vahl, Enum. 2: 351, 1805, nom. illeg. C. albidus Lamarck, Tabl. Encycl.: 146. March 1791, non Retz. Jul.-Nov. 1791; C. erythraeus Schrad., in Schult., Mantissa 2: 477. 1824; T. Koyama, in Fl. Taiwan 5: Pl. 1343. 1979.

Small annual or perennial, 10-30 cm; plants single or in small tufts. Roots fibrous; stem base in older plants decumbent and rooting. Stem 0.5-1.5 mm diam., trigonous, smooth. Leaves shorter than stem; sheaths up to c. 50 mm, soft, grey brown, sometimes slightly reddish, mouth margin almost straight; blades up to 12 cm, 1-3 mm wide, green, flat or folded, keeled, straight or falcate, margins narrowly recurved, smooth, apex obtuse, flat or trigonous, smooth. Inflorescence one single digitate, rather loose cluster of 3-12 spikes, or with 1-2 primary branches up to 15 mm; bracts 1-3 foliose, up to 10 cm, spreading, with spongy, undifferentiated tissue in their axils; spikes 5-15 x 2.5-3 mm, with 8-18 glumes, somewhat turgid; glume-like bracts c. 2.2 mm, glume-like prophyll c. 1.6 mm; rachis c. 0.5 mm diam., almost quadrangular, internodes 1.1-1.5 mm, with scarious, triangular appendage present on both sides; glumes 1.5-2 mm, cymbiform, mucronate, mid-nerve area green or later yellow brown, on both sides wide reddish marginal zone, sides nerve-less or with 1-2 inconspicuous nerves. Stamens 3. Nut 1.3-1.6 x 0.9-1 mm, lenticular, ellipsoid or obovoid, brown or dark brown, finely reticulate and often papillose, glossy.

Fl. Per.: July - September.

Neotype: NW Himalaya, Distr. Tehri-Garhwál, 3000 ft., Oct. 1894, J.S. Gamble 15117 (L-951.65-240) selected by Kern in Reinwardtia 3: 54, 1954.

Swamps, wet meadows, also rice fields; from 650 to 2600 m; Distribution: From NE Turkey and Caucasus to Japan and Malesia; NW India, Pakistan, Tadjikistan, N to Kazakhstan, China.

Kern (1954) distinguishes several subspecies within P. sanguinolentus. Plants from Caucasus and Tadjikistan are frequently assigned, e.g. by Egorova, in Consp. Fl. Asiae Mediae 5(1976) and Ikonnikov, Definit. Pl. Vasc. Badachschaniae (1979) to P. korshinskyi (Meinsh.) V. Krecz., treated by Kükenthal (1936) as C. sanguinolentus var. korshinkyi (Meinsh.) Kük. Egorova (Novit. Syst. Pl. Vasc. 28, 1991) includes P. korshinskyi in P. sanguinolentus.