Description from Flora of China
Cyperus delavayi (C. B. Clarke) Kükenthal.
Perennials. Roots fibrous. Rhizomes short. Culms tufted, 40-60 cm tall, slender, acutely triquetrous, with a few leaves basally. Leaves shorter than culm; leaf blade 1-2 mm wide, usually folded. Involucral bracts 2, subulate, longer than inflorescence. Inflorescence a simple anthela; rays 2 or 3, mostly to only 2 cm, sometimes very short and inflorescence almost capitate, each with 2-10 spikelets. Spikelets laxly arranged, narrowly linear-ovoid to narrowly ovoid, 0.6-1.6 cm × 2.5-3 mm, obliquely spreading, 6-16-flowered; rachilla 4-angled, wingless, with successive glumes ca. 1.2 mm apart. Glumes blackish brown on both surfaces, slightly laxly imbricate, ovate, 2.7-3 mm, subleathery, veins 3 and straw-colored, apex acute. Stamens 3; anthers linear, 1-1.2 mm. Style slightly short; stigmas 2, slender. Nutlet black, oblong-obovoid, ca. 1.2 mm, ca. 1/2 as long as subtending glume, biconvex, densely prominently puncticulate, apex mucronate. Fl. and fr. Jun.
● Swamps, boggy seepages, shallow water; 2000-3000 m. Yunnan.