Description from Flora of China
Cyperus rotundus var. quimoyensis L. K. Dai.
Perennials. Stolons slender, with ellipsoidal tubers. Culms solitary, rarely 2 laxly tufted, 15-90 cm tall, slightly slender, triquetrous, smooth, base swollen into a tuber, leaved at basal part. Leaves equaling or shorter than culm; sheath brown, usually disintegrating into fibers; leaf blade bluish green, 2-5 mm wide, ± flat. Involucral bracts 2 or 3(-5), longer to sometimes shorter than inflorescence. Inflorescence a simple or compound anthela; rays (2 or)3-10, mostly to 12 cm, unequal in length, spreading. Spikes obdeltoid, with 3-10 slightly laxly arranged spikelets. Spikelets obliquely spreading, linear, 1-3 cm × 1.5-2 mm, 8-28-flowered; rachilla wings white, slightly broad, hyaline. Glumes blood-red to purplish brown on both surfaces but middle green, subdensely imbricate, ovate to oblong-ovate, ca. 3 mm, 5-7-veined (fading some distance before margin), apex acute to obtuse and muticous. Stamens 3; anthers linear; connective prominent beyond anthers. Style long; stigmas 3, longer than style, exserted from glume. Nutlet obovoid-oblong, 1/3-2/5 as long as subtending glume, 3-sided, puncticulate. Fl. and fr. May-Nov. 2n = 80, 84, 96, 100, 104, 108, 110, 112, 116, 124, 132, 138, 160, ca. 200.
The tubers are used as a Chinese medicine. The species is generally considered to be one of the world’s worst weeds.
Grasslands, wet or dry areas on mountain slopes, stream margins, along trails, sandbanks, ditch margins, water margins in valleys, paddy field margins; near sea level to 2100 m. Anhui, Chongqing, Dongsha Qundao, Fujian, S Gansu, Guangdong, Guangxi, Guizhou, Hainan, Hebei, Henan, Hubei, Hunan, Jiangsu, Jiangxi, S Liaoning, Nansha Qundao, S Shaanxi, Shandong, Shanxi, Sichuan, Taiwan, Xisha Qundao, SE Xizang, Yunnan, Zhejiang [Afghanistan, Bhutan, India, Indonesia, Japan, Kazakhstan, Korea, Kyrgyzstan, Malaysia, Myanmar, Nepal, Pakistan, Papua New Guinea, Philippines, Sri Lanka, Tajikistan, Thailand, Uzbekistan, Vietnam; Africa, SW Asia, Australia, Central, North, and South America, Europe, Indian Ocean islands, Madagascar, Pacific islands].