Description from Flora of China
Cyperus haspan var. flaccidissimus Kükenthal; C. haspan var. juncoides Kükenthal.
Perennials or annuals. Roots fibrous when annual. Rhizomes short to slightly long. Culms tufted or scattered, 10-60 cm tall, slender, compressed triquetrous, smooth. Leaves shorter than culm, sometimes sheathed only and bladeless; sheath pale green, base purplish brown to reddish purple, 2-10 cm; leaf blade 2-3 mm wide. Involucral bracts usually 2, leaflike, shorter to rarely longer than inflorescence. Inflorescence a simple, compound, or decompound anthela; rays 8-12, mostly 17-30 cm, unequal in length, each with several raylets; raylets less than 2 cm, usually with 1-6(-14) spikelets at apex. Spikelets digitately arranged or sometimes solitary, linear to narrowly linear-ovoid, 5-12 × 1-1.5 mm, 6-28-flowered; rachilla wingless. Glumes purplish brown, pale brown, or straw-colored but middle pale brownish to pale green, densely imbricate, oblong-ovate to subelliptic, ca. 1.5 mm, membranous, 3-veined, abaxially keeled, apex rounded to subtruncate and mucronate. Stamens 1-3; anthers narrowly oblong, apex white setose. Style of medium length; stigmas 3. Nutlet yellowish, whitish, or reddish brown, broadly obovoid, 0.5-0.6(-0.7) mm, ca. 1/3 as long as subtending glume, 3-sided, tuberculate. Fl. and fr. over a long period, different in each region. 2n = 26.
Sparse forests, grasslands on mountain slopes, sand by river margins, swamps, ditch margins in valleys, wastelands, wet places, along trails, dry fields, paddy fields; near sea level to 1600 m. Anhui, Fujian, Guangdong, Guangxi, Hainan, S Henan, Hubei, Hunan, S Jiangsu, Jiangxi, Taiwan, SE Xizang, S Yunnan, Zhejiang [Bhutan, Cambodia, India, Indonesia, Japan, Kashmir, Korea, Laos, Malaysia, Myanmar, Nepal, Pakistan, Papua New Guinea, Philippines, Sri Lanka, Thailand, Vietnam; Africa, tropical America, SW Asia, Australia, Indian Ocean islands, Madagascar, North America, Pacific islands].