Description from Flora of China
Scirpus densus Wallich in Roxburgh, Fl. Ind. 1: 231. 1820; Bulbostylis capillaris (Linnaeus) Kunth ex C. B. Clarke var. trifida (Kunth) C. B. Clarke; Isolepis densa (Wallich) Schultes; I. tenuissima D. Don; I. trifida Kunth.
Rhizomes absent. Culms tufted, 7-35 cm tall, slender, smooth. Leaf sheath pale, membranous, mouth long pilose; leaf blade filiform, 5-10(-13) × ca. 0.6 mm, papery, abaxially sparsely pilose, margin entire and slightly revolute, apex acuminate. Involucral bracts 2 or 3, setaceous to glumelike, 0.8-1.5 cm, much shorter than inflorescence, apex acuminate. Inflorescence a simple or subcompound anthela, with 4-7 spikelets; rays 3-5, 2-5 cm. Spikelets solitary or clustered, oblong-ovoid to ovoid, 3-6 × ca. 1.5 mm, 5-18-flowered, base rounded, apex acute. Glumes brown, ovate to broadly ovate, 1.5-2 × 1-1.5 mm, membranous, 1-3-veined, base rounded, margin ciliate, apex obtuse to rarely acute; empty glumes yellowish green, apex sometimes mucronate. Stamens 2; anthers oblong-ovoid to ovoid, base cuneate, apex acute. Style filiform; stigmas 3. Nutlet grayish purple at maturity, obovoid, ca. 0.8 × 0.5-0.6 mm, 3-sided, inconspicuously undulate-corrugate and puncticulate, apex contracted with a persistent depressed bulbous style base. Fl. and fr. Apr-Dec. 2n = 64.
Sandy wet places, waste slopes, trail margins, coniferous forests; 100-3200 m. Anhui, Chongqing, Fujian, Guangdong, Guangxi, Guizhou, Hebei, S Heilongjiang, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Liaoning, Shandong, Sichuan, Taiwan, E Xizang, Yunnan, Zhejiang [Bangladesh, Bhutan, India, Indonesia, Japan, Kashmir, Myanmar, Nepal, Papua New Guinea, Philippines, Russia (Far East), Sri Lanka, Thailand, Vietnam; tropical Africa, Australia, Pacific islands].