鼠尾粟 shu wei su

Agrostis fertilis Steudel, Syn. Pl. Glumac. 1: 170. 1854; Sporobolus elongatus R. Brown var. purpureosuffusus Ohwi; S. fertilis (Steudel) Clayton var. purpureosuffusus (Ohwi) P. C. Keng & X. S. Shen; S. indicus (Linnaeus) R. Brown subsp. purpureosuffusus (Ohwi) T. Koyama; S. indicus var. major (Buse) Baaijens; S. indicus var. purpureosuffusus (Ohwi) T. Koyama.

Perennial. Culms densely tufted, erect, rigid, 25–100(–120) cm tall. Leaf sheaths glabrous but margin ciliolate, basal sheaths papery, lightly keeled; leaf blades linear, flat or involute, 15–50(–65) × 0.2–0.5 cm, glabrous or adaxial surface thinly pilose, tapering to a long filiform apex; ligule ca. 0.5 mm. Panicle linear, contracted to spikelike, often interrupted especially at base, 7–45 × 0.5–1.5 cm; branches 1–2.5(–5) cm, erect and appressed to main axis, or looser and narrowly ascending, densely spiculate throughout. Spikelets grayish or yellowish green, 1.7–2 mm; lower glume oblong, ca. 0.5 mm, veinless, apex truncate-erose; upper glume oblong-elliptic, 1/2–2/3 spikelet length, 1-veined, ± acute; lemma ovate, as long as spikelet, indistinctly 1(–3)-veined, acute. Anthers 3, 0.8–1 mm. Grain red-brown, obovate-elliptic, 0.9–1.2 mm, distinctly shorter than its lemma and palea, these gaping widely beyond its top, apex truncate. Fl. and fr. Mar–Dec. 2n = 36, 48, 54.

Roadsides, field margins, grassy places on hill slopes, moist ground of mountain valleys. Anhui, Fujian, Gansu, Guangdong, Guizhou, Hainan, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Shaanxi, Shandong, Sichuan, Taiwan, Xizang, Yunnan, Zhejiang [Bhutan, India, Indonesia, Japan, Malaysia, Myanmar, Nepal, Philippines, Sri Lanka, Thailand, Vietnam; occasionally introduced elsewhere].

This common and variable, perennial weed is distinguished by its contracted panicle and short glumes. The spikelets are frequently infected by a black smut fungus.