虎尾草 hu wei cao

Chloris caudata Trinius ex Bunge.

Annual. Culms tufted, erect or geniculately ascending, slightly flattened, 15–100 cm tall. Basal leaf sheaths strongly keeled, glabrous; leaf blades flat or folded, 5–30 cm, 2–7 mm wide, glabrous, adaxial surface scabrous, apex acuminate; ligule 0.5–1 mm, glabrous or ciliate. Racemes digitate, 5–12, erect or slightly slanting, 2–10 cm, silky, pale brown or tinged pink or purple; rachis scabrous or hispid. Spikelets with 2 or 3 florets, 2-awned; lower glume 1.8–2.2 mm; upper glume 3–4 mm, acuminate; lemma of fertile floret obovate-lanceolate in side view, 2.8–3.5 mm, keel gibbous, conspicuously bearded on upper margins with a spreading tuft of 2.5–3.5 mm silky hairs, margins, keel and flanks silky-ciliate or glabrous; awn 5–15 mm; second floret sterile, oblong, glabrous, awn 4–10 mm; third floret occasionally present, reduced to a small clavate scale, awnless. Fl. and fr. Jun–Oct. 2n = 14, 20, 26, 30, 40.

Common on stony slopes, steppe, sandy riversides, roadsides, fields, plantations, frequent on walls and roofs; sea level to 3700 m. Gansu, Hebei, Heilongjiang, Henan, Jiangsu, Jilin, Liaoning, Nei Mongol, Ningxia, Qinghai, Shaanxi, Shandong, Shanxi, Sichuan, Xinjiang, Xizang, Yunnan [Afghanistan, Bhutan, India, Myanmar, Nepal, Pakistan; Africa, America, SW Asia, Australia, Pacific Islands].

This is a widespread and very variable, weedy annual, recognized by the conspicuous tufts of spreading, silky hairs on the upper lemma margins, together with a digitate inflorescence of erect racemes. It extends from the tropics well into temperate regions where the summers are hot.