大狗尾草 da gou wei cao

Setaria autumnalis Ohwi.

Annual. Culms solitary, erect or geniculate and rooting at the lowermost nodes, 50–120 cm tall, up to 6 mm in diam., glabrous. Leaves all cauline; leaf sheaths ciliate on upper margins; leaf blades broadly linear, 10–40 × 0.5–2 cm, glabrous or adaxial surface with scattered hairs, narrowed to base, apex acuminate; ligule 1–2 mm. Panicle densely cylindrical, 5–24 × 0.6–1.3 cm, nodding, branchlets bearing several spikelets each subtended by 1–3 bristles; axis white-pilose; bristles green or brownish purple, 10–15 mm. Spikelets elliptic, 2.8–3 mm, glumes and lower lemma thinly membranous; lower glume 1/3–1/2 as long as spikelet; upper glume 2/3–3/4 as long as spikelet; lower floret neuter; lower palea up to 1/2 as long as lemma, sometimes very small; upper lemma finely rugose under upper glume, almost smooth on exposed apex. Fl. and fr. Jul–Oct. 2n = 36.

Mountain slopes, roadsides, waste places. Anhui, Fujian, Guangxi, Guizhou, Heilongjiang, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Jilin, Shandong, Sichuan, Taiwan, Yunnan, Zhejiang [Japan, Korea; introduced in North America].

This robust, annual species is frequently confused with large forms of Setaria viridis, but has broader, acute spikelets and a shorter upper glume clearly exposing the tip of the upper lemma.