Perennial from a knotty rootstock. Culms loosely tufted, erect or decumbent, 45–130 cm tall, up to 6 mm in diam. Leaf sheaths ± papillose-pilose, margins usually ciliate; leaf blades narrowly lanceolate, plicate, thin, 10–40 × 1–3 cm, papillose-pilose, hispidulous or glabrous, narrowed toward base, apex attenuate; ligule ca. 3 mm, ciliate. Panicle 15–33 cm, branches up to 8 cm, loose, ascending, some spikelets subtended by a single 10–20 mm bristle. Spikelets ovate-oblong, 3–4 mm, acute; glumes with broad papery margins; lower glume ovate-orbicular, 1/4–1/3 as long as spikelet, obtuse to truncate; upper glume 1/2–3/4 as long as spikelet, 5–7-veined, obtuse or acute; lower lemma staminate or neuter, usually equaling upper floret, 5-veined; lower palea often well developed; upper lemma usually distinctly rugose, rarely smooth, apiculate. Fl. and fr. Jun–Oct. 2n = 36.

Setaria plicata is a more slender species than S. palmifolia, with a narrower panicle of shorter branches. However, the two species intergrade and must be separated by a combination of characters, as none is reliable on its own. Besides the key characters, S. plicata usually has a more distinctly rugose upper floret and shows a greater tendency to develop anthers in the lower floret.

Open forests, valleys, moist roadsides. Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hainan, Hubei, Hunan, Jiangsu, Jiangxi, Sichuan, Taiwan, Xizang, Yunnan, Zhejiang [India, Indochina, Japan, Malaysia, Nepal, Thailand].