Description from Flora of China
Serrafalcus japonicus (Thunberg) Wilmott.
Annual. Culms erect, 40–90 cm tall. Leaf sheaths pubescent; leaf blades 12–30 cm × 4–8 mm, both surfaces pubescent; ligule 1–2.5 mm. Panicle effuse, 20–30 × 5–10 cm, nodding; branches 2–8, 5–10 cm, slender, each bearing 1–4 spikelets. Spikelets lanceolate-oblong, 12–20 × ca. 5 mm, yellowish green, florets 7–11, closely overlapping; rachilla internodes shortly clavate, ca. 2 mm; glumes subequal, keel scabrid, margins membranous, lower glume 5–7 mm, 3–5-veined, upper glume 5–7.5 mm, 7–9-veined; lemmas elliptic, 8–10 × ca. 2 mm in side view, herbaceous, 9-veined, usually glabrous, margins membranous with conspicuous angle at maturity, scabrid, apex obtuse, minutely 2-toothed, awned from 1–2 mm below apex; awn 5–10 mm, longer on upper lemmas than lower lemmas, base slightly flattened, conspicuously recurved at maturity; palea shorter than lemma, ca. 1 mm wide, keels stiffly ciliate. Anthers ca. 1 mm. Caryopsis 7–8 mm. Fl. and fr. May–Jul. 2n = 14.
Forest margins, roadsides, waste ground, river beaches; near sea level to 2500(–3500) m. Anhui, Gansu, Hebei, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Liaoning, Nei Mongol, Shaanxi, Shandong, Shanxi, Sichuan, Taiwan, Xinjiang, Xizang, Yunnan [Japan, Kazakhstan, Kyrgyzstan, Mongolia, Russia, Tajikistan, Turkmenistan, Uzbekistan; N Africa, SW Asia, Europe; introduced in North America].