毒麦 du mai

Annual. Culms tufted, erect or decumbent, slender to moderately robust, 20–120 cm tall, 3–5-noded. Leaf blades flat, thin, 10–25 cm × 4–10 mm, smooth or scabridulous on abaxial surface, margins scabrid, young blades rolled; auricles present or absent; ligule 0.5–2.5 mm, obtuse to truncate. Raceme stiff, straight, 10–30 cm; rachis thick, smooth or scabridulous, spikelets about their own length apart. Spikelets turgid, 0.8–2.5 cm, florets 4–10, rachilla internodes 1–1.5 mm, smooth, glabrous; glume linear-oblong, rigid, as long as spikelet, often exceeding florets, 5–9-veined, margins narrowly membranous, apex obtuse; lemmas elliptic to ovate, turgid at maturity, 5.2–8.5 mm, apex obtuse; awn usually present, stiff, scabrid; palea ciliolate along keels. Caryopsis very plump, length 2–3 times width, 4–7 mm. Fl. and fr. May–Aug. 2n = 14.

Fields of cereals, introduced. Anhui, Gansu, Hebei, Heilongjiang, Henan, Hunan, Qinghai, Shaanxi, Shanghai, Xinjiang, Zhejiang [N Africa, SW Asia, S Europe].

This is a noxious arable weed, widespread and naturalized in warm-temperate parts of the world (Darnel). The grains are often infected by a fungus (ergot) which produces the alkaloid temulin, causing poisoning when grazed by cattle or when present as a contaminant of flour.

Awnless or weakly awned variants can be distinguished at varietal rank.