Wild Oat

This is a noxious weed, especially in fields of wheat and cultivated oats, native to Europe and C and SW Asia, but now spread throughout temperate regions of the world.

Culms 30-60 cm tall. Blades linear, 10-15 cm long by 5-15 mm wide; ligule chartceous, tongue-shaped, minutely hispid on backside, 2.5 mm long. Panicle open, compound, about 10-30 cm long. Spikelets nodding, with more than 2 florets, falling off when mature, 1.4-3 cm long; glumes chartaceous, nearly equal, rounded on the backside; the lower 11-nerved, sometimes connected with tessellate nerves; the upper 9-nerved, aute; lemma densely bearded on backside, with a long geniculated awn arising from the backside; palea flattened, 2-keeled, margins ciliate. Caryopsis hairy; hilum linear.

Annual. Culms erect or geniculate at base, 50–150 cm tall, unbranched, 2–4-noded. Leaf sheaths glabrous or basal sheaths puberulous; leaf blades 10–30 cm, 4–12 mm wide, scabrid or adaxial surface and margins pilose; ligule 1–5 mm. Panicle narrowly to broadly pyramidal, 10–40 cm, nodding; branches scabrid. Spikelets 1.7–2.5 cm, florets 2 or 3, all florets awned; rachilla easily disarticulating below each floret at maturity, each floret with a bearded callus, internodes hirsute or glabrous; glumes lanceolate, subequal, herbaceous, 9–11-veined, apex finely acute; callus hairs up to 4 mm; lemmas 1.5–2 cm, leathery, glabrous to densely hispid in lower half, green and scaberulous above, awned from near middle, apex shortly 2–4-toothed; awn 2–4 cm, geniculate, column twisted, blackish brown. Fl. and fr. Apr–Sep. 2n = 42.

Annual; culms 30-150 cm high, erect or geniculately ascending, stout, simple. Leaf-blades 10-45 cm long, 3-15 mm wide, glabrous, rough; ligules up to 6 mm long. Panicle nodding (sometimes subsecund), narrowly to broadly pyramidal, 10-40 cm long and up to 20 cm wide, loose with rough spreading branches. Spikelets pendulous, 18-30 mm long, 2-3-flowered, the rhachilla articulated beneath each floret; glumes lanceolate, finely acute; lemmas 12-25 mm long, densely bearded around the callus with hairs up to 4 mm long, stiffly hairy (or completely glabrous) and finally brown in the lower two-thirds, green and rough above, unequally and shortly 2-4-toothed at the apex; awn 2.5-4 cm long, geniculate, the column dark brown.

Native to Europe and Western Asia, widely spread in all Eastern Asia.

Anhui, Fujian, Guangdong, Guangxi, Guizhou, Hebei, Heilongjiang, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Nei Mongol, Ningxia, Qinghai, Shaanxi, Sichuan, Taiwan, Xinjiang, Xizang, Yunnan, Zhejiang [Afghanistan, Bhutan, India (Sikkim), Kazakhstan, Kyrgyzstan, Nepal, Pakistan, Russia, Tajikistan, Turkmenistan, Uzbekistan; N Africa, SW Asia, Europe].

Weed of cultivated fields, grassy mountain slopes, roadsides and other disturbed places; below 4300 m.