Wild Oat

In Great Britain and/or Ireland:
Foodplant / parasite
Blumeria graminis parasitises live Avena fatua

Foodplant / parasite
amphigenous, scattered or in patches uredium of Puccinia coronata parasitises live leaf of Avena fatua
Remarks: season: summer

Foodplant / parasite
amphigenous uredium of Puccinia graminis f.sp. avenae parasitises live leaf of Avena fatua

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.

Avena fatua L. Sp. PI. 80. 1753
Avena fatua var. glabrala Peterm. Fl. Bienitz 13. 1841. (Type from Europe.)
Culms erect, rather stout, 30-75 cm. tall; leaves numerous, the blades flat, scabrous, elongate, usually 4-8 mm. wide; panicle loose and open, 15-30 cm. long, the slender branches usually horizontally spreading; spikelets nodding; glumes 2-2.5 cm. long, broad, many-nerved, acuminate; florets 3, the rachilla disarticulating; lemmas and rachilla-joints conspicuously hispid below with tawny to brown hairs, strongly nerved toward the acute, toothed apex, 1.5-2 cm. long, the rather stout awn 3-4 cm. long.
Type locality: Europe.
Distribution: Weed in cultivated ground and waste places, common on the Pacific coast; native of Europe.

Annuals, Terrestrial, not aquatic, Stems nodes swollen or brittle, Stems erect or ascending, Stems geniculate, decumbent, or lax, sometimes rooting at nodes, Stems caespitose, tufted, or clustered, Stems terete, round in cross section, or polygonal, Stem internodes hollow, Stems with inflorescence less than 1 m tall, Stems with inflorescence 1-2 m tall, Stems, culms, or scapes exceeding basal leaves, Leaves mostly cauline, Leaves conspicuously 2-ranked, distichous, Leaves sheathing at base, Leaf sheath mostly open, or loose, Leaf sheath smooth, glabrous, Leaf sheath and blade differentiated, Leaf blades linear, Leaf blades 2-10 mm wide, Leaf blades 1-2 cm wide, Leaf blades mostly flat, Leaf blades mostly glabrous, Leaf blades scabrous, roughened, or wrinkled, Ligul e present, Ligule an unfringed eciliate membrane, Inflorescence terminal, Inflorescence an open panicle, openly paniculate, branches spreading, Inflorescence solitary, with 1 spike, fascicle, glomerule, head, or cluster per stem or culm, Inflorescence lax, widely spreading, branches drooping, pendulous, Inflorescence branches more than 10 to numerous, Flowers bisexual, Spikelets pedicellate, Spikelets laterally compressed, Spikelet 3-10 mm wide, Spikelet less than 3 mm wide, Spikelets with 3-7 florets, Spikelets solitary at rachis nodes, Spikelets all alike and fertille, Spikelets bisexual, Spikelets disarticulating above the glumes, glumes persistent, Rachilla or pedicel hairy, Glumes present, empty bracts, Glumes 2 clearly present, Glumes equal or subequal, Glumes equal to or longer than adjacent lemma, Glume equal to or longer than spikelet, Lemma similar in texture to glumes, Lemma coriaceous, firmer or thicker in texture than the glumes, Lemma 5-7 nerved, Lemma 8-15 ner ved, Lemma body or surface hairy, Lemma apex dentate, 2-fid, Lemma distinctly awned, more than 2-3 mm, Lemma with 1 awn, Lemma awn 2-4 cm long or longer, Lemma awn subapical or dorsal, Lemma awn twisted, spirally coiled at base, like a corkscrew, Lemma awn once geniculate, bent once, Lemma margins thin, lying flat, Lemma margins inrolled, tightly covering palea and caryopsis, Lemma straight, Callus or base of lemma evidently hairy, Callus hairs shorter than lemma, Lemma surface pilose, setose or bristly, Palea present, well developed, Palea membranous, hyaline, Palea shorter than lemma, Palea 2 nerved or 2 keeled, Stamens 3, Styles 2-fid, deeply 2-branched, Stigmas 2, Fruit - caryopsis, Caryopsis ellipsoid, longitudinally grooved, hilum long-linear, Caryopsis hairy all over.

Avena fatua is a species of grass in the oat genus. It is known as the common wild oat. This oat is native to Eurasia but it has been introduced to most of the other temperate regions of the world. It is naturalized in some areas and considered a noxious weed in others.

Avena fatua is a typical oat in appearance, a green grass with hollow, erect stems 1 to 4 feet (30–120 cm) tall bearing nodding panicles of spikelets. The long dark green leaves are up to a centimeter wide and rough due to small hairs. The seedlings are also hairy. The seed kernel is thinner, longer, darker and hairy when compared with the seed of the common cultivated oat (Avena sativa). This species and other wild oats can become troublesome in prairie agriculture when it invades and lowers the quality of a field crop, or competes for resources with the crop plants. It takes very few wild oat plants to cause a significant reduction in the yield of a wheat or cultivated oat field, even though the seeds are a type of oat.