Avena

L.
Treatment appears in FNA Volume 24. Treatment on page 734.
Plants annual or perennial. Culms 8-200 cm, erect or decumbent. Sheaths open; auricles absent; ligules membranous; blades usually flat, sometimes involute, lax. Inflorescences panicles, diffuse, sometimes 1-sided, some branches longer than 1 cm. Spikelets 15-50 min, pedicellate, laterally compressed, with 1-6(8) florets; rachillas not prolonged beyond the base of the distal floret; disarticulation above the glumes, usually also beneath the florets, cultivated forms not disarticulating. Glumes usually exceeding the florets, membranous, glabrous, 3-11-veined, acute, unawned; calluses rounded to pointed, with or without hairs; lemmas usually indurate and enclosing the caryopses at maturity, 5-9-veined, often with twisted, strigose hairs below midlength, apices dentate to bifid or biaristate, usually awned, sometimes unawned, awns dorsal, usually once-geniculate and strongly twisted in the basal portion; paleas bifid or entire, keels ciliate; lodicules 2, free, glabrous, toothed or not toothed; anthers 3; ovaries hairy. Caryopses shorter than the lemmas, concealed at maturity, terete, ventrally grooved, pubescent; hila linear, x = 7.

Distribution

Conn., N.J., N.Y., N.Mex., Wash., Va., W.Va., Mich., Del., D.C, Wis., Idaho, Mont., Oreg., Wyo., Pacific Islands (Hawaii), Md., Mass., Maine, N.H., R.I., Vt., Fla., Tex., La., N.Dak., Nebr., Tenn., N.C., S.C., Pa., Alta., B.C., Greenland, Man., N.B., Nfld. And Labr. (Labr.), N.S., N.W.T., Ont., P.E.I., Que., Sask., Yukon, Calif., Nev., Puerto Rico, Colo., Alaska, Ariz., Ala., Ark., Ill., Ga., Ind., Iowa, Okla., S.Dak., Ohio, Utah, Mo., Minn., Kans., Miss., Ky.

Discussion

Avena, a genus of 29 species, is native to temperate and cold regions of Europe, North Africa, and central Asia; it has become nearly cosmopolitan through the cultivation of cereal oats, and the inadvertent introduction of the weedy species. Six species have been introduced into the Flora region.

Reports of Avena strigosa Schreb. from California are based on misidentifications. The specimens involved belong to A. barbata.

Key

1 Florets not disarticulating from the glumes, remaining attached to the plant even at maturity; calluses glabrous Avena sativa
1 Florets disarticulating at maturity, only the glumes remaining attached; calluses bearded. > 2
2 Florets falling from the glumes as a unit Avena sterilis
2 Florets falling separately > 3
3 Lemma apices biaristate, 2 veins extending 2-4 mm beyond the apices Avena barbata
3 Lemma apices erose to bifid, the veins not extending beyond the apices. > 4
4 Spikelets with 2(3) florets; disarticulation scar of the lower florets in a spikelet round to oval or triangular, that of the third floret, if present, similar Avena fatua
4 Spikelets with 2-4(5) florets; disarticulation scar of the lower florets in a spikelet round to elliptic, those of the third and fourth florets (and sometimes the second) heart-shaped. > 5
5 Glumes 15-23 mm long Avena hybrid
5 Glumes 28-40 mm long Avena occidentalis