Description: Tufted annuals.
Leaves with ligule membranous; blade rolled in the bud, narrow, flat.
Inflorescence a panicle, usually open.
Spikelets pedicellate, large, pendent, disarticulating above the glumes and sometimes between the lemmas, the florets being retained in the cultivated species; florets 2 or 3, rarely more, bisexual or the uppermost male. Glumes equal to unequal, acute, rounded on the back, 5–11-nerved, with shiny scabrous margins. Lemmas stiff, shorter than the glumes, acute, with 2 bristles or teeth at the apex, 5–9-nerved, bearing a usually bent and twisted dorsal awn attached about the middle of the back (sometimes the awn absent). Palea shorter than the lemmas, 2-keeled, 2-toothed.
Distribution and occurrence: World: c. 27 species, Northern Hemisphere. Australia: 8 species (naturalized), all States.
This important genus includes A. sativa, Common Oats, and several species, such as A. fatua, that have become weeds of cereal crops as a consequence of modern agricultural practices. Key from Wheeler et al. (1990).
Text by S. W. L. Jacobs & S. M. Hastings
Taxon concept:
Taxa not yet included in identification key
Avena fatua x sativa
| | Key to the species | |
| 1 | Lemma terminating in 2 fine bristles 3–12 mm long | 2 |
| Lemma with 2 small teeth or lobes less than 2 mm long | 3 |
| 2 | Rachilla not disarticulating between the florets at maturity (florets separated by fracturing the rachilla); bristles on lemma often with lateral teeth; glumes 7–9-nerved | Avena strigosa |
| Rachilla disarticulating between florets at maturity; bristles on lemma usually without lateral teeth; glumes 9- or 10-nerved
Back to 1 | Avena barbata |
| 3 | Lemmas (at least the lower 2) conspicuously hairy in the lower part; awn twisted and geniculate | 4 |
| Lemmas glabrous or with a few hairs at the base and at the sides; awn often straight or not strongly geniculate and scarcely twisted
Back to 1 | 6 |
| 4 | Rachilla disarticulating above the glumes but not between the florets at maturity so that the florets fall as a unit or separate by fracture of the rachilla; spikelets 25–45 mm long | 5 |
| Rachilla disarticulating above the glumes and between the florets at maturity; spikelets 18–25 mm long
Back to 3 | Avena fatua |
| 5 | Lowest lemma 25–33 mm long; ligule 6–8 mm long; awn stout, 6–9 cm long | Avena sterilis |
| Lowest lemma 18–25 mm long; ligule 3–4 mm long; awn slender, 3–6 cm long
Back to 4 | Avena ludoviciana |
| 6 | Spikelets with 2 or 3 florets; most of the rachilla remaining with the lower floret; awn, when present, with a distinct column | Avena sativa |
| Spikelets usually with 3 florets (sometimes 4); most of the rachilla remaining with the upper floret(s); awn without a distinct column
Back to 3 | Avena byzantina |
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