Avena L.
Type species: A. sativa L.
Annuals or biennials, with solitary culms or tufted. Leaf-sheath chartaceous, striate, rounded. Ligule membranous. Auricles 0. Leaf-blade flat, rarely convolute. Panicle loose to sometimes contracted or secund with large nodding spikelets. Spikelets with 1-6 ⚥ florets and 1-(2) ♂ or rudimentary florets; disarticulation below each floret, or only above glumes, or not at all in cultivated spp.; rachilla prolonged. Glumes usually equal and equalling spikelet, 3-11-nerved, rounded, lanceolate, acuminate, herbaceous to thinly chartaceous with thick scarious margins. Lemma usually coriaceous at maturity, bidentate to biaristulate and then rarely with 2 additional setae, rarely subentire; awn middorsal, stout and geniculate, column usually twisted, cultivated spp. often with reduced awns or awnless. Palea tough, ≤ lemma, 2-keeled, keels ciliate. Lodicules 2, linear-lanceolate, or unequally bilobed or with a rudimentary side-lobe. Callus hairy or glabrous. Stamens 3. Ovary hairy; styles free. Caryopsis terete, grooved; embryo relatively small to very large; hilum linear; endosperm solid.
Key
c. 30 spp. of Europe, western and central Asia, North and north-eastern Africa, naturalised in many temperate regions. Naturalised spp. 5; transient sp. 1.
Edgar, E. Proc. 33rd N.Z. Weed and Pest Control Conf. 230-236 (1980) discussed characters distinguishing species of Avena growing wild in N.Z.
The genus was monographed by Baum, B. R. Canada Dept Agric. Monogr. 14: 1-463 (1977) and his treatment is followed here.
