Plants annual. Culms 50-80 cm, erect. Sheaths glabrous
or sparsely pubescent, hairs 0.5-1 mm, sometimes confined to the margins; ligules of
the lower leaves 3-5 mm, those of the upper leaves 1.5-2.5 mm, acute; blades 12-25
cm long, 5-11 mm wide. Panicles 15-26 cm. Spikelets 30-40
mm, with 3-4(5) florets; disarticulation beneath each floret; disarticulation
scars of the lower florets round to elliptic, those of the third and
fourth florets heart-shaped. Glumes subequal, 30-40 mm, 7-9-veined; calluses bearded,
hairs 3-5 mm; lemmas 14-26 mm, usually densely strigose below midlength,
varying to sparsely strigose or glabrous, veins not extending beyond the
apices, apices bifid, teeth sometimes shortly aristate, awns arising at
midlength; lodicules without lobes on the wing; anthers 2-3.2
mm. 2n = 42.
Avena occidentalis is native to the Canary Islands, coastal North Africa, and Saudi Arabia; it is now established in western North America from Oregon to northern Mexico. It is often confused with A. fatua, but differs in its longer, narrower spikelets, greater number of florets, and the heart-shaped disarticulation scars of the distal florets.