Avena sativa (oat)

The spikelets consist of 2 or 3 fertile florets, and are wedge-shaped, laterally compressed, 22–27 mm long and persistent on the plant. The glumes (empty bracts that enclose the florets) extend past the tip of the florets, and are thinner than the fertile lemma (principal bract enclosing the flower). The upper and lower glumes are both lance-shaped, 22–27 mm long, membranous, without keels and 7–9 -veined.

The fertile lemma is lance-shaped, leathery, 15–17 mm long, much thinner above, without a keel and is 7–9 -veined. The surface of the lemma is scaly, rough above and hairless. The flowers have three anthers and an ovary which is hairy all over. The fruit is a caryopsis (simple dry fruit) with an adherent pericarp (outer layer). The fruit is hairy all over and has a linear hilum (scar marking the point of attachment).

Being tolerant of low soil fertility and frost, and requiring low external inputs (such as fertilizers), Avena sativa has been suggested as a potential food and fodder crop for resource-poor farmers in areas such as the highlands of tropical Africa. In some areas, however, such as in Victoria, Australia, parts of North America, and in the Karoo-Namib region of southern Africa, wild oats have become invasive and are a threat to native species of grasses and herbs.

Red oat or Turkey oat, Avena byzantina, is also descended from A. sterilis. Although sometimes considered to be the same species as A. sativa, red oat is genetically distinct and has a different distribution including, as the name suggests, Turkey. However, red oat has been largely replaced by A. sativa in recent years.

Four minor cultivated species are derived from wild forms of A. strigosa grown in the western Mediterranean. Bristle oat, A. strigosa, is a fodder plant in central and northern Europe, and is still grown in the Shetland Islands, but is almost extinct. A. brevis and A. hispanica are now very rare crops of southwest Europe. A. nuda is a naked form of oat that threshes free of the tough husk. It has low yields and is not widely cultivated.

A. abyssinica is only found in Ethiopia. It grows as a tolerated weed of other cereals, mainly barley, and is now in the course of domestication.