Annual 1-2 m tall. Leaves to over 50 cm long with ligules to 5 mm long. Inflorescence an open panicle that is of variable size and degree of openness. Spikelets 1.8-2.5 cm long with 1-4 florets.

Temperate regions

6-7 species are cultivated, mainly A. sativa, a cultigen domesticated around the Mediterranean about 3000 years ago and the source of a range of weedy forms. The commercial Oat is believed to be derived from A. fatua L. that has jointed stalks between the spikelets, which are readily separated at maturity. A. fatua is an extremely common and widespread weed worldwide. In Australia it occurs on roadsides, mostly where hay is produced and transported.

Source: Spencer, R.; Aldous, D.; Stajsic, V.; McGeary, D (2005). Poaceae. In: Spencer, R.. Horticultural Flora of South-eastern Australia. Volume 5. Flowering plants. Monocotyledons. The identification of garden and cultivated plants. University of New South Wales Press.