Avena

One species is of major commercial importance as a cereal grain. Four other species are grown as crops of minor or regional importance.[4][9]

• Avena sativa – the common oat, a cereal crop of global importance and the species commonly referred to as "oats"
• Avena abyssinica – the Ethiopian oat, native to Ethiopia, Eritrea, + Djibouti; naturalized in Yemen + Saudi Arabia
• Avena byzantina, a minor crop in Greece and Middle East; introduced in Spain, Algeria, India, New Zealand, South America, etc.
• Avena nuda – the naked oat or hulless oat, which plays much the same role in Europe as does A. abyssinica in Ethiopia. It is sometimes included in A. sativa and was widely grown in Europe before the latter replaced it. As its nutrient content is somewhat better than that of the common oat, A. nuda has increased in significance in recent years, especially in organic farming.
• Avena strigosa – the lopsided oat, bristle oat, or black oat,[10] grown for fodder in parts of Western Europe and Brazil

Several species of Avena occur in the wild, sometimes as weeds in agricultural fields. They are known as wild oats or oat-grasses. Those growing alongside cultivated oats in agricultural fields are considered nuisance weeds, as, being grasses like the crop, they are difficult to remove chemically; any standard herbicide that would kill them would also damage the crop. A specific herbicide must be used. The costs of this herbicide and the length of time it must be used to reduce the weed are significant, with seeds able to lie dormant for up to 10 years.[4][11][12][13][14]

• Avena aemulans – European Russia
• Avena barbata – slender wild oat – from Portugal + Morocco to Tajikistan
• Avena brevis – short oat – central + southern Europe
• Avena chinensis – Germany, Austria; introduced in China, Belarus
• Avena clauda – Balkans, Middle East, Central Asia
• Avena eriantha – North Africa, Middle East, Central Asia, Caucasus
• Avena fatua – common wild oat – Europe, Asia, North Africa; naturalized in Australia, the Americas, various islands
• Avena longiglumis – North Africa, Israel, Spain, Portugal, Sardinia
• Avena maroccana – Moroccan oat – Morocco
• Avena murphyi – Morocco, Spain
• Avena prostrata – Morocco, Spain
• Avena saxatilis – Sicily and small nearby islands
• Avena sterilis – winter wild oat – Mediterranean, East Africa; temperate Asia; introduced in northern Europe, Australia, New Zealand, the Americas
• Avena strigosa – Spain, France, Portugal; introduced in other parts of Europe as well as in scattered locations in Australia, New Zealand, the Americas
• Avena vaviloviana – Eritrea, Ethiopia
• Avena ventricosa – North Africa, Middle East
• Avena volgensis – European Russia

Hundreds of taxa have been included in Avena at one time in the past but are now considered better suited to other genera:[4] Agrostis, Aira, Ampelodesmos, Anisopogon, Arrhenatherum, Avenula, Bromus, Calamagrostis, Capeochloa, Centropodia, Corynephorus, Danthonia, Danthoniastrum, Deschampsia, Festuca, Gaudinia, Helictochloa, Helictotrichon, Hierochloe, Lachnagrostis, Lolium, Parapholis, Pentameris, Periballia, Peyritschia, Rytidosperma, Schizachne, Sphenopholis, Stipa, Stipagrostis, Tenaxia, Tricholemma, Triraphis, Trisetaria, Trisetum, Tristachya and Ventenata.