Avena
Avena is a genus of Eurasian and African plants in the grass family. Collectively known as the oats, they include some species which have been cultivated for thousands of years as a food source for humans and livestock. They are widespread throughout Europe, Asia and northwest Africa. Several species have become naturalized in many parts of the world, and are regarded as invasive weeds where they compete with crop production. All oats have edible seeds, though they are small and hard to harvest in most species. Ecology. "Avena" species, including cultivated oats, are used as food plants by the  larvae of some Lepidoptera species, including rustic shoulder-knot and setaceous Hebrew character. For diseases of oats, see List of oat diseases. Species. Cultivated oats. One species is of major commercial importance as a cereal grain. Four other species are grown as crops of minor or regional importance. Wild oats. 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. Species formerly included. Hundreds of taxa have been included in "Avena" at one time in the past but are now considered better suited to other genera: "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". Sociolinguistics. "Sowing wild oats" is a phrase used since at least the 16th century; it appears in a 1542 tract by Thomas Beccon, a Protestant clergyman from Norfolk. Apparently, a similar expression was used in Roman Republican times, possibly by Plautus. The origin of the expression is the fact that wild oats, notably "A. fatua", are a major weed in oat farming. Among European cereal grains, oats are hardest to tell apart from their weedy relatives, which look almost alike but yield little grain. The life cycle of "A. fatua  is nearly synchronous with that of common oat, and their relationship is an example of Vavilovian mimicry. Historically, growers could control the weed only by checking the crop plants one by one and hand-weeding. Consequently, sowing wild oats" became a phrase to describe unprofitable activities. Given the reputation of oat grain to have invigorating properties and the obvious connection between plant seeds and human "seed", it is not surprising that the meaning of the phrase became a reference to the destructive sexual liaisons of an unmarried young male, which result in unwanted children born out of wedlock. Avena Avena