Barley originally comes from the Near East and the eastern Balkan and is one of the oldest crop cereals used in Central Europe. It is found as long as 15,000 B.C. ago. In antiquity (800 B.C. – 600 A.D) it was planted in Mesopotamia and at the Nile, in the Neolithic (5,500 B.C.) also in Europe. Cultivated barley probably originated from natural mutants grown and nurtured by humans, so that seeds don’t immediately fall out with maturity.
Barley was cultivated up to 1800m elevation. It has little requirements for water, a short vegetation period and a broad temperature amplitude (from 5-10 degrees to 30 degrees soil temperature). The eared fruit with long awns is discriminated into two forms based on the ears, the two-row and multi-row forms. The two-row forms develop one corn per attachment site, which is fully and strongly developed. With the multi-row forms there are the corns per attachment site, which are less developed.
Wild barley (Hordeum vulgare ssp spontaneum)
Cultured barley (Hordeum vulgare sssp vulgare)
Two row barley (Hordeum vulgare f. distichon)
Multi row barley
Pearl barley (Hordeum vulgare f hexastichon)
Hordeum vulgare f agriochriton
Hordeum vulgare var coeleste L.
Hordeum vulgare var. trifurcatum (Schlechtendal) Alefeld
Two row barleys (usually summer barley) are used to make beer as brewery barley (malt). Four and six row barley are usually winter barley, which are planted in autumn and need vernalization to flower. Thanks to efficient use of winter humidity the yields are larger and the nutrients favourable for the use as animal food barley.

Literature
Miedaner, Thomas (2014): Kulturpflanzen: Botanik — Geschichte — Perspektiven. Berlin Heidelberg: Springer-Verlag. ISBN: 364255292-2
Schilperoord, Peer (2013) : Kulturpflanzen in der Schweiz – Gerste. Alvaneu Dorf: Verein für alpine Kulturpflanzen. ISBN 978-3-9524176-8-3
Zohary, Daniel; Hopf, Maria; Weiss, Ehud (2012): Domestication of plants in the Old World. The origin and spread of domesticated plants in Southwest Asia, Europe, and the Mediterranean Basin. 4. Aufl. Oxford: Oxford University Press. ISBN: 978-0199549061