Hordeum, commonly called barley, is a grass genus of about 30 species native to temperate areas of the northern hemisphere and South America, and to South Africa. The genus is diverse, with some species considered invasive weeds, and others rare and endangered. One species, H. vulgare or common barley, is of extreme commercial importance, and is used for cereal, animal feed, and the manufacture of beer and whiskey.
H. vulgare was the first grain to be cultivated, and is among the most widely grown grains today. Beer made from barley is believed to be the first drink made by humans. The plant, native to the Fertile Crescent in western Asia, is resistant to drought and very adaptable, allowing it to be grown throughout temperate and tropical climates. It remained a dietary staple in European and Middle Eastern cultures into the medieval period.
Barley was highly culturally important throughout early human history. It has been used as currency, as a unit of measurement, in divination rituals, and in religious sacrifice. Today, in addition to its use in alcoholic beverages and food for people and livestock, barley is used as a natural algicide in garden ponds in England. It is also used in health foods, particularly as a natural sweetener. Barley malt syrup is thick, dark, and about half as sweet as refined sugar.
Arizona barley, or Hordeum arizonicum, is a wild species growing throughout the southwestern United States and northern Mexico. It grows in wet areas within the desert, and is moderately tolerant of salinity. H. depressum, also called dwarf barley or low barley, is native to the western United States, where it grows in moist areas. H. brachyantherum, or meadow barley, grows in coastal areas of eastern Russia and Newfoundland, as well as western North America.
Hordeum intercedens, commonly called bobtail barley or vernal barley, is native to southern California in the United States, and northern Baja California in Mexico. Like other North American Hordeum species, it grows in moist areas and tolerates saline soils. It is becoming increasingly rare.
Foxtail barley, or Hordeum jubatum, grows in the wild on North America and northeastern Siberia. It is cultivated as an ornamental plant, propagated by seed, and tolerates a variety of soil types. Its hardiness has caused H. jubatum to become naturalized well beyond its native range, even becoming an invasive weed in some areas.