Barley, common name for any of a genus of cereal grass, native to Asia and Ethiopia, and one of the most ancient of cultivated plants (see Grasses). Its cultivation is mentioned in the Bible, and it was grown by the ancient Egyptians, Greeks, Romans, and Chinese. It is now the fourth largest grain crop, after wheat, rice, and corn (see Crop Farming). In the United States and Canada, as well as in the greater portion of Europe, barley is sown in the spring. Along the Mediterranean Sea and in parts of California and Arizona, it is sown in the fall. It is also grown as a winter annual in the southern United States. Drought resistant and hardy, barley can be grown on marginal cropland; salt-resistant strains are being developed to increase its usefulness in coastal regions. Barley germinates at about the same temperature as wheat. The different cultivated varieties of barley belong to three distinct types: two-rowed barley, six-rowed barley, and irregular barley. The varieties grown in the United States are generally of the six-rowed type, in Europe the two-rowed type predominates, and the irregular type is found in Ethiopia. The finest malting varieties are the six-rowed and the two-rowed types.

Barley grain, hay, straw, and several by-products are used for feed. The grain is used for malt beverages (see Beer) and in cooking. Like other cereals, barley contains a large proportion of carbohydrate (67 percent) and protein (12.8 percent).

Annual world production of barley at the beginning of the 21^st century stood at 132 million metric tons, almost 25 percent less than in the late 1980s. By far the leading producer was Russia with 14 percent of world output; France was second with 8 percent, followed by Germany and Ukraine. In the United States, barley is grown in the western states. North Dakota led with 1.2 million metric tons, followed by Idaho, Montana, Washington, Colorado, Minnesota, and California.

Scientific classification: Barley belongs to the genus Hordeum, of the family Poaceae (formerly Gramineae). Two-rowed barley is classified as Hordeum distichon, six-rowed barley as Hordeum vulgare, and irregular barley as Hordeum irregulare.