None of the native species is in cultivation. Barley plants are annual grasses which may be either winter annuals or spring annuals. Winter annuals require a period of exposure to cold in order to produce flowers and set seeds, thus are planted in the fall. They form a rosette type of growth in fall and winter, developing elongated stems and flower heads in early summer. If seeded in the spring they fail to produce seed heads.
Winter varieties form branch stems or tillers at the base so several stems rise from a single plant.
The winter varieties of barlev are more hardy than winter oats, but somewhat less hardy than winter wheat. Around a fourth of the barley grown in the United States is of winter varieties. Spring varieties do not require exposure to cold in order to devlop seed heads. Also, they do not have a typical rosette stage and so develop fewer tillers than winter varieties. They are the only kind adapted to areas with very cold winters.