From 15 to 20 or more inches of precipitation are necessary for annual cropping. In some areas with not more than 10 to 15 inches of precipitation wheat is grown once in 2 years, with the land kept free of vegetation one of the years to accumulate moisture in the soil. The wheat plant is an annual grass. It is mainly grown as a winter annual in milder climates, with seeding in the fall and harvest from June through August depending on the length of the winter. In areas with rigorous winter climates it is mainly spring seeded.
Planting is as earlv as soil can be worked, and harvest is in late summer and early fall.
In early growth stages the wheat plant consists of a much compressed stem or crown and numerous narrowly linear or linear-lanceolate leaves. Leaves are mainly near glabrous. Buds in the leaf axils below the soil surface grow into lateral branches termed tillers. From both the main crown and the tillers, elongated stems develop later and terminate in a spike or head in which the flowers, and finally the seed or grain, develop. In fall-seeded wheat the plant usually remains in the rosette stage throughout the fall and winter, sending up the elongated stems in late spring.