Winter wheat is a particular strain of wheat that is sown and germinates in the late autumn, stays insulated under snow during the winter months, and is harvested in late spring. Winter wheat can be grown in places where snow covers the ground enough to insulate the plants, such as the plains of the United States and Canada.
Winter wheat is usually planted into fields that recently grew spring wheat. The stalks are left in the field, leaving 'stubble' for the snow to cling to in the winter. As with any other plants, there are several variables that must be contended with in order to produce a good crop. With winter wheat, these variables are even more extreme, given the winter growing season. Seeds for most varieties of winter wheat must be placed roughly one inch into the ground. Closer to the surface, and the seedlings will be exposed to cold temperatures. The seeds then germinate during the last few weeks of autumn, and grow several inches above ground. This allows the plant to acclimate to the cold temperatures, which is important to the plants survival through the winter.
The plants spend the winter as small seedlings, hidden among the stubble and the snow. The layer of snow regulates the temperature of the plants, which must remain within a certain range in order for the plant to survive the winter. If the ground temperature becomes too warm, the plants will try and grow, and thus lose their ability to withstand the cold. If the ground temperature becomes too cold, it could damage, or perhaps kill the plants. These temperature ranges vary depending on the variety of plant.
The plants will begin to grow again when the snow cover melts and the temperature warms again. The melting snow gives moisture to the plants, which begin growing upward at a rapid pace. By June or July, the kernel of the wheat begins to dry out, and is then ready for harvest. The plants are cut, the kernels are removed, dried, and stored.
Winter wheat is popular among many farmers for several reasons. First, pesticides and herbicides are generally unnecessary, as the plants spend a majority of their life span covered by snow, which saves a considerable amount of money. The wheat also doesn't need to be heavily fertilized; only a small amount of fertilizer after the snow melts will provide a large boost to the plants. Planting winter wheat also puts the fields into production earlier than would be possible planting spring wheat or other cereals.
Resources:
http://www.usask.ca/
http://www.agric.gov.ab.ca/
http://www.ku.edu/