Bob Earle, age 12, of Helena, Mont., for his question:

HOW DOES WINTER WHEAT DIFFER FROM SPRING WHEAT?

Winter wheat is planted in the fall and harvested the following spring or summer. Winter wheat gets a start before cold weather begins. Growth stops during the winter and then begins again in the spring.

Spring wheat is planted in the spring and ripens the same summer, usually a few weeks after the winter wheat. If spring wheat is planted in the fall, it will not live through the winter except in mild climates or during unusually warm winters.

If winter wheat is planted in the spring, it ordinarily will not head or produce a crop. Winter wheat needs fairly low temperatures so that it can develop properly during early growth.

Among important varieties of winter wheat grown in the United States are Triumph, Wichita, Pawnees, Cheyenne, Comanche, Knox and Seneca.

Among important varieties of spring wheat are Selkirk, Lee, Thatcher, Conley, Rescue, Rushmore and Centana.