Crops produced for sale are called cash crops. Many commercial farms grow only one cash crop. These farms are known as one-crop, or single-crop, farms. Much of the world's wheat is grown on huge one-crop farms on the North American Great Plains and in the former Soviet Union's region. Large single-crop farms in tropical and subtropical areas are often called plantations. Plantation grow such crops as bananas, coffee, rice, sugar cane, and tea.