DES MOINES, Iowa (AP) -- Researchers are studying how to increase U.S. production of canola, known primarily for the cooking oil the plant produces.

Most of the U.S. canola crop is grown in North Dakota, but the nation still imports much of it supply from Canada.

That has prompted the industry and researchers to encourage farmers to grow a winter variety of canola.

It wouldn't work everywhere, but Dale Thorenson, assistant director of the U.S. Canola Association, estimates farmers could grow canola on 4 to 5 million acres planted from the Carolinas to the Great Plains.

Farmers general get about the same price for canola as they do for soybeans.

The canola plant, recognizable for its yellow flowers, produces pods that are filled with seeds. When crushed, those seeds yield oil.