Cover crops span a diverse array of plant types and species, and they can be used at various times of the year in the Southern Great Plains. For the sake of simplicity, we will group them by warm-season and cool-season. Typically, cool-season cover crops are planted in the fall on crop fields or overseeded into dormant warm-season perennial grass pastures. Warm-season cover crops are usually planted in the spring on crop fields. In Oklahoma and Texas, they can also be planted in late summer for fall growth prior to a killing frost. We have experimented with growing cover crops in various environments in the Ardmore, Oklahoma, area over the past several years. Following are some of our observations.