Have you put off growing sweet potatoes because you think it may not be warm enough in your area? If so try growing them in containers. You can start them indoors and then move them outside with a good growth on them and instead of putting them into the ground, plant them in large containers. This will help the sweet potatoes because the container will drain better and the soil around the roots will be warmer that it would be if they were planted in the ground and sweet potatoes like it a little warmer.
Garden Of Eaden tells you how to grow your sweet potatoes in containers, what sort of soil to use and when you should harvest the potatoes. You can get a jump start on growing your sweet potatoes by learning how to Start Sweet Potato Slips at home. Then just plant the slips inside untill it is warm enough to transfer them to your containers outdoors.