Sweet potatoes take 90 to 100 days of growing. On a warm day dig them up and let them dry on the ground...................when dirt is dry BRUSH the dirt off..............let them dry a little more........................they can be stored in a root cellar 34 to 40 degrees or in a cool dark basement for 6 months. If they are not all used by that time they will start to get little bumps on them and then you can cut out leaving room around the bud and replant them for the next crop. Happy Spring!