How do I overwinter tuberous begonias?
Carefully dig up the tuberous begonias within a few days of a killing frost. Leave a small amount of soil around each tuber. Cut off the stems about 1 inch above the tubers. Place the tubers in a cool, dry area to cure for 2 to 3 weeks. After curing, shake off the remaining soil. Place a layer of peat moss, vermiculite, or sawdust in a small cardboard box. Lay the tubers on the storage medium, then cover the tubers with additional peat, vermiculite, or sawdust. Store the tubers in an area with a temperature of 40 to 50 degrees Fahrenheit. Do not allow the tubers to freeze.