Begonias grow 6 to 12 inches high and provide constant color throughout the growing season. When hard frosts come, however, they cannot survive the winter. In order to keep the same plant, you must help the begonia get through this time. This may take some extra effort on your part, but saves money if you want to plant a begonia again the following growing season. Knowledge of how to go about this will help you overwinter the plant properly.
Stop fertilizing by the end of July. Extra nitrogen after that point will encourage the plant to grow more leaves instead of storing its energy in the tuber. Taper off watering at the end of August. These two combined elements will help the plant go into dormancy.
Dig up the tubers when the foliage starts to yellow or after the first hard frost. Cut the tops of the plants within a few inches of the tubers with a knife or scissors. Place them indoors to dry--out of the sun--until the last bits of the stem are dry and loose.
Gently shake off dirt from the tubers. Pull off the loose stems and roots that remain. Do not wash the tubers.
Fill a cardboard box or perforated plastic bag with peat moss or vermiculite. Place the tubers inside of this container and store in an area with temperatures between 45 and 55 degrees F. A basement will usually do the trick.
Plant the tubers in shallow flats filled with peat moss or vermiculite in late winter. Place the flats in indirect light and keep the medium moist, but not wet, during this period.