No matter how it is planted or grown, a begonia tuber will end up entering a dormant state at some point during the year. Begonia tubers, however, can be stored over the winter months and replanted in the spring. The most important factor when storing a begonia tuber is to keep it completely dry. This is usually achieved by storing it in bags or materials that wick away moisture from the surface of the bulb. They also must be stored in a cool area, and they need to be checked regularly to ensure that no diseases, fungi or pests have started to affect them.
The first step in storing a begonia tuber is the drying process. After the tuber is out of the ground, it needs to be allowed to dry completely, preferably until the stems of the plant easily separate from the tuber. The disc-like bulbs should be cleaned of dirt, debris and any insects that might be on them, but with a dry towel or brush rather than water. Once completely dried, the tuber can be coated in a special sulfur powder that can prevent fungi from growing on the surface.
A dried begonia tuber needs to be stored in something that will protect it from environmental conditions such as dust, pests and cold drafts. At the same time, air needs to be able to circulate around the tuber. One common way to store a begonia tuber is to place it in a loosely closed paper bag. Another option is a perforated plastic bag, much like those used by commercial growers, that is filled with a light substance such as vermiculite.
Sometimes a bag is not necessary. A milk crate full of shredded newspaper can be used to store a begonia tuber. If the plant is grown indoors, then it can be left directly in the dry soil of the pot, as long as the pot is placed in a cool area. Even in regions where the ground might never receive a hard frost, tubers should still be stored indoors for the winter, because they otherwise run the risk of rotting in the ground as a result of rain.
The correct temperature for storing a begonia tuber is between 40° Fahrenheit and 50° Fahrenheit (about 4° Celsius to 10° Celsius). If multiple tubers are being stored, then they should be separated into different bags or spaced a good distance apart to make certain that any rotting or fungus does not spread quickly to the entire batch. The tubers should be checked regularly and bad or questionable ones should be removed or, at the very least, moved far away from the rest.