For the most part, begonias are tender perennials, meaning in an area that freezes in winter, there's a good chance they'll die off. If you live in a warmed climate, you can just leave them in the ground or pot outdoors for the winter and expect they will bloom again the next spring and summer. It does freeze where I live. It's recommended that gardeners in my area dig up their begonia bulbs/tubers and keep in a cool but frost-free spot for the winter.
Last spring, I picked up this hanging basket (empty) from a free pile in my neighborhood. I went to the garden center at Fred Meyer with the hope of finding a begonia plant. They were selling pre-filled begonia baskets for $33 each. I bought a single plant for $3.50 and brought it home to pot in this basket. I enjoyed blooms July, August, and early September. At the end of the season, I decided I wanted to try to save the plant to put out again the next spring.
I didn't need to dig up the bulb, however. Since I planted mine in a pot, I decided to just bring the pot into the garage (where it never freezes, but stays cool). Just before the first frost I brought my begonia, pot and all, into the garage, set it on the concrete floor about 5 or 6 feet from the door to the house and the furnace and water heater, and gave it no thought all winter. I forgot to get it back out until late spring. I was half-expecting it to not come back to life. But I placed it in a spot where I'd remember to water what looked like a pot of dirt. Low and behold, a tiny shoot began to emerge from the soil, then another shoot, and another.
The plant has doubled in size. It looks like the bulb could potentially be divided into two plants. I'll leave them both in this pot together just as they are for at least one more season. Begonias like to be little crowded.
So the plant has now begun to bloom. I'll enjoy what it gives me the rest of this summer, then bring it into the garage again in early to mid October. I suspect many folks treat begonias like annuals and plan on replacing them the next year. I might have, too, if I hadn't read that these could overwinter in a garage or cellar and if I'd had to dig them out of the ground on some chilly autumn day. As it worked out, it was super simple for me to bring the whole pot into the garage to leave it until spring.
