I associate tuberous begonias with California. Tuberous begonias are the ones that look like roses, but come in saturated colors like orange, scarlet, blood-red and daffodil yellow. The little bedding plants you see around town are fibrous begonias, and I’m not talking about those.
I recently potted up my begonia tubers, something I do every year in March. They’re not cold weather plants, so every fall I stop watering them, then when the soil is dry, I carefully remove the tuber and put it in the garage to overwinter. I don’t seal it up or cover it with soil, although sometimes I leave it in the pot in was growing in, sitting on top of the soil. Each spring when I bring them out, most are starting to sprout.
In Capitola there was once a begonia festival, and a nursery called Antonelli’s, where you could see a forest of hanging begonias in different colors. It’s gone now, but in late spring you can find begonia tubers in local nurseries like Yamagami’s. They’re not especially difficult to grow – if you place them in dappled shade, fertilize them and don’t overwater. When the plants start blooming, you'll notice that there are two types of flowers, double and single. The double flowers are male and the single flowers are female. Pinch off the single flowers and you'll get better yields of the males - they're the showy, double blooms you want.