Begonias that grow from bulbs are known as tuberous begonias, and they actually grow from tubers, not true bulbs. They are considered a summer bulb, however, and need warm weather and partial shade in which to prosper. Begonias grow well in containers, hanging baskets or in the ground. They can handle the summer in nearly any USDA zone inside the U.S., according to the University of Florida, but they need to be dug up and taken out of the ground come fall in colder regions.
Fill a flat box halfway full of peat moss or vermiculite and water it until it is moist but not soaking.
Dig a shallow hole for the begonia tubers in the peat moss or vermiculite with your hands. Place the begonia tuber into the hole with the indented side facing up. Cover the tubers with a thin layer of peat moss or vermiculite.
Place the box in a location with a constant 70 degree F temperature and indirect sunlight. Keep the peat moss or vermiculite moist but not wet.
Plant the begonias once they are 1 inch tall, after about a month. Fill a well-drained container with potting soil and dig a shallow hole large enough for the begonia tuber and its roots. Place the begonia into the hole with the stem facing upward and fill in the hole with potting soil.
Water the begonia well until water leaks out of the pot and place it in a partially sunny location for the best growth.