The flowers normally appear in groups of three - one large male flower in between two smaller females. Multiflora types produce many stalks, leaves, and flowers are the simplest to raise. Grandifloras grow taller with more brittle stems which require staking. Hanging begonias are usually more difficult to grow. The size of the tuber determines the number of flowers that will be produced.
Smaller tubers are best for smaller containers or for mass plantings in a garden bed.
Start tuberous begonias in flats in March. Set outside only after there is no danger of frost. Plant the tuber with the concave side up, and cover with inch of soil mix. Most of the roots grow from the top rather than the base of the tuber. A gallon milk carton with one side removed is a good starter flat.