Tuberous and wax begonias are two of the most popular begonia varieties and each is very different from the other. Tuberous begonias, just like their name implies, have tubers as their underground root structures, rather than fleshy, fibrous roots like other begonias. Tuberous begonias are started indoors in the late winter or early spring and transplanted outdoors after the last frost. They typically bloom three to five months after they are started indoors.
Fill a planting flat with 1 inch of moist peat moss or vermiculite as the medium. If the tuberous begonias were in winter storage, you can use the same medium in which they were stored. Otherwise, if you just obtained your tuberous begonias, use a new medium rather than one that was used elsewhere.
Lay the tuberous begonias in the flat, but not touching. The sides with the hollow sections or depressions are the tops.
Cover the tuberous begonias with moist peat moss or vermiculite. They only need to be covered a little bit.
Place the flat in an area that receives indirect light and is around 70 degrees F. Keep the medium slightly moist. However, do not water the tuberous begonias so much that the hollow section fills with water.
Wait until the tuberous begonias reach a height of 1 to 2 inches. Replant them in a similar manner, but individually, in 4- to 6-inch pots. Continue to water them and wait until after the last spring frost when they can be transplanted outdoors in a shady location.