Tuberous begonias are valued for their nearly never-ending types of big, showy flowers in single, double and ruffled varieties, in solid or variegated shades of white, pink, orange, red, salmon and yellow. Tuberous begonias are especially popular because they're one of the few long summer bloomers that will thrive in shady areas. Tuberous begonias can successfully be propagated by leaf cuttings. Take leaf cuttings from tuberous begonias in early spring.
Fill a planting container with a potting medium made of damp sand, perlite or a combination of both. To dampen the potting medium, put the sand or perlite in a bowl or bucket and add water, mixing until the potting medium is damp through but not soggy.
Use a clean, sharp knife or a razor blade to cut a healthy leaf from the tuberous begonia, along with 1 to 1 1/2 inches of the stem. Be sure to wipe all cutting tools with rubbing alcohol to prevent passing bacteria on to the leaf cutting.
Insert the cut end of the tuberous begonia leaf in the potting medium. Place the container in a ziplock bag, and close the bag.
Place the container in a warm, sunny spot away from direct sunlight or hot windows. The plastic bag should keep the environment humid, but if the soil dries out, open the bag and mist the soil.
Watch for the begonia leaf to form new plantlets at the base of the leaf. When the plantlets appear, remove the container gradually from the plastic bag. For the first 2 to 3 days, poke a few holes in the bag. For the next 2 to 3 days, open the top of the bag, and after that remove the container from the bag. The original leaf can be discarded.
Place the container in indirect sunlight. Keep the potting medium damp, but don't water excessively, as too much water can rot the begonia. Plant the tuberous begonia outdoors when the weather has warmed in spring, after all danger of frost has passed.