A tuberous begonia is a popular plant that grows to a height of 10 to 12 inches (25 to 30.5 cm) and produces large double blooms that easily reach six inches (15 cm) in width. They grow well in indirect sunlight with some shade and require moist soil. Tuberous begonias are easy to propagate with different methods. The most popular ways are by dividing adult plants into several smaller plants and by rooting a cutting taken from an existing plant.
Place a clay pot that is two to three inches (5 to 7.5 cm) in diameter and has no drain holes inside of a 10-inch (25-cm) plastic pot.
Fill the plastic pot with an equal mixture of potting soil and peat moss. Pack it down to make it firm and water well enough to make it damp. Fill the clay pot with water.
Cut sections of an established tuberous begonia that are four to six inches (10 to 15 cm) long and contain several leaf nodes. Strip all leaves with the exception of the top ones.
Dip the cutting into a powdered rooting hormone and tap to remove extra. Plant the cutting deeply enough in the plastic pot to allow it stand on its own.
Enclose the entire pot in a large plastic bag and close the bag. Place the pot in an area where it will be warm and receive bright, indirect light.
Check for roots after four weeks have passed. Open the plastic bag slightly more each day to allow the plant to become slowly accustomed to normal conditions.
There is no need to water the plants while the bag is closed. Check the clay pot often to be sure it still has water and refill as necessary. Once roots are well established and the plastic bag is removed, the plants are ready to be moved to a normal pot to wait to be planted outdoors in spring.