A Rieger begonia is a hybrid cross between a fibrous and tuberous begonia. This variety is known by the name winter begonia because it can be brought indoors for winter blooming. The plant produces male and female double rose-shaped blooms with the male blooms dropping two to three days after opening. The Rieger begonia can be propagated by wintering the plant indoors and taking new shoot cuttings in spring.
Cut back the Rieger begonia plant within 3 inches from the crown in the fall before the first frost.
Reduce the amount of water given the plant and place it in a cool indoor location. Monitor the plant and lightly water if required. Begin to water the begonia normally in the spring to induce new shoot growth.
Take cuttings from the Rieger begonia once the shoots are longer than 5 inches. Cut a 4-inch section of growth just above a leaf node on a non-flowering stem.
Create a mixture of rooting soil by mixing equal portions of peat moss and perlite. Moisten the mixture to a level where water can not be squeezed out of the soil.
Dip the cut end of the stem in rooting hormone. Gently tap the end of the cutting to remove excess hormone.
Fill a 3-inch pot with rooting soil and stick the cut end of the stem into the soil. Cover the pot by placing it in a clear plastic bag making sure the plastic does not touch the cutting.
Monitor the cutting to prevent the soil from drying. Lightly mist the soil with water if necessary. Be careful to not get water directly on the cuttings.
Monitor the plant to watch for new plant growth. This is a sign the propagation was successful. Remove the plastic covering and continue to grow the cuttings until the root structure is strong enough to be transplanted.