Rex begonia is a variety grown predominantly for its interesting and colorful foliage. Native to the forest understory, Rex begonia is intolerant of direct sun, making them a striking accent plant for the shade garden. Hardy to USDA zone 9, gardeners in cooler regions can grow their Rex begonia indoors. If grown indoors, provide the Rex begonia with humidity by placing its pot on a dish of pebbles, just barely covered with water.
Fill a planting pot with peat moss and pour water over it until the peat moss is completely saturated. Allow the pot to sit for 30 to 60 minutes. The soil should be moist, not wet. Create a hole in the peat moss for the cutting.
Cut a healthy leaf, including a small piece of the stem, from the Rex begonia.
Dip the end of the leaf into the rooting hormone and tap it gently on the side of the jar to remove any excess hormone.
Push the end of the leaf into the peat moss and gently pack the soil around it.
Place the pot in a plastic bag and then on the heat mat, set at 75 degrees Fahrenheit. Within three weeks you will see new plants starting at the base of the leaf. When these plants reach 2 to 3 inches in height, separate them from the leaf, discard the leaf and plant the new plants in a pot filled with equal parts of moist potting soil and peat moss.