Wax begonia or Begonia x semperflorens is a popular shade annual. It forms compact mounds with flowers that include white, shades of pink, peach or red. The leaves are round and glossy and either bright green or bronze. They grow from 6 inches to a foot tall and wide. They are good for containers or shade gardens. Wax begonia starter plants can be bought at garden centers or they can start from seeds in the spring.
Begonia seeds are very small, almost dust-like. They require warmth (70 to 80 degrees Fahrenheit) and moisture to germinate. Seed-starting material is available at most local garden centers.
Seed-starting trays are ideal for planting small seeds and will make it easier to transplant them later. They should be started as seeds four to six months before the last spring frost. For begonias, place some coarse sphagnum moss or pebbles about a half inch deep. Then use either planting soil or a mixture of peat moss and sand with vermiculite on top. Sprinkle the seeds over the top. Do not cover the seeds with soil. Just cover the tray with a plastic top and set the container in a warm spot.
The seeds do not need much light at first. If the top of the container starts to collect condensation, it should be removed and wiped off and put back. Allow 14 to 20 days for germination to occur. Then move the containers to an area with some light. Keep the soil moist. As the seeds grow, gradually leave the top off for a few more minutes each day. Transplanting can take place when there are a couple leaves on the small plants.
Transplanting outdoors can't occur until the last frost of the season. The plants can be transplanted into pots or window boxes. They can also be used directly in an outdoor garden.
Planting Directly Outside
When planting begonias directly outside, plant them where it is part to mostly shady. The holes should be dug big enough to put the whole plant in without damaging the roots. After planting, water the plants and let the dirt settle around them. Begonias like well-drained soil with a pH of 6.0 to 8.0.
Begonias should be planted in partial shade. Deep shade will cause the plants to become spindly and not bloom plentifully. They will grow in sun but the soil must be kept moist. There are new hybrids now that are more heat-resistant and do better in the sun. The plants will grow better with a layer of mulch or leaves around them to help preserve the moisture. At the same time, don't let standing water collect as this can cause diseases and rot rooting.
Pests and Diseases
Begonias are a relatively problem-free plant. Rot root can occur if over watered. Otherwise, they are only occasionally bothered by spider mites or whiteflies. They are an easy to care for annual.