Tuberous begonias are a tender plant variety native to South Africa and tropical areas in South America. The plant tubers must be wintered indoors if you want to replant them in spring. Starting the plants indoors during late winter will produce an earlier blooming plant that can be placed outdoors once there is no longer a risk of frost. Tuberous begonias are commonly planted in containers and placed in shaded locations.
Purchase begonia tubers in the late winter season. Begonia tubers from a previous growing season that are being stored indoors can also begin their growing process in late winter.
Prepare a plant growing flat or container with an even mixture of peat moss and perlite that is dampened with water. Place the tubers upright in the soil so the side with the depression is facing upward. Lightly cover the tubers with soil.
Place the planting flats in an area that is approximately 70 degrees F and has indirect sunlight. Keep the soil moist but not wet to prevent tuber rot.
Transplant the tubers to 6-inch plastic growing pots once the tubers produce stems that are 1-inch in height. This process takes approximately one month.
Place the transplanted pots in a location with bright light or under indoor growing lights. This will assist the plant in producing sturdy stem growth.
Thin the shoots when they reach 3-inches in height if a plant with large flowers is preferred. Keep two to three stems on small tubers and three to six on large tubers. Do not thin tubers that will be planted in hanging baskets.
Harden the plants several weeks prior to last frost. Place the plants in a warm location for more time each day, and bring them in at night. Continue this process until there is no longer a frost danger.
Transplant the begonia plants to their permanent growing containers once they are placed outside.