You can start purchased or stored tuberous begonias in late winter or early spring (about 8 weeks before the last frost). Before planting, ready them for growth by placing them in a warm area (about 70 degrees Fahrenheit) with indirect sunlight. Within a few weeks, small buds should appear in the cupped area of the roots. After your tubers have sprouted, plant them in grow pots with a well-draining potting mix and water sparingly until each plant has one or two leaves.

After leaves have emerged, plant your tubers directly in the ground (about 8 to 12 inches apart) or in a container (about 5 inches apart) that has excellent drainage and cover them with about 1 inch of soil. Continue watering sparingly while the plants establish themselves.