In cold areas, start the tubers indoors about 6 weeks before you anticipate the last frost. Plant the tuber in potting soil, round side down, about 1" below the surface. Water well and then keep the soil moist but not soggy. Keep in a warm, semi-shady area. When all danger of frost has passed, transplant outdoors being careful not to disturb the roots.Keep in a warm, semi-shady area. When all danger of frost has passed, transplant outdoors being careful not to disturb the roots.
In the garden, begonias need rich, porous, well-drained soil and shelter from wind. Space 12" apart in shade or partial shade. Keep the soil evenly moist and fertilize at least once a month. Tuberous begonias should be dug and immediately given a bath after they are lifted. They should be stored over the winter in shallow, open trays. If there may be mice or other rodents, place a wire covering over the open trays. Hardy in Zone 10.