Begonias (S)
Zone 10
Begonias should be planted in a very shady area. Morning sun or filtered sun is acceptable. For earliest bloom, start the tubers indoors 6-10 weeks before last spring frost date. Firmly press the tubers, concave side up, into shallow flats or plastic trays filled with damp peat moss. Do not cover the tubers. Keep in a warm, 21°C-27°C (70-80°F) place and water sparingly until growth starts. If pink buds are not apparent on concave (top) side of tuber after several days, press tuber upside down into potting mix temporarily. Check, every day, and once pink buds appear, plant right side up as usual. Once active growth starts, set them in a bright spot protected from direct sun and keep soil evenly moist. When growth reaches 2-4 inches high, transplant to pots, allowing one bulb per 6 inch pot. Use a porous, peat based soil mix, covering the tubers with not more than 1 inch of soil. After all danger of frost is past, put the pots outside or transplant the begonias into the garden, setting them 12 inches apart.
All tuberous begonias demand well-drained but moisture-retentive soil. Never let them lack for water. Begonia stems are quite brittle and need protection from strong wind. Fertilize twice during the summer with a weak liquid organic fertilizer such as fish emulsion.
For hanging basket varieties, transfer the begonias from the flats directly into the baskets. A 12 inch basket will accommodate 1-3 tubers.
Before frost, bring pots indoors or dig up plants and let them dry. Remove withered foliage and store tubers over winter in dry peat moss, in a cool place indoors.
