Dahlias, tuberous begonias, and other tender perennials are attractive plants for the home landscape. The "bulbs" (actually tubers, rhizomes, and other structures) of tender perennials are usually planted directly outdoors in spring. However, these attractive ornamentals can be enjoyed for longer periods by starting them indoors in late winter.
Plant tubers indoors about 8 weeks before the average last spring frost in your area. When planting the tubers, place the concave or indented side upward. The rounded side is the bottom. Cover the tubers with 1/2 to 1 inch of potting soil. Water well. Then place the containers in a warm, 70°F location. Since the tubers are susceptible to rotting, keep the potting mix moist, but not wet.
Plant caladium tubers indoors 4 to 6 weeks before the average last frost date in your area. Tubers should be planted 1 to 2 inches deep. When planting the tubers, place the knobby side up. The knobs are the tuber's eyes or buds. After planting, place the containers in a warm, 75 to 80°F location to facilitate sprouting.
Start canna rhizomes indoors 4 to 6 weeks before the average last frost date in your area. Plant the cannas in large pots. The rhizomes should be covered with 3 to 4 inches of potting soil.
Plant dahlias indoors 6 to 8 weeks before the intended outdoor planting date. Pot up the dahlia tubers in large pots using a well-drained potting mix. Cover the tuber with 1 inch of soil, but leave the dahlia's crown exposed at the surface of the potting mix. Dahlia tubers are susceptible to rotting. Keep the potting mix moist, but not wet.
Start elephant's ear indoors 6 to 8 weeks before the average last frost date in your area. Plant the tubers 1 to 2 inches deep. Foliage may not appear for several weeks as elephant's ear tubers are often slow to sprout.
Plant calla lily rhizomes 1 to 2 inches deep in a well-drained potting mix about 6 to 8 weeks before the average last spring frost in your area. After potting, water well and place the containers in a warm, 70 to 75°F location. Keep the potting mix moist, but not wet.
When foliage appears, move the plants to a sunny window or place them under fluorescent lights. Before planting outdoors, harden or acclimate the tender perennials to outdoor growing conditions. Initially, place the plants in a shady, protected location and then gradually expose them to longer periods of sunlight. After they have been hardened, plant the tender perennials in their proper location.