Calla lilies (Zantedeschia) are grown from bulbs, or rhizomes, which look like large, thick pieces of root. Although calla lily bulbs are usually planted directly into the ground, they grow well when started in pots indoors. Calla lilies make for great houseplants too, as their growing conditions are conducive to the indoor environment, allowing them to retain their lush foliage year-round. Even better, you don't have to wait until spring or worry about frost when planting calla lily bulbs indoors---you can plant them anytime of the year.
Plant the calla lily bulbs in well-drained potting soil. Plant the bulbs in individual pots that are 6 inches in diameter and have drainage holes in the bottom.
Make a small hole that is 4 inches deep. Plant the bulb horizontally with the growing side up. Cover the bulb with the potting soil and pat down.
Position the pots so they receive bright morning sunlight but are shaded in the late afternoon. Water until the soil is moist and the water is draining freely through the bottom. After the initial watering, water the bulbs sparingly until they sprout so that the soil is kept moist but never wet.
Fertilize the calla lilies once per month using an all-purpose fertilizer after the sprouts have begun to poke through the soil. Follow the dosage instructions on the fertilizer package. Also, after the lilies have started to grow, water them at least once per week to keep the soil moist at all times.
Repot the calla lilies into larger pots once each year as they grow. If you start out with a 6-inch pot, gradually increase the pot size each year until the calla lily is in a 12-inch pot.