Flowers as elegantly streamlined as italic script make calla lilies (Zantedeschia spp.) striking complements to the most casual or sophisticated interior decorating schemes. With proper growing conditions, the jewel-toned goblets last for weeks. A single caveat before welcoming callas into your home: From their blooms to their roots, the plants are loaded with highly toxic calcium oxalate crystals. Display them where they won't endanger children or pets.
Starting the Callas
Growing Medium and Pots
Calla lilies need good drainage. Plant them in commercial, high-quality, peat-based potting mix and use deep pots with drainage holes. A 6-inch pot is large enough for one lily; an 8-inch one has room for two or three evenly spaced plants.
Plant the rhizomes, or bulbs, smooth side down in pots of pre-moistened potting mix at a depth at least twice their thickness. Water until liquid runs from the base of the container and let the pot drain completely.
Set the container in a spot with temperatures in the 60- to 85-degree Fahrenheit range and at least six hours of bright, indirect light each day. Water enough to keep the growing medium evenly moist while waiting for the rhizomes to sprout.
Water actively growing callas as needed to keep the growing medium moist without letting it become soggy. Excessive watering may cause stem and leaf yellowing from rotting rhizomes.
Before watering, test the medium a finger into its top 1 inch. If it's dry, water until fluid flows from the drainage holes, soaking the entire root system. Wait no more than one hour before emptying the water collection saucer.
From the time they sprout until they finish flowering, fertilize calla lilies every three weeks with a low-nitrogen, high-phosphorous liquid plant food. Look for one with the second of the N-P-K numbers on its label greater than the first, and apply it at one-half the label's recommended strength.
Replace a regular watering session with the fertilizer. Pour the solution evenly over the growing medium until it flows from the drainage holes.
Getting through Dormancy
When the callas stop blooming and their foliage becomes brown, they're entering a rest period called dormancy. Prune the leaves back to the medium and store the pots in a cool, dark dry location with a temperature between 32 and 50 F. After two to three months, start watering and gradually return the pots to warmer temperatures and brighter light. Resume a regular fertilizer schedule when the new leaves emerge.