Calla lilies, from the Zantedischia species, grow from bulbs that last for many years. The foliage and flowers are short lived, but continued production from the bulbs classifies these plants as perennials. Callas are not hardy as plants or bulbs, though, and require the right care to maintain their growth and blooming habits.
Callas emerge from the soil in spring, but may not bloom until midsummer. Size, color and blooming time depends on cultivar and the year’s weather. Callas bear foliage and blooms through summer, but yellow and die down to the ground in fall for their winter dormancy.
Calla lilies can grow in partial shade but produce better flowers — and more of them — when they grow in full sunshine. Find sites that drain quickly for all colors of calla but white, as white callas will grow in boggy soil. Give each calla lily bulb 1 to 2 feet of space for growing and multiplying.
Callas need deep, loose and nutritious soil to give them room and resources for root expansion. Mix 5 inches of organic compost into the top 10 inches of soil in each planting site and plant call bulbs 4 to 6 inches deep, with pointed ends up.
Maintain calla bulbs and plants with 2 inches of water a week through summer, until they die back. Gardeners in U.S. Department of Agriculture Growing Zone 9 and up can leave calla bulbs in the ground through winter, but the bulbs will freeze in colder areas. Gardeners in USDA Zones 8 and under should dig the bulbs after they go dormant and replant them in boxes of soil for the winter, for outdoor planting again in spring.