Purple calla lilies thrive in wet soils in USDA Hardiness Zones 8 to 10 throughout the southern United States, including parts of North Carolina, South Carolina, Georgia, Arkansas, Alabama, Mississippi, Texas and Louisiana. Here, their season is considered to be year round. But in colder northern climes, calla lilies can be planted in the garden in the spring. However, they cannot tolerate temperatures under 30 degrees Fahrenheit. They can also be planted in containers and moved inside before the first frost.
While all calla lilies bloom in the late spring and early summer, some will also flower again in the fall. The showy, furled blooms can last for up to a month. Leave the foliage in place after blooming for the season. Yellowed leaves can be removed.
Calla lilies grow from potato-like rhizomes. Plant in full sun to partial shade about an inch deep. They grow best in moist soil and can be planted at the edge of ponds to take advantage of the wet soil. Their season can be extended in colder areas by planting the rhizomes in containers inside before moving them to the garden in warmer weather.
The season for purple varieties is the same as for other colors. While white calla lilies are most common, several exotic shades of hybrid purple calla lilies add drama to the garden. The deep purple Anneke has a brilliant yellow interior, while the Captain Chelsea variety is yellow on the exterior lined with a rich burgundy-purple color. The purple hue of the Edge of Night calla lily extends all the way to the stem and its purple-edged leaves.