Calla lilies (Zantedeschia spp.) are well-suited to grow in Florida's warm climate, but the soil probably needs to be amended before they are planted. Several varieties of calla lilies are available, and they have very similar requirements.
U.S. Department of Agriculture plant hardiness zones 8 through 11a cover Florida, and USDA zones 8 through 11 are where white calla lily (Zantedeschia aethiopica), pink calla lily (Zantedeschia rehmannii) and several calla lily cultivars can survive year round in the ground, growing as perennials. Some cultivars, however, grow as perennials in the ground in only USDA zones 9 through 11. They include 'Crystal Blush' calla lily (Zantedeschia 'Crystal Blush') and 'Sunshine' calla lily (Zantedeschia 'Sunshine'). Check a cultivar's USDA zones before planting it in northern Florida.
Most kinds of soil in Florida are sandy, which is not the best choice when growing calla lilies. Unlike most bulb plants, which prefer well-drained soil, calla lilies grow best in moist soil rich in organic matter. They even grow in standing water along the banks of rivers and ponds.
To get around a sandy soil problem, many Florida gardeners grow calla lilies in pots set in trays of water to keep the soil moist. If, though, you want to grow calla lilies in the ground, then add organic matter to the soil before planting. Sphagnum peat, well-rotted compost and aged manure are additives that help sandy soil hold water. Apply a 2- to 3-inch layer of any of those organic amendments on the soil surface where you want to plant calla lilies, and then break up and mix the layer into the soil to a depth of 6 to 8 inches.
If you live in a part of northern or central Florida that has clay-based soil, then mix a 2- to 3-inch layer of peat moss and either shredded tree bark or chipped wood with the soil to a 6- to 8-inch depth. Those amendments loosen the soil while providing the organic matter that calla lilies need.
In parts of central and southern Florida with peat-based soil, amending the soil may not be necessary.
Calla lilies need plenty of sunlight to flower, but they also need shade during the hottest parts of the day in Florida's warm climates. A location with bright morning sunlight and filtered shade in the afternoon is ideal for giving the plants enough light while protecting them from drying out too much. The more light you can supply while still keeping the soil moist, the better.
Plant calla lily rhizomes 4 inches deep and 1 to 2 feet apart in the garden in spring or fall while the rhizomes are dormant. Most varieties do best when planted in spring.
Providing Ongoing Care
To keep calla lilies healthy in Florida's hot summers, supply them with plenty of water. Water often enough to keep their soil moist while the plants are green and growing. Calla lilies need a resting period in order to set blooms for next year, even in locations where the growing season extends year round, as it does along Florida's southern coasts.
After calla lilies flower, watch their foliage carefully so you will know when to let the plants go dormant. The foliage will stay green and glossy for some time after the flowering then start to decline as the plants become dormant in fall. Gradually reduce their watering during that decline, and stop watering when the foliage dies. Leave the calla lilies alone for two to three months, and then begin watering them again in early spring as they come out of dormancy.
Fertilize calla lilies when they are actively growing or in bloom. They do not require fertilizer from the time they start to go dormant until their new leaves appear in spring. Use a water-soluble, all-purpose plant food with a nitrogen-phosphorus-potassium ratio of 24-8-16, diluted by mixing 1 tablespoon of it with 1 gallon of water. One gallon of the diluted fertilizer will feed 10 square feet of plants in the garden. Reapply the diluted fertilizer solution every two to four weeks, in place of a regular watering.