What you must do to keep your calla lilies safe through the winter months depends on where you live. In tropical locations or in USDA zones 8 to 10, calla lilies will thrive outdoors throughout the year and can be planted at any time. Some gardeners in these warmer climates prefer to mulch their bulbs with bark or straw during the coldest months of the year. In less temperate climates, there are required precautions necessary to protect your calla lilies.
If your calla lily is potted, bring the plant indoors and let it remain in the pot throughout the winter. Do not water the plant until you want growth to begin in the spring. You can start your calla Lilies indoors in the spring. Ensure that the pots are placed in full sun and that when you plant the bulbs their tips are just below the soil level. When replanting your calla lilies in the spring, choose a location that gets bright, morning light. Calla lily bulbs need to be planted deeper than many other bulbs. When replanting the bulb, also known as a rhizome, the bulb should be placed four inches into the soil and 12 inches from the next nearest bulb.
The coolest temperature at which a calla lily can survive is 50 to 55 degrees.