Calla lilies are also known as zantedeschia, arum lilies, trumpet lilies or pig lilies. Whatever they are called, these plants are a beautiful addition to gardens. The plant can grow upwards to 39 inches tall, with dark green arrow-shaped leaves and cup-like flowers that come in a variety of colors. Whether you lift the calla lily rhizome each fall to transplant or leave it in the ground depends upon where you live.
Calla lilies are not cold hardy. According to Pacific Callas, in USDA Hardiness Zones 9 and 10 they can be left in the ground during the winter, although they claim to have customers in Zone 7 and below that have successfully left them in the ground over the winter. In all other zones, the rhizomes need to be dug up and stored for the winter.
In the fall, after the first frost, dig up the calla lily’s rhizome. Remove any soil and place them in a warm, sunny window to dry for several days. Store them in a dark, well-ventilated location that stays between 50 and 60 degrees throughout the winter.
In the spring, after all danger of frost has passed, transplant the calla lilies. They like full sun to light shade, but need to be protected from strong winds. They thrive in moist, humus-rich soil that is free-draining. Plant the rhizomes 4 inches deep and 12 to 18 inches apart. Water calla lilies regularly to keep them moist but not soggy–especially during the blooming season. When they begin to bloom, apply liquid fertilizer every three to four weeks.
Calla lilies do not need to be dug up and transplanted in warmer climates. they can be left in the ground throughout the winter as other perennials are. Plant them after the last frost in spring. Watering and feeding calla lilies is the same in warm climates as it is in cooler climates. Remove spent flowers as they fade.
In the fall, cover the calla lilies with a layer of dry leaves to protect them for winter. In some areas, they will die back completely; insert a plant marker nearby to prevent accidentally disturbing them in the spring.
Calla lilies can be divided in the fall, when the rhizomes are lifted. Look for little buds forming on the top and edge of the rhizome. The larger buds that break off easily are ready for dividing. Once divided, the cut "wound" needs to dry and heal in a warm, sunny spot before being stored for the winter.
Parts of calla lilies are toxic and should be planted and stored where children and pets cannot reach them