Calla lilies (Zantedeschia aethiopica) are tropical plants that have showy flowers in shades of pink, yellow, red, orange, and white. Most varieties also have mottled or marked foliage that is attractive even when the plant is not in bloom. Callas prefer a slightly shady location but will grow in full sun if it's not too hot. Their blooms are relatively long-lasting but usually finish up by mid-July. You can purchase calla lily rhizomes in spring at garden centers and nurseries. Plant the rhizomes in spring in pots or directly in the garden in soil amended with well-rotted compost, manure, or sphagnum peat moss. The plants are sensitive to frost, so wait to plant them until all frost danger is past. The rhizomes should be planted 4 inches deep. Calla lilies will overwinter outdoors in Zones 9-11, but in most places they need to overwinter indoors. If you've grown the plants in pots, you can simply move the pots inside to a dark location for the winter without having to dig at all. Just repot them in fresh soil in spring. If you've planted them in the garden, dig up the rhizomes at the end of the growing season. Store them in a cool, dry location until next spring.