Calla lilies are the quintessential bouquet flower. They have graced vases on a thousand tables and been presented in untold bouquets. It's easy to see why; with such graceful and elegant flowers, they are easy to love. As with any plant in such high demand, there are many varieties of the basic plant. They've been bred for size and shape, even color. They are, and they grow like typical aroids. They like dappled sunlight or even light shade, along with high temperatures, high humidity, lots of fertilizer, and ample water during the growing season, followed by a cooler and drier dormant period during the late fall and early winter.
If you have a glasshouse, or better yet, a hydroponics set-up, you can grow beautiful calla lilies. Even if you don't, though, you can keep the plants going for at least one growing season.
Light: Bright, indirect light during the growing season. They dislike direct sunlight.
Water: Keep potted and blooming plants constantly moist. As the blooms fall, reduce watering until all the flowers are gone; then let the leaves wither and die as the plant dries out. Give it a brief resting period, then repot in late winter into fresh soil and begin watering again to encourage new sprouts.
Temperature: On the warm side (up to 80˚F) during growth and blooming. During the dormant period, cooler if possible (down to 50˚F).
Soil: A loose, well-drained potting mix.
Fertilizer: Fertilize during the growing season with liquid fertilizer or controlled-release fertilizer according to label instructions.
Stop fertilizer during dormancy.
Callas can be propagated from the old rhizomes by division. Outside, over time plants will form large clumps that can be easily divided into smaller units. However, callas are only viable outside in USDA zones 10 or 11, so most people growing callas will be growing pot-bound specimens.
Unfortunately, while rhizome division is still possible with indoor specimens, over time the plants will begin to lose vigor, and their flowers will never regain their original strength. So unless you're very attached to propagation, it's probably a good idea to discard expended plants and buy new ones.
Repotting should be done in the mid-winter after the plant has gone into its dormant phase and rested in a cool place in its spent soil. To repot, remove the rhizome from the old pot and place into the fresh soil (smooth side down) in a slightly larger pot. Begin watering immediately to encourage new growth.
The basic calla lily is a Zantedeschia hybrid. The most common plants feature a yellow spadix surrounded by a white spathe. Recent breeding efforts, however, have introduced flowers with deep red spathes, or even mixed or speckled specimens. The typical calla lily will grow to a height of 36" outdoors, but shorter hybrids have been produced with Z. rehmanii that stay about 12 inches tall and are perfect for desktops.
Calla lilies are such beautiful plants; it's hard not to splurge on one occasionally. While they are growing and blooming, keep them adequately fertilized and watered, misting the plant every so often to keep the ambient humidity high.
Plants that are exposed to direct sunlight will develop damaged flowers, so watch out for leaf tip burn or discolorations. They are also susceptible to aphids. If you want to keep your plant after the bloom is finished, snip off the flowers and the fading leaves, only slowly reducing water, until the plant totally fails. Although it can be fun to rejuvenate a plant from the rhizome, it will never achieve the same bloom, so it might be wiser to think of calla lilies like gift phalaenopsis orchids: somewhat disposable after the bloom is finished.