The Calla Lily, a plant belonging to the genus Zantedeschia, is not a true lily but an elegant, rhizomatous perennial native to southern Africa. It is widely prized for its distinctive, trumpet-shaped blooms, which are botanically a spathe surrounding a central spadix. These flowers are popular in both garden beds as ornamental plants and in the floral industry as a sophisticated cut flower. The timing and duration of its display are not fixed but are highly dependent on whether it is grown outdoors, in a container, or forced indoors by manipulating its environment.
The Natural Blooming Season
For calla lilies planted outdoors in spring after the danger of frost has passed, the standard blooming window begins in late spring and continues through mid-summer. The rhizomes typically take about two to three months after planting to produce their first flowers, with the peak display occurring during the warmer months. The overall flowering period for a healthy, established plant generally lasts between six and twelve weeks, depending on the specific variety and local climate conditions.
Individual blooms are long-lasting, remaining vibrant on the plant for several weeks and lasting up to two weeks when harvested as cut flowers. Two primary groups of Zantedeschia are commonly grown: the large, white-flowered Z. aethiopica and the colorful hybrid varieties (pink, yellow, orange, near-black). The colorful hybrids are often treated as annuals in colder regions, while Z. aethiopica is more robust and may perennialize in milder climates.
Environmental Triggers for Flower Production
The initiation of flowering in calla lilies is a direct response to specific environmental cues. To encourage the formation of flower buds, plants require adequate light, with bright, indirect sun ideal, though full sun is tolerated in cooler climates. If planted in hot regions, the plant benefits from some afternoon shade to prevent scorching and maintain vigor.
Temperature plays a significant role, as calla lilies thrive in stable warmth, preferring temperatures between 60°F and 80°F. Soil must be consistently moist and rich in organic matter, as dry conditions can inhibit bloom production. For container plants and those grown in cooler climates, blooming can be “forced” outside the natural summer cycle by providing a bright, warm location and ensuring the rhizome has completed its rest period.
Many colored hybrid varieties require a distinct period of dormancy to store energy and set buds. Without this rest, the plant will often produce lush foliage but fail to initiate new flower spikes. Growers can manipulate this cycle by withholding water and light to simulate the natural dry season, allowing commercial production for holidays like Easter, well before the normal outdoor season.
Managing Post-Bloom Care and Dormancy
Once the calla lily’s bloom begins to fade, care is required to ensure the plant can successfully flower again. Removing the spent flower stalk, a process called deadheading, should be done by gently pulling the entire stem from the base of the plant. This prevents the plant from diverting energy into seed production, encouraging it to put resources back into the rhizome.
As the growing season concludes and temperatures drop below 50°F, the plant enters dormancy. The foliage will begin to yellow and die back. At this point, watering should be significantly reduced or stopped entirely to allow the plant to dry out.
For gardeners in zones colder than USDA Hardiness Zone 8, the rhizomes must be lifted from the ground before the first hard frost. After cutting the yellowed foliage back to a couple of inches, allow the rhizomes to cure in a warm, dry, well-ventilated area for several days. Store the cured rhizomes in a cool, dark, and frost-free location (ideally 40°F to 50°F) for a rest period of two to three months before replanting the following spring.