Calla Lilies (Zantedeschia) are admired for their elegant, trumpet-shaped flowers, which are actually modified leaves called spathes surrounding a central spike called a spadix. These striking plants are seasonal bloomers, producing a primary flush of flowers during their active growing season, typically spanning late spring into summer. Unlike some perennials that bloom continuously until frost, a Calla Lily’s flowering is finite, tied directly to the energy stored in its underground structure. While a true, robust “rebloom” is uncommon, gardeners can encourage secondary flower production within the same season and ensure a reliable return of flowers in subsequent years.
The Calla Lily’s Natural Flowering Pattern
The flowering cycle of the Calla Lily is fundamentally determined by its species and the type of underground storage organ it possesses. The classic white variety, Zantedeschia aethiopica, grows from a rhizome and is often semi-evergreen in mild climates, preferring consistently moist to boggy soil. This type tends to have a longer, sometimes more sporadic, bloom period that can extend from late winter through summer in warm regions.
In contrast, the brightly colored hybrids—ranging from yellow to deep purple—grow from deciduous tubers and originate from drier regions of South Africa. These colored varieties are strictly seasonal, entering a full dormancy period where their foliage dies back completely. Their flowering is a concentrated effort, typically occurring from late spring into mid-summer. The initial, most numerous, and largest flowers of any Calla Lily are produced when the stored carbohydrates in the rhizome or tuber are at their maximum, making the first flush the most spectacular.
Stimulating Additional Blooms Within the Growing Season
Encouraging a second round of flowers during the current season requires redirecting the plant’s energy away from seed production. The process of removing spent flowers, known as deadheading, is the most direct way to achieve this goal. Once a flower spathe begins to fade, it signals the plant to shift its resources into forming seeds within the central spadix.
To interrupt this process, the entire flower stem should be removed at its base, down near the foliage, before the spathe fully withers. Making this cut cleanly prevents the formation of a hollow stub that could collect water and lead to rot. This action forces the plant to conserve the energy it would have spent on reproduction and channels it toward developing new growth points, which may include secondary flower buds.
Supplemental feeding mid-season can further support this effort, as the plant’s initial energy reserves are depleted after the first bloom. Apply a liquid fertilizer that is low in nitrogen but high in phosphorus and potassium, as this nutrient ratio specifically promotes flower development over leafy growth. Maintaining even, consistent moisture is also imperative, as the colored, tuberous varieties will prematurely cease flowering and enter dormancy if they experience significant drought stress.
Managing Dormancy for Next Year’s Flowers
A successful rebloom in the next growing cycle depends on giving the Calla Lily a proper, enforced rest period. As the season concludes and temperatures cool, the plant prepares for dormancy by drawing energy from its foliage back into its underground storage structure. Gradually reduce watering and stop fertilization completely once the leaves begin to yellow, allowing the foliage to die back naturally.
For the hardy white Calla Lily, Z. aethiopica, robust in USDA Zones 8–10, the rhizomes can remain in the ground over winter. Once the foliage is fully withered, cut it back to soil level. The plant bed may benefit from a layer of protective organic mulch in the coldest part of its range. The more tender, colored, tuberous hybrids, however, must be lifted in climates with freezing winters.
Before the first hard frost, dig up the tubers, gently clean off excess soil, and allow them to air-dry in a cool, shaded area for two to three days. This curing process helps seal any wounds and prevents fungal diseases during storage. Store the dried tubers in a cool, dark location, such as a basement or garage, where the temperature remains consistently between 50°F and 60°F. Storing them in a breathable material like dry peat moss or wood shavings prevents desiccation while ensuring adequate air circulation. Once spring arrives and the soil temperature reaches at least 65°F, the tubers can be replanted to initiate the next cycle of vegetative growth and, ultimately, a fresh display of flowers.