The calla lily, scientifically known as Zantedeschia, is prized for its elegant, funnel-shaped spathe that wraps around a central spike. While these plants are relatively simple to cultivate, achieving a continuous, vibrant display of blooms throughout the growing season requires careful horticultural attention. The plant’s energy must be managed and redirected away from seed production and toward the development of new flower buds. Focusing on environmental factors, precise nutrient delivery, and timely maintenance practices will maximize the duration of the bloom period.
Establishing the Right Environment for Flowering
The foundation for prolific flowering begins with providing the correct balance of light and moisture. Calla lilies generally require full sun to partial shade, meaning they benefit from at least six hours of light daily. The intensity must be managed based on climate; in regions with intense summer heat, locating the plant where it receives bright morning sun and afternoon shade prevents scorching.
Consistent water availability is important, as Zantedeschia species are native to marshy areas and are heavy drinkers. The soil must be kept uniformly moist throughout the active growing period. Proper drainage is necessary to prevent waterlogged conditions that can lead to rhizome rot. Using a rich, well-draining potting mix ensures the plant receives sufficient moisture. Allowing the soil to dry out excessively can disrupt the flowering cycle and stress the plant.
Providing Consistent Nutrition for Reblooming
Sustaining the energy output required for continuous reblooming depends on a balanced nutritional program. Plants that receive too much nitrogen (the ‘N’ in NPK) will prioritize lush, green foliage growth at the expense of flower production. Therefore, the most effective fertilization strategy is to use a formula that is lower in nitrogen and higher in phosphorus and potassium.
A fertilizer with an NPK ratio such as 5-10-5, or a similar high-phosphorus formulation, encourages cell division and reproductive growth. This liquid fertilizer should be applied regularly during the active growing cycle, typically every two to four weeks. Fertilization should be discontinued once the plant shows signs of entering its natural dormancy period, preventing the encouragement of weak, late-season growth that drains energy reserves.
The Practice of Deadheading Spent Blooms
Deadheading, the removal of spent flowers, redirects the plant’s resources away from seed formation and back into producing new rhizome buds and flowers. When a calla lily flower fades, it begins the process of setting seed, which consumes stored energy. Prompt removal of the spent spathe signals the plant to focus its energy elsewhere.
The spent flower stem should be removed as close to the base of the plant as possible, using clean, sharp shears. Cutting the entire stem near the soil line, rather than just snipping the flower head, prevents the hollow stem from collecting water and potentially causing rot near the rhizome. This technique also minimizes the chance of leaving a decaying stub and encourages disease. Any yellowing or damaged foliage should also be gently removed to maintain plant health and appearance.
Managing the Post-Bloom Dormancy Period
To ensure the calla lily has the energy reserves necessary for a strong bloom cycle, a period of rest, or dormancy, is required. The plant signals the onset of this phase by allowing its foliage to yellow and die back, typically in late summer or early fall. This yellowing should be allowed to happen because the leaves are actively photosynthesizing and transferring energy back to the rhizome.
Once the foliage has completely died back, water intake should be significantly reduced and eventually stopped. For container plants, the pot can be moved to a cool, dark location, such as a basement or garage, where temperatures remain above freezing (ideally between 40 and 50 degrees Fahrenheit). In colder climates (below USDA Zone 8), in-ground rhizomes must be lifted, dried, and stored in peat moss or sawdust until the danger of frost has passed the following spring. This forced rest period, lasting a minimum of two to three months, is essential for the rhizome to recharge and prepare for abundant flowering.