The Calla Lily, a plant from the Zantedeschia genus, offers a tropical aesthetic to any garden setting. Originating in South Africa, these perennials are recognized for their dramatic, trumpet-shaped blooms, which are technically modified leaves called spathes. While often grown as houseplants, the Calla Lily thrives outdoors in flower beds and containers. Successful cultivation requires understanding their specific needs, particularly concerning their rhizomatous structure and preference for moisture.
Initial Site Preparation and Planting
Selecting the proper location is primary to the plant’s health and blooming capacity. Calla Lilies perform best with full morning sunlight, but require afternoon shade in intense heat to prevent leaf scorch. While they love moisture, they are extremely prone to rot in waterlogged conditions, making soil structure critical.
The planting medium should be rich and well-draining, ideally amended with organic matter like compost or well-rotted manure. This enhances fertility while ensuring excess water moves away from the rhizomes. Plant Calla Lilies outdoors only after the last risk of frost has passed in the spring, allowing the soil to warm sufficiently.
The rhizomes should be buried approximately 2 to 4 inches deep, with the growing points or “eyes” facing upward. Space them 12 to 18 inches apart in garden beds to allow for airflow and mature growth. After planting, initial watering should be light until the first signs of green foliage emerge, signaling active growth.
Essential Ongoing Care During the Growing Season
Calla Lilies require consistently moist soil conditions during their active growth phase. Keep the soil evenly moist but never completely saturated to prevent root diseases. Allowing the top inch of soil to dry slightly between watering sessions helps maintain this balance.
These plants are heavy feeders and benefit significantly from regular nutrient supplementation. Apply a balanced, water-soluble fertilizer every four to six weeks to support vigorous growth and blooming. Alternatively, a slow-release granular fertilizer can be incorporated into the soil at planting time. Once growth is established, a lower nitrogen content is preferred, as excessive nitrogen encourages foliage growth at the expense of flowers.
Regular maintenance pruning, known as deadheading, encourages a longer bloom period. Remove spent flowers by cutting the stem back to the plant’s base, redirecting energy toward new blooms instead of seeds. Damaged or yellowing leaves should also be removed to improve the plant’s appearance and health.
The most common issue affecting Zantedeschia is bacterial soft rot, which results in soft, slimy rhizomes and plant collapse. This condition is favored by overly wet or poorly drained soil, emphasizing the need for proper site selection and irrigation. Other potential pests include aphids, which may be found on developing flower stalks and leaves.
Seasonal Transition and Overwintering
As the outdoor temperature drops in the fall, the Calla Lily’s foliage will yellow and die back. This transition allows the rhizome to store necessary nutrients for the following year’s growth cycle.
In warmer regions (USDA Hardiness Zones 8 and higher), the rhizomes can remain in the ground over winter. Gardeners should cease watering and cover the planting site with a thick layer of mulch for insulation. In colder climates (Zone 7 and below), the rhizomes must be lifted to prevent freezing.
Lifting should occur after the first light frost has killed the foliage, ensuring nutrients have fully returned to the rhizome. After digging, allow the rhizomes to dry or “cure” in a warm, dry area for about one to two weeks. Once cured, store the rhizomes in a cool, dark, and frost-free location where the temperature remains between 40 and 60 degrees Fahrenheit.