The Calla Lily is a popular plant recognized for its elegant, trumpet-shaped blooms and glossy foliage. This plant grows from an underground stem called a rhizome and is frequently purchased as a potted houseplant. Moving a Calla Lily outdoors is a common goal for gardeners seeking more robust growth and a greater abundance of flowers than are typically achieved indoors. The success of this transition depends on careful preparation, correct planting technique, and managing the plant’s seasonal needs.
Determining If Your Climate Allows Outdoor Planting
The decision to plant a Calla Lily permanently outside rests on winter temperatures. Calla Lilies are tender perennials and are generally only hardy enough to survive year-round in USDA Hardiness Zones 8 through 10. The plant’s rhizome will suffer damage or rot in freezing conditions, and a hard frost is typically fatal.
The classic white variety is often more resilient and can sometimes survive in Zone 7 with heavy protection. Brightly colored hybrids, such as yellow, pink, and burgundy varieties, are less cold-tolerant and must be lifted for winter storage in Zone 7 and colder regions. Regardless of the variety, planting should be delayed until the soil temperature is consistently 60 to 65°F.
Preparing the Calla Lily for Transplanting
A potted Calla Lily must be gradually acclimated to the harsher outdoor conditions. This process, known as “hardening off,” involves slowly exposing the plant to wind, direct sun, and temperature fluctuations over seven to ten days. Begin by placing the pot in a sheltered, shady location for a few hours each day, returning it indoors at night.
Incrementally increase the amount of sunlight and time spent outdoors, protecting the plant from intense midday sun and strong winds. The ideal outdoor location should receive full sun in cooler climates. In hot summer regions, a spot with morning sun and afternoon shade is preferred to prevent leaf scorching. The final planting site must also have excellent drainage, as the rhizomes are prone to rotting in soggy soil.
Step-by-Step Guide to Planting Outdoors
Once the plant is hardened off and the danger of frost has passed, begin the transplanting process. Prepare the planting hole by digging it approximately twice as wide as the current root ball but no deeper. Loosen the soil at the bottom of the hole and mix in organic matter, such as well-rotted compost, to provide nutrients and improve soil texture.
Carefully remove the Calla Lily from its pot, minimizing disturbance to the root system, and gently place it into the prepared hole. The top of the root ball should be level with the surrounding garden soil. If planting a bare rhizome, place it three to four inches deep with the growing points, or “eyes,” facing upward. Backfill the hole with the amended soil, lightly firming it around the plant, and water thoroughly to settle the soil and eliminate air pockets.
Seasonal Care and Winter Survival
Throughout the active summer growing season, the outdoor Calla Lily requires consistently moist soil to thrive, but avoid waterlogged conditions that promote rot. Applying mulch around the base of the plant helps regulate soil temperature, suppress weeds, and maintain moisture levels. During active growth and flowering, the plant benefits from a slow-release granular fertilizer applied at planting, or a liquid feed every few weeks.
In the autumn, the plant naturally enters dormancy, signaled by the yellowing and dying back of the foliage.
Winter Survival in Warm Zones
If you are in Hardiness Zones 8 through 10, stop watering and cut the dead foliage back to the ground. The rhizome can remain in the soil, often protected by a thick layer of insulating mulch.
Winter Survival in Cold Zones
Gardeners in Zone 7 and colder must dig up the rhizomes before the first hard frost. The lifted rhizomes should be cured in a warm, dry location for several days to toughen the outer skin. Store them indoors at about 50°F in a material like peat moss or sawdust until they can be replanted the following spring.