Calla lilies (Zantedeschia) are admired for their elegant, trumpet-shaped blooms. These tender perennial rhizomes, often mistakenly called bulbs, originate from warmer regions of Africa. In climates with freezing winter temperatures, the rhizomes will not survive the cold ground. Lifting and storing them indoors protects them from frost, ensuring survival and successful reblooming after a necessary dormancy period.
Preparing the Bulbs for Dormancy
The transition process begins in autumn after the flowering season ends. Wait until the first light frost naturally kills the foliage, which signals dormancy and ensures maximum nutrient storage in the rhizome. Alternatively, cease watering the plants in mid-fall to induce the foliage to yellow and die back.
Once the leaves have yellowed or been frosted, trim the foliage back, leaving a stub of about two to four inches above the soil line. Carefully lift the rhizomes from the ground using a garden fork to avoid damaging the fleshy structure. Gently shake off any excess soil, but do not wash them, as added moisture significantly increases the risk of rot during storage.
The next step is the curing process, which toughens the outer skin of the rhizome for protection. Place the cleaned rhizomes in a single layer on a tray in a protected, well-ventilated location out of direct sunlight. The ideal temperature for curing is between 60°F and 70°F (15°C to 21°C). Continue this air-drying for approximately seven to ten days until the exterior feels dry and slightly hardened.
Establishing Ideal Storage Conditions
After curing, move the rhizomes to an environment that maintains cool, dry, and consistent conditions throughout the winter. The storage container must allow for adequate air circulation to prevent moisture buildup, the primary cause of fungal rot. Cardboard boxes, paper bags, or mesh sacks are excellent choices, but avoid plastic bags or sealed containers.
To regulate moisture and prevent the rhizomes from touching, layer them with a dry, inert medium. This packing medium helps maintain a stable environment and isolates any potential infection. Suitable materials include:
- Dry peat moss.
- Vermiculite.
- Sawdust.
- Dry shredded newspaper.
The storage location must be dark, dry, and consistently cool, with an ideal temperature range of 50°F to 55°F (10°C to 13°C). The area must never drop below 45°F (7°C), as freezing will destroy the rhizomes. A cool, dry basement or an unheated garage that remains above freezing can serve as an appropriate location, provided the humidity is low, ideally below 55%.
Monitoring and Reawakening the Bulbs
Periodic checks of the stored rhizomes are necessary throughout the dormancy period, ideally on a monthly basis. Inspect the rhizomes for any signs of decay, such as mold growth, soft spots, or a mushy texture. Immediately discard any affected rhizomes to prevent the spread of pathogens to healthy stock.
It is also important to ensure the rhizomes do not completely desiccate, which can cause them to shrivel and wrinkle. If they appear shrunken or overly dry, lightly mist the surrounding storage medium with water to restore minimal moisture. The goal is to maintain minimal residual moisture to sustain cell integrity without promoting rot.
The reawakening process should begin approximately four to six weeks before the last expected spring frost in your region. Move the rhizomes to a warmer location to encourage them to break dormancy and begin sprouting. This head start allows the plant to establish roots and foliage indoors before the outdoor planting date. The rhizomes should be firm to the touch before potting, which indicates they are healthy and ready for the next growing season.