The Calla Lily (Zantedeschia) is known for its elegant, trumpet-shaped flowers and glossy foliage, making it a popular choice for gardens and cut-flower arrangements. Originating from South Africa, the plant enjoys warm, moist conditions year-round. Whether the Calla Lily reliably returns each spring depends almost entirely on the local environment. Gardeners must understand the plant’s biology and sensitivity to cold temperatures to ensure its return.
The Calla Lily’s Perennial Status
Calla Lilies are classified as tender perennials, meaning they can live for multiple years under the right conditions. The plant grows from an underground storage structure called a rhizome, which stores the energy needed for the next season’s growth. This rhizome must survive the winter months intact for the plant to reappear in the spring.
The ability of the rhizome to survive outdoors is tied to the severity of the winter climate. In warmer regions (USDA Hardiness Zones 8 through 10), the soil does not freeze deeply enough to harm the rhizomes. Here, the Calla Lily naturally enters a period of semi-dormancy and is a reliable perennial that returns without special intervention.
In colder climates (Zone 7 and below), gardeners must treat the Calla Lily as a summer annual if they leave the rhizomes in the ground. The cold soil temperatures in these regions are lethal to the rhizomes. To achieve perennial status, gardeners must manually lift the underground structures and store them indoors, mimicking a warmer, dry winter environment.
Ensuring Return in Outdoor Gardens
For gardeners in Zones 8 to 10, ensuring the Calla Lily returns involves managing its natural dormancy. As the season cools, allow plants to die back naturally, signaling the plant to store energy in the rhizome. Once the foliage has yellowed and collapsed, cut it back to ground level. A light layer of mulch can then be applied for insulation and moisture retention.
For those in colder areas (Zone 7 and below), the process requires active winterizing to preserve the rhizomes. The optimal time to lift them is shortly after the first light frost causes the foliage to die back, ensuring maximum nutrient storage. After carefully digging up the rhizomes, gently brush off the excess soil. Avoid washing them, as moisture can promote rot.
Curing and Storage
The next step is curing, where the rhizomes dry in a warm, dark, well-ventilated area for several days to a week. Curing toughens the outer skin, making the structures less susceptible to disease during storage. Once cured, the rhizomes should be stored in a breathable medium. Use materials like peat moss, vermiculite, or dry shredded paper, placed in a paper bag or vented cardboard box.
The storage location must be kept cool, dark, and dry, ideally maintaining a consistent temperature between 50 and 60 degrees Fahrenheit. This range keeps the rhizomes dormant but prevents freezing and damage. In the spring, once the danger of the last frost has passed and the soil temperature has warmed to at least 65°F, the rhizomes can be replanted.
Managing Potted Calla Lilies
Growing Calla Lilies in containers allows gardeners in any climate to easily manage the plant’s dormancy and ensure its return. Overwintering potted plants requires managing the shift into dormancy by controlling the water supply. As the growing season ends, usually in mid-to-late fall, gradually stop watering the pot entirely.
Withholding water forces the plant into its resting phase; the foliage will yellow and collapse as stored energy moves into the rhizome. Once the leaves are dead, trim them back to the soil line. The entire pot, with the rhizome safely inside the soil, can then be moved to a cool, dark, and dry location for the winter.
The optimal storage temperature for the potted rhizome is between 40 and 50 degrees Fahrenheit. The benefit of this method is that the rhizome remains undisturbed in its soil, simplifying the process. Alternatively, some gardeners treat the plant as a temporary houseplant, bringing it indoors before frost and placing it in a bright location to keep it actively growing.