Calla lilies (Zantedeschia) are cultivated for their elegant, trumpet-shaped blooms and striking foliage. Harvesting involves two distinct methods: cutting the decorative flower (a modified leaf called a spathe) for floral arrangements, or digging up the underground storage structures (rhizomes) to protect them from cold winter temperatures.
Cutting Blooms for Floral Arrangements
The longevity of a cut calla lily bloom depends on the timing of the harvest. The optimal time to cut the flower is early morning when the plant is fully hydrated and the spathe has partially or fully unfurled. Use a sharp, sterilized blade to make a clean incision, as crushed stems impede water uptake and shorten vase life.
Cut the stem at a sharp 45-degree angle near the base of the plant to maximize the surface area for water absorption. Alternatively, some varieties can be twisted or pulled gently at the base to separate them cleanly from the rhizome. Immediately place the stems into a shallow container of lukewarm water to prevent air bubbles from forming, which block hydration uptake.
Calla lily stems are mostly water and can deteriorate if fully submerged, so use only one to two inches of water in the final vase. Trimming the stems and changing the water every two days prevents bacterial growth, a common cause of premature wilting. Adding commercial flower food or a solution of sugar, lemon juice, and bleach provides nutrients and acts as a biocide to keep the water clean.
Preparing Rhizomes for Winter Dormancy
In regions where winter temperatures drop below freezing (USDA Hardiness Zones 7 and lower), tender rhizomes must be lifted for protection. Begin this process in the fall, waiting until the foliage has naturally yellowed and begun to die back, or after the first light frost. This waiting period ensures the plant has transferred maximum energy and nutrients back into the rhizome for winter survival.
Use a spade to carefully lift the plant, maintaining a wide margin around the visible stems to avoid injuring the underground rhizome. Damage creates an entry point for pathogens like bacterial soft rot during storage. Gently brush off excess dirt once the plant is out of the soil, but do not wash the rhizomes, as excess moisture encourages rot.
Trim the remaining foliage, leaving only a short stub of one to three inches attached to the rhizome. The integrity of this stored tissue is crucial for the plant’s health the following season. Before curing, cut away any soft, diseased, or mushy areas using a clean, sterile knife.
Post-Harvest Storage of Rhizomes
After cleaning, the rhizomes must undergo curing, a hardening period that toughens the outer skin. Curing requires a protected, warm, and well-ventilated location, ideally between 60 and 70°F. Spread the rhizomes in a single layer on a tray or cardboard for seven to ten days until the surfaces feel dry and firm.
Once cured, the rhizomes are ready for long-term dormant storage in a cool, dry environment. Maintain the storage temperature consistently between 40 and 60°F; 50°F is optimal to prevent chilling injury or premature sprouting. A garage, basement, or unheated closet can provide the necessary conditions, provided temperatures remain above freezing.
Nest the rhizomes in a dry storage medium such as peat moss, vermiculite, or sawdust, and use a container that allows for air circulation, like a vented cardboard box or paper bag. This medium regulates humidity and keeps the rhizomes from touching, reducing the risk of disease spread. Check the rhizomes periodically throughout the winter to ensure they are not shriveling from dryness or developing mold from excess moisture.