From a botanical perspective, not all Calla Lily (Zantedeschia spp.) cultivars are equally suited for cutting. The primary considerations are the genetic potential for long, strong flower stalks (scapes) and a long post-harvest vase life. Modern hybrid cultivars, particularly those derived from Zantedeschia aethiopica and the colorful Zantedeschia hybrids, have been selectively bred for these traits. For optimal bouquet use, select varieties known for their robust stems that can support the weight of the flower head (the spathe). Taller cultivars, which can produce stems over 24 inches, are ideal. Furthermore, some cultivars have been bred for thicker cell walls and more efficient vascular systems, which contribute to better water uptake and longevity after cutting.
The structural integrity of the cut flower stem is paramount. To cultivate plants that produce thick, sturdy scapes, the growing conditions must be optimized. Calla Lilies require full sun to partial shade. From a plant physiology standpoint, ample sunlight is crucial for photosynthesis, producing the carbohydrates necessary for building strong cellular structures. However, in very hot climates, intense afternoon sun can cause stress, leading to shorter stems; therefore, light afternoon shade can be beneficial. The soil must be consistently moist but exceptionally well-draining. Waterlogged conditions can lead to rhizome or root rot, severely weakening the entire plant and its flower stems. Rich, slightly acidic to neutral soil amended with organic matter will provide a steady supply of nutrients for sustained growth.
A Calla Lily's ability to produce multiple, high-quality flowers for cutting is directly linked to its nutritional status. These plants are moderate to heavy feeders. A balanced, water-soluble fertilizer with a formulation higher in phosphorus (the middle number in N-P-K, e.g., 5-10-5) is recommended once growth emerges. Phosphorus is vital for promoting robust root development and prolific flowering. However, it is critical to avoid excessive nitrogen. While nitrogen encourages lush leaf growth, an imbalance can direct the plant's energy away from flower production and result in weaker, softer stems that are prone to bending. Consistent feeding every two to three weeks during the active growing season supports the plant's metabolic demands for continuous flower production.
The act of harvesting is a physiological shock to the plant. To ensure the cut flower has the longest possible vase life, the timing and technique are scientific. The optimal time to harvest is in the cool of the morning or late evening when the plant's carbohydrate reserves are highest. The flower should be cut when the spathe has fully unfurled and is firm to the touch, showing its complete color. Cutting too early, when the spathe is still tight, may prevent it from opening fully. Using a sharp, sterilized knife or pruners, make a clean, angled cut at the base of the stem. The angled cut increases the surface area for water uptake. Immediately after cutting, the stems should be placed in a bucket of clean, lukewarm water. It is critical to avoid introducing air into the vascular system (xylem), which can form an embolism and block water flow.
Once harvested, the flower's lifespan depends on managing its physiology. The primary goals are to hydrate the flower and reduce ethylene gas effects and bacterial growth. After harvesting, condition the stems by allowing them to hydrate deeply in a cool, dark place for several hours or overnight. Recutting the stems underwater can prevent air embolisms if they have been out of water for any period. Adding a commercial floral preservative to the vase water is highly beneficial. These preservatives contain three key components: a biocide to inhibit bacteria that clog the stem, sugar to nourish the flower (replacing lost photosynthesis), and an acidifier to lower the water's pH, which improves water uptake. Calla Lilies are sensitive to ethylene gas, a plant hormone that accelerates aging (senescence), so they should be kept away from ripening fruit and exhaust fumes.
