Calla lilies are popular ornamental plants, valued for their elegant, trumpet-shaped flowers and attractive foliage. Their striking appearance makes them a frequent choice for gardens, containers, and floral arrangements. Successful cultivation begins with understanding their rhizomes, which are fundamental to their growth and vibrant blooming. The health of a calla lily plant is linked to the condition of its rhizomes, highlighting the importance of proper care.
Understanding Calla Lily Roots
Calla lilies grow from rhizomes, which are modified underground stems, distinct from true bulbs or conventional roots. These horizontal, fleshy structures store nutrients and carbohydrates, allowing the plant to survive dormant periods. Fibrous roots extend from the rhizomes, anchoring the plant and absorbing water and essential nutrients. The rhizome also produces new shoots, leading to foliage and flowers.
Calla lilies are rhizomatous perennials, a characteristic that influences their care requirements. Understanding that calla lilies grow from these specialized stems, rather than a typical root system, is important for proper planting and maintenance. This distinction helps in managing moisture levels and providing appropriate soil conditions.
Planting Calla Lily Rhizomes
For planting calla lily rhizomes, select a location with full sun to partial shade, ideally receiving at least six hours of direct sunlight for optimal blooming. In hotter climates, afternoon shade protects foliage from scorching. Calla lilies prefer rich, well-draining soil that is neutral to slightly acidic (pH 5.6-6.5). Amending the soil with organic matter like compost or well-rotted manure improves drainage and nutrient content.
Plant in spring after all danger of frost has passed and the soil temperature has warmed to at least 65°F.
In-Ground Planting
Rhizomes should be buried 1.5 to 4 inches deep with growing tips facing upwards. Space them 6 to 12 inches apart for proper growth and air circulation.
Container Planting
Choose pots with drainage holes, at least 6 to 12 inches in diameter, and use a high-quality, well-draining potting mix. Plant rhizomes 1 to 2 inches deep, spacing them 1 to 2 inches apart, or place three to five rhizomes in a 10-12 inch container.
After planting, water sparingly until shoots appear, then increase watering as the plant establishes.
Care for Calla Lily Rhizomes
Calla lilies prefer evenly moist soil but are susceptible to rhizome rot from overwatering. Allow the top inch or two of soil to dry out between waterings. Container plants typically require more frequent watering than those in the ground due to faster drying of the potting mix. During the growing season, deep watering ensures moisture reaches the entire root system.
Mulching in-ground plants with organic material helps retain soil moisture, suppress weeds, and provide a steady supply of nutrients. Fertilization supports vigorous growth and abundant blooms. A balanced, slow-release fertilizer (e.g., 10-10-10 or 20-20-20) can be applied at planting time. During the active growing season, liquid fertilizer can be applied monthly or every two to three weeks. Avoid high-nitrogen fertilizers, as this promotes foliage growth at the expense of flowers.
In colder winters (USDA zones 3-7), lift and store rhizomes indoors to protect them from freezing temperatures. Before the first hard frost, cut back foliage and carefully dig up rhizomes, shaking off excess soil. Store them in a cool, dark place (50-60°F) in a box with peat moss or sawdust, ensuring they remain slightly damp but not wet. Container plants can go dormant in their pots in a cool, unheated space.
Common Problems Affecting Calla Lily Rhizomes
Rhizome rot is a common issue, often resulting from overwatering or poorly draining soil. Symptoms include yellowing leaves, wilting despite moist soil, and a mushy or foul-smelling rhizome. To prevent rot, ensure effective drainage and allow the top layer to dry between waterings. If rot is detected, remove affected parts and repot the plant in fresh, well-draining soil.
Pests can also affect calla lily rhizomes. Common pests include aphids, spider mites, thrips, slugs, and snails, which can impact plant health. Regularly inspecting plants and addressing infestations with insecticidal soap or neem oil helps manage these issues. Good air circulation around plants also helps deter some pests and fungal diseases.