Yellowing leaves on a calla lily indicate the plant is experiencing stress, often due to environmental factors or care practices. Understanding the underlying causes behind this discoloration is the first step toward restoring your calla lily’s vibrant green foliage and promoting its overall health.
Diagnosing Yellow Calla Lily Leaves
The pattern of yellowing on your calla lily’s leaves provides clues about the problem. Examine if yellowing affects older leaves, newer leaves, or the entire plant, noting if discoloration appears uniformly or is concentrated on leaf tips, edges, or between veins. Check soil moisture by inserting your finger an inch or two into the soil. Inspect leaves and stems for pests like small insects or webbing, and consider the plant’s environment, including light exposure and temperature.
Common Reasons for Yellowing and Their Solutions
Watering Problems
Overwatering often causes yellowing leaves and root rot. Waterlogged soil deprives roots of oxygen, causing them to decay and appear mushy, which prevents nutrient absorption and leads to yellowing, often starting with lower leaves, and sometimes wilting. Underwatering also causes yellowing, typically resulting in dry, crispy leaves, often at the edges. To address this, plant your calla lily in a pot with drainage holes and well-draining potting mix. Water only when the top inch or two of soil feels dry, allowing excess water to drain completely.
Light Issues
Both excessive and insufficient light contribute to yellowing foliage. Too much direct sunlight, especially intense afternoon sun, can scorch leaves, leading to pale yellow or bleached spots. A lack of light results in overall yellowing and leggy growth. Calla lilies thrive in bright, indirect light; an ideal location is near a north or east-facing window for gentle morning sun, avoiding harsh afternoon rays. If natural light is limited, supplement with a grow light.
Nutrient Deficiencies
Yellowing leaves can indicate a lack of essential nutrients, known as chlorosis. Nitrogen deficiency often causes general yellowing of older leaves, as nitrogen is vital for chlorophyll production. Iron deficiency causes yellowing between the veins of newer leaves while veins remain green. To correct this, apply a balanced fertilizer every few weeks during the growing season. Follow application rates to prevent over-fertilization, which can lead to salt buildup and plant stress.
Temperature Stress
Calla lilies are sensitive to extreme temperatures; fluctuations can cause leaves to yellow. Both cold conditions (below 50°F/10°C) and prolonged high heat stress the plant. The optimal temperature range is 60°F to 75°F (15°C to 24°C). To prevent stress, position your plant where temperatures remain stable, away from cold drafts or direct heat sources.
Pests and Diseases
Pests and diseases can cause calla lily leaves to yellow. Common pests like aphids, spider mites, and mealybugs feed on plant sap, leading to yellowing, distorted leaves, or stippling; spider mites specifically cause tiny white or yellow spots and fine webbing on leaf undersides. Fungal infections, such as root rot or leaf spot diseases, also lead to yellowing, wilting, or dark spots. Address pests by washing the plant with a mild soap solution or using insecticidal soap. For diseases, improve air circulation, avoid overhead watering, and ensure proper drainage.
Natural Leaf Cycle
Yellowing leaves can be a normal part of the calla lily’s life cycle. As the plant prepares for dormancy, typically after flowering, older, lower leaves may naturally yellow and die back. This conserves energy for the next growth cycle. If yellowing is confined to older leaves, new growth remains healthy, and the plant has recently bloomed or is nearing its resting period, it is likely natural. During this time, reduce watering and allow foliage to die back naturally.
Preventing Future Yellowing
Preventing future yellowing requires consistent attention to your calla lily’s environmental needs. Ensure the plant receives bright, indirect light, as proper illumination is crucial for healthy foliage. Establish a regular watering routine, allowing the top inch or two of soil to dry between waterings to prevent both overwatering and underwatering, and always use a well-draining potting mix with adequate drainage holes. During the growing season, provide balanced nutrition by fertilizing once a month with a suitable plant food. Regularly inspect for early signs of pests or diseases, addressing them promptly, as a stable temperature range and good air circulation also contribute to plant vigor and resistance to stress, helping to keep leaves green and vibrant.