From the plant's perspective, yellowing leaves can be a normal part of the Calla Lily's life cycle. Older leaves, especially those at the base of the plant, naturally turn yellow and die as the plant redirects energy to new growth. This is a survival mechanism to prioritize younger, more efficient leaves for photosynthesis. If only the lower leaves are affected and the rest of the plant appears healthy, this is likely the cause.
Calla Lilies are sensitive to both overwatering and underwatering. Overwatering can lead to waterlogged soil, suffocating roots and preventing oxygen uptake. This causes root rot, which manifests as yellowing leaves. Conversely, underwatering stresses the plant, reducing its ability to transport nutrients, leading to yellow, wilted leaves. The plant signals distress by sacrificing older leaves to conserve water for vital parts.
Yellowing leaves may indicate a lack of essential nutrients, particularly nitrogen, iron, or magnesium. Nitrogen deficiency typically causes uniform yellowing of older leaves, while iron deficiency results in yellowing between the veins of younger leaves. Magnesium deficiency shows as yellow patches between leaf veins. The plant prioritizes nutrient distribution to new growth, leaving older leaves to yellow and die.
Calla Lilies thrive in bright, indirect light. Too much direct sunlight can scorch leaves, causing yellow or brown patches as the plant's tissues are damaged. Insufficient light, on the other hand, reduces photosynthesis, leading to pale or yellow leaves as chlorophyll production declines. The plant adjusts its leaf structure to optimize light absorption, but extreme conditions overwhelm its adaptive capacity.
Calla Lilies prefer stable temperatures (60-75°F or 15-24°C) and moderate humidity. Sudden temperature drops or drafts can shock the plant, causing leaves to yellow and drop. Low humidity dehydrates leaves, leading to yellow edges or tips. The plant responds by reducing leaf surface area to minimize water loss, resulting in yellowing.
Pests like spider mites or aphids suck sap from leaves, weakening the plant and causing yellow spots or streaks. Fungal or bacterial infections, such as root rot or leaf blight, disrupt nutrient flow, leading to yellowing. The plant may sacrifice infected leaves to contain the spread, redirecting resources to healthier tissue.
Calla Lilies prefer slightly acidic to neutral soil (pH 6.0-6.5). If the soil is too alkaline or acidic, the plant cannot absorb nutrients efficiently, leading to yellow leaves. The plant's root system struggles to uptake iron or manganese in high-pH soils, resulting in chlorosis (yellowing with green veins).
If recently repotted, the plant may experience stress as it adjusts to new soil conditions. Root disturbance can temporarily impair nutrient and water uptake, causing yellow leaves. The plant focuses energy on root regeneration, leaving older leaves to yellow until stability is restored.
Overuse of fertilizers or exposure to herbicides can burn roots or leaves, causing yellowing. The plant's cells are damaged by chemical toxicity, disrupting normal functions. In self-defense, it sheds affected leaves to prevent further harm.
