The elegant Zantedeschia, commonly known as the Calla Lily, is admired for its sculpted leaves and striking blooms. When these leaves begin to turn brown, it signals a change in the plant’s environment or care routine. Browning foliage communicates distress, and diagnosing the visual symptoms helps quickly address the underlying cause to restore the plant’s health.
Cultural Causes: Water, Soil, and Fertilizer
The most frequent causes of browning foliage are issues within the root environment, specifically related to moisture management. Overwatering is a common culprit, leading to root rot where the leaves display a soft, often mushy browning alongside a yellowing, which usually starts at the leaf tips and spreads inward. This occurs because saturated soil starves the roots of oxygen, allowing fungal pathogens to destroy the root tissue, preventing the uptake of water.
Conversely, underwatering causes leaves to brown rapidly and become brittle or crispy, particularly along the margins. When the soil dries out completely, the lack of moisture causes leaf cells to collapse and desiccate. The Calla Lily requires consistently moist but never soggy soil, allowing the top inch or two of the growing medium to dry before rewatering.
Soil that lacks adequate drainage exacerbates overwatering symptoms, as the dense structure retains too much moisture around the rhizomes. Fertilizer burn manifests as scorched, brown edges or tips on the leaves. This is caused by an excessive buildup of mineral salts in the soil, which creates a high concentration that draws water out of the plant’s roots through reverse osmosis.
Environmental Stressors: Light and Temperature
External conditions, such as light intensity and temperature, can directly injure the foliage. Intense, unfiltered light, particularly hot afternoon sun, can cause sunscald, leaving dry, bleached, or brown patches on the exposed leaf surface. This damage is a localized injury where the sun’s energy overheats and destroys the plant’s chlorophyll and tissue.
As a tropical plant, the Calla Lily is sensitive to cold temperatures and drafts. Exposure to temperatures consistently below 50°F (10°C) can induce cold shock, causing leaves to wilt and turn brown rapidly. This sudden cellular damage often results in complete dieback of the above-ground growth. Maintaining a stable environment, away from cold windows or air conditioning vents, prevents this stress.
Identifying Pests and Diseases
Browning accompanied by specific patterns or textures often indicates a pest infestation or disease. Spider mites feed on leaf cells, leaving fine stippling—tiny white or yellow dots—that eventually merge into a bronzed or brown discoloration. A sign of severe infestation is the presence of fine, silky webbing, especially on the undersides of the leaves.
Aphids are sap-sucking insects that cluster on new growth and leaf undersides, extracting fluids and sometimes leaving behind a sticky residue called honeydew. Non-chemical treatment for both pests involves thoroughly coating the plant, including leaf undersides, with horticultural oil like neem oil or an insecticidal soap solution. Bacterial soft rot is a rapid and destructive disease that causes foliage to collapse, becoming slimy and mushy, often starting at the base of the stem or rhizome.
Managing Dormancy and Pruning
Sometimes, browning is a natural part of the Calla Lily’s life cycle. The plant naturally enters dormancy, typically after its main flowering season or when conditions become too dry or cool. During this phase, the leaves will naturally yellow and then brown as the plant redirects its energy into the underground rhizome for a resting period.
Once a cultural or environmental cause has been identified and corrected, the damaged leaves should be removed. Pruning browning or dead foliage helps the plant redirect energy toward healthy new growth and improves air circulation. Use sharp shears sterilized with rubbing alcohol and cut the entire leaf stem cleanly at its base near the soil line.