What Causes Brown Spots on an Aloe Plant?

Brown spots on an aloe plant’s leaves are a signal that its environment or care routine needs adjustment. These discolorations vary in appearance, indicating a range of potential issues. Understanding the characteristics of the spots is the first step toward diagnosing the cause and restoring your plant’s health.

Improper Watering and Sun Exposure

The most frequent reasons for an aloe plant to develop brown spots are its watering schedule and light conditions. Overwatering is a primary concern for succulents. When an aloe is overwatered, the leaves may become soft and mushy, developing dark brown areas that often start from the base. This is a sign of root rot, where roots decay in overly wet soil and can no longer absorb nutrients.

To address overwatering, allow the soil to dry out completely before watering again. Check the soil’s moisture a few inches below the surface; if it feels damp, wait longer. Ensure the pot has adequate drainage holes to prevent water from pooling. A terra cotta pot can also help wick away excess moisture from the soil.

Underwatering can also cause browning, though the appearance is different. The leaves will feel dry and wrinkled, with brown, crispy tips or edges. The solution is to water more thoroughly, not more frequently. When you water, saturate the soil until it runs out of the drainage holes, then let it dry completely before the next watering.

Sunburn is characterized by large, bleached, or scorched brown patches on leaves that face the sun. This occurs when the plant is exposed to harsh, direct sunlight. Aloe plants thrive in bright, indirect light. If you notice signs of sunburn, relocate the plant to a spot with filtered sunlight, such as near a window with a sheer curtain.

Fungal Diseases

Brown spots can be a symptom of a fungal infection. A common issue in aloes is Aloe Rust, which begins as small, yellow spots on the leaves. These spots develop into raised, circular, reddish-brown pustules that contain powdery spores.

This fungus thrives in cool, damp conditions with poor air circulation. If you suspect Aloe Rust, isolate the plant to prevent it from spreading. Use a sterile knife to remove all infected leaves at their base. Water the soil directly to keep the leaves dry and improve air circulation around the plant. For persistent infections, a copper-based fungicide can be applied according to product instructions.

Pest Infestations and Physical Damage

Small brown or yellow spots can be the result of pest activity. Sucking insects, such as scale or mealybugs, feed on the plant’s sap, leaving behind small, discolored dots. These pests can be removed by wiping them off with a cotton swab dipped in rubbing alcohol.

Not all brown spots are a sign of a problem. If a leaf is bent or scratched, the plant may form a brown, scar-like spot as part of its healing process. This type of mark is cosmetic and does not harm the plant’s overall health.