The Aloe vera plant is a popular succulent known for its hardiness. However, it can exhibit signs of distress, most commonly yellowing leaves, a condition called chlorosis. This discoloration signals that the plant’s ability to produce chlorophyll is compromised, often due to an environmental imbalance. Identifying the root cause is the first step toward restoring the plant’s health.
Water and Root Environment Issues
The most frequent cause of yellowing in Aloe vera plants originates in the soil and is linked to improper watering practices. As desert-adapted plants, Aloes store significant amounts of water in their fleshy leaves and have a low tolerance for persistently wet conditions. When the soil remains saturated, it creates an anaerobic environment that suffocates the roots and promotes pathogenic growth.
This condition leads to root rot, where the healthy, firm white roots turn mushy, dark brown, or black and lose their functionality. The damaged root system can no longer absorb water or essential micronutrients, such as iron and magnesium, from the soil. This nutrient deprivation prevents the plant from synthesizing chlorophyll, and the leaves begin to turn yellow, often starting at the base.
Poor drainage exacerbates the problem; a heavy, moisture-retentive potting mix or a container without adequate drainage holes traps water around the root ball. Consistent overwatering forces the plant into this state of decay, indicated by leaves that feel soft or translucent in addition to being discolored. Conversely, chronic underwatering can also cause yellowing, typically manifesting as shriveled, pale leaves as the plant draws moisture from older foliage to preserve new growth.
Light and Temperature Stressors
External environmental factors like light and temperature extremes can induce yellowing by interrupting cellular processes. Aloe vera thrives in bright, indirect light, but sudden exposure to intense, direct summer sun can cause photo-oxidative damage. This stress, known as sun scorch, causes the leaves to develop a pale yellow or even white discoloration that eventually turns brown and crispy.
This quick color change is the plant’s defense mechanism, reducing the amount of sunlight absorbed to prevent the destruction of cellular structures. The yellowing from sun stress usually appears across the entire exposed leaf surface and is distinct from the patchy, soft discoloration caused by root rot. This discoloration is a sign of permanent tissue damage.
Temperature extremes also place stress on the plant, with cold damage being a particular concern. Aloe vera suffers damage when temperatures drop below 50°F (10°C), and freezing temperatures are lethal. Exposure to cold causes the water stored within the leaf cells to expand and rupture the cell walls, leading to yellowing, translucent, and mushy spots on the foliage.
Remediation and Long-Term Prevention
Addressing yellowing requires a targeted approach based on the suspected cause, with root rot demanding the most immediate intervention. If root decay is suspected, the plant must be unpotted immediately, and the entire root system should be rinsed clean of soil. Use sterilized scissors or a sharp knife to prune away any roots that are dark, soft, or smell foul, cutting back to firm, healthy tissue.
After pruning, allow the plant to air-dry in a shaded, well-ventilated area for two to three days until the cut surfaces form a protective, dry layer called a callus. Repot the callused plant into a clean pot using a fresh, gritty soil mix specifically formulated for cacti and succulents, which contains materials like perlite or coarse sand to ensure rapid drainage. Using a terracotta pot is also advisable, as it helps wick away excess moisture from the soil.
For light-related issues, move the plant to a location that receives bright, filtered sunlight to allow the plant to recover without further scorching. If cold damage has occurred, remove the plant from the cold source and trim away the mushy, damaged leaf sections with sterilized tools. The most effective long-term prevention involves adopting a “soak and dry” watering method, only providing water when the top two inches of soil are completely dry.