An aloe vera plant’s natural state is a vibrant, fleshy green, but a change to a brown, red, or yellow hue is a common distress signal. This discoloration is the plant’s defense mechanism against environmental stress. The shift in color is not a disease but a direct reaction to an imbalance in its care. The plant is signaling that its environment needs adjustment, most often related to light, water, or temperature. The specific shade and texture of the browning can help you quickly pinpoint the exact problem.
Sunburn and Light Stress
Aloes are sun-loving succulents, yet they can be overwhelmed by a sudden increase in light intensity. This commonly occurs when an indoor aloe is moved outdoors without gradual acclimatization. The resulting damage is often referred to as “stress color” rather than true sunburn, appearing as a uniform reddish-brown or bronze blush across the exposed surfaces of the leaves. This color change is the plant producing protective pigments to shield its inner tissues from excessive ultraviolet radiation.
True sunburn manifests as permanent, bleached-out or white patches, occurring when the plant is exposed to harsh, direct light for too long, such as in an unshaded south-facing window. When stressed by light, the leaves feel tough and dry, sometimes with crispy tips, but they maintain their firmness. The stress color is a warning sign that the plant needs a less intense light environment to prevent irreversible tissue damage.
Overwatering and Root Issues
Overwatering is the most frequent cause of fatal browning in aloe plants, leading to root rot. This damage is distinctly different from sun stress, presenting as a dark brown or black discoloration that typically starts at the base of the leaves where they meet the soil. The affected leaves feel soft, mushy, and translucent because their internal cells have burst from excessive water absorption and decay.
The underlying problem is a lack of oxygen in the soil that suffocates the roots. Saturated soil pushes out the air pockets the roots need to breathe, causing them to decay and creating an ideal environment for fungal pathogens. This rot then travels upward into the leaves, turning the plant into a soft, mushy mess that often emits a sour odor. Unlike browning from overwatering, severe underwatering causes leaves to shrivel, curl inward, and develop brown, crispy tips as the plant draws moisture from its own tissues.
Cold Temperatures and Shock
Aloe plants are sensitive to cold, and exposure to temperatures below 50 degrees Fahrenheit can cause rapid tissue damage. This often happens when a plant is placed too close to a drafty window in winter or left outside too late in the fall. The cold shock causes a distinct type of browning or blackening that looks similar to freezer burn.
Affected leaf sections often appear waterlogged and mushy, sometimes becoming clear or translucent before turning dark. This damage is usually irreversible for the specific tissue that was frozen or chilled. Proximity to air conditioning vents, which blast the plant with a constant stream of cold air, can also cause this damage.
Steps for Recovery and Prevention
When browning is noticed, the first step is a diagnostic check of the soil and roots. Gently unpot the plant to inspect the root system; healthy roots should be firm and white or light-colored. If the roots are black, slimy, and fall apart easily, severe root rot has set in, and you must trim away all damaged tissue using a sterilized blade.
To address light or temperature stress, immediately move the plant to a location with bright, indirect light, away from direct midday sun or cold drafts. For long-term health, ensure your plant is potted in a container with a drainage hole and use a gritty, fast-draining soil mix designed for succulents. A proper watering schedule means only watering thoroughly after the soil has dried out completely, preventing the recurrence of the most common cause of browning.