Yellowing leaves on a succulent, known as chlorosis, signal that the plant is under stress and struggling to produce chlorophyll. Succulents are sensitive to imbalances in their care routine, storing water in their thick leaves and stems. This discoloration is a warning sign that the plant needs immediate adjustment. Understanding the distinct visual clues associated with different stressors is the first step toward correcting the issue.
The Primary Cause: Excess Water and Root Damage
The most frequent cause of yellowing leaves in succulents is excess water, which leads to cellular damage and root rot. Succulent leaves that have turned yellow due to overwatering will often appear translucent, puffy, and mushy to the touch. This happens because the plant’s cells absorb more water than they can safely hold, causing them to burst and the leaf structure to collapse.
When soil remains saturated for too long, the roots are deprived of oxygen and begin to die, leading to root rot. Rotted roots become soft, brown, or black, preventing the plant from absorbing necessary nutrients and water. To check for this, insert a clean wooden skewer or finger deep into the soil; if it comes out damp, excess moisture is the likely culprit. Proper drainage holes in the pot are necessary to ensure water can escape.
Light and Temperature Stress
Improper light exposure can also trigger yellowing. If a succulent is placed in a location with insufficient light, its growth may become pale and elongated, a process called etiolation. Chronic low light can result in the lower, older leaves turning pale yellow and dropping off as the plant conserves energy.
Conversely, too much intense, direct sunlight can cause a sunburn. This damage typically appears as bleached yellow, white, or brown patches on the parts of the leaves that face the sun. Sudden dips in temperature, particularly below 40 to 45°F, can also shock the plant, causing cells to freeze and rupture, resulting in yellow or black, mushy damage.
Nutrient Deficiencies and Soil Health
A lack of specific nutrients or poor soil conditions can cause leaves to yellow. Soil that has been used for a long time can become compacted, restricting the air pockets that roots need to breathe. Over time, the limited volume of soil in a pot can also become exhausted of macro and micronutrients.
A deficiency in nitrogen, a building block of chlorophyll, typically causes a generalized pale yellowing that starts in the oldest, lower leaves. Other mobile nutrients like magnesium can also cause yellowing between the leaf veins of older foliage. These deficiency-related symptoms are usually a uniform yellowing.
Immediate Steps for Plant Recovery
The first action is to diagnose the root cause and immediately stop watering if excess moisture is suspected. Carefully remove the plant and inspect the roots; if they are brown and mushy, use sterilized scissors to trim away all affected root and stem tissue. Repot the plant into a new container with fresh, well-draining succulent or cactus mix. Do not water it for several days to allow any cuts to callus.
If the issue is light-related, move the plant gradually to a better location. A plant suffering from sun scorch should be moved to an area with bright, indirect light, while a plant that is pale from low light needs slow acclimatization to a brighter spot. For nutrient issues, repotting the plant into fresh soil is often the simplest solution, or a diluted fertilizer can be applied sparingly during the growing season. Moving forward, adopt the “soak and dry” watering method, only watering thoroughly after the soil has completely dried out.