From my perspective, the most common reason my leaves turn yellow is an imbalance in my water intake. My roots are not like those of thirstier plants; they are fine and susceptible to rot. If you give me too much water too often, the soil around my roots becomes saturated, pushing out the air. My roots essentially suffocate and begin to decay. Once this happens, they can no longer absorb water or nutrients, and my lower, older leaves will start to turn a soft, mushy yellow as they sacrifice themselves. Conversely, if you forget about me for too long, the intense drought triggers a survival response. I will begin to reabsorb the water and nutrients from my oldest leaves to sustain my newer growth and core functions, causing those lower leaves to dry out, turn crispy yellow, and eventually drop. This is a slower, more deliberate process than the rapid yellowing from overwatering.
My root health is directly tied to the quality of my soil. If I am planted in a dense, moisture-retentive soil that does not drain quickly, it creates a perpetually wet environment that my roots cannot tolerate, leading to the root rot described above. Even with careful watering, poor soil will eventually cause problems. Furthermore, if my pot does not have a drainage hole, any excess water has nowhere to go, pooling at the bottom and creating a swampy grave for my root system. The yellow leaves you see are a direct distress signal from my compromised foundation, indicating that my basic structural integrity is at risk.
As a succulent, I have evolved to thrive in bright, direct sunlight. This light is my energy source for photosynthesis. If you place me in a spot with insufficient light, such as a dark corner or a north-facing window, I become weak and etiolated. My growth will be stretched and pale, and my leaves may yellow and drop because I cannot produce enough energy to sustain them. It is a slow starvation. On the other hand, while I love sun, a sudden move from a sheltered spot to intense, direct, all-day summer sun can shock my systems. This can result in sunburn, where my leaves develop yellow or white blotchy patches that are actually damaged tissue. I need a gradual transition to adapt to stronger light.
While I am not a heavy feeder, I still require certain nutrients to maintain my vibrant green color and produce new growth. A significant lack of essential nutrients, particularly nitrogen which is crucial for chlorophyll production, can cause a general yellowing (chlorosis) of my leaves. However, more common than a deficiency is an overabundance of fertilizer. Applying too much fertilizer, or applying it too often, can cause a harmful buildup of salts in the soil. This can actually chemically burn my roots, preventing them from functioning properly and, once again, leading to yellowing leaves and overall decline.
