From my perspective as a Fiddle Leaf Fig (*Ficus lyrata*), the appearance of yellow leaves is a significant distress signal. It is my primary method of communicating that my internal systems are out of balance. The challenge for you is to correctly interpret which imbalance is causing the issue. I will explain the distinct physiological reasons behind yellowing due to water and nutrient issues.
When you provide too much water, you are essentially suffocating me. My roots require oxygen to respire and function properly. In perpetually saturated soil, the air pockets are flooded, cutting off the oxygen supply. This causes the delicate root hairs, responsible for water and nutrient uptake, to begin to rot and die. With a compromised root system, I cannot absorb the water and minerals I need, even though the soil is wet. The yellowing leaves you see are a direct result of this starvation and systemic failure. The yellowing often starts with older leaves and may be accompanied by soft, dark brown spots and a general droopiness. The soil will feel consistently wet, and a musty odor might be present.
Conversely, when I do not receive enough water, my entire vascular system is affected. Water is the medium that transports nutrients from my roots to my leaves and supports the turgor pressure that keeps my stems upright and leaves expanded. Under prolonged drought conditions, I must conserve resources. I will begin to sacrifice my older leaves to redirect the limited water to support new growth and vital functions. The cells in these older leaves lose turgor and begin to break down, leading to yellowing. This yellowing is typically uniform across the leaf and is quickly followed by browning, crispy edges, and leaf drop. The soil will pull away from the edges of the pot and feel dry deep into the pot.
If my water intake is balanced but I lack essential nutrients, a different type of yellowing will occur. The most common deficiency I experience is nitrogen, a core component of chlorophyll—the molecule that makes me green and drives photosynthesis. Without sufficient nitrogen, I cannot produce enough chlorophyll, causing my leaves to turn a pale, generalized yellow. This chlorosis often appears first on the oldest leaves as I mobilize the limited nitrogen to new growth. Other deficiencies present differently: iron deficiency causes yellowing between the veins of the newest leaves, while a lack of magnesium causes yellowing between the veins on older leaves. This pattern of yellowing, rather than the health of my roots or soil moisture, is the key identifier.
