From our perspective, water is the river of life that flows through our tissues, carrying nutrients and keeping our cells turgid. When our roots cannot access sufficient water, it creates a crisis. The farthest points from the roots—our leaf tips—are the first to suffer. The cells there dehydrate and die, turning brown and crispy. This can happen for two main reasons: you are simply not providing enough water, or our root system is compromised and cannot absorb it effectively. Conversely, if our roots are left sitting in saturated, oxygen-deprived soil, they will rot and die. A dead root system cannot take up water at all, leading to the same symptom of drought stress: brown leaf tips.
You may be trying to help with a nutrient boost, but an overly generous or too-frequent application of fertilizer is, from our point of view, a chemical assault. The high concentration of mineral salts in synthetic fertilizers can actually draw water out of our root tissues through osmosis, effectively burning them. This root damage immediately disrupts our ability to hydrate ourselves, and the excess salts accumulate in the leaf margins and tips, causing them to scorch and turn brown. We are particularly sensitive to this; we prefer a gentle, balanced diet rather than a strong, concentrated one.
Our leaves are constantly engaged in a process called transpiration, releasing water vapor into the air. In an environment with very low humidity, the rate of water loss from our leaves can exceed the rate at which our roots can draw up water from the soil. This creates an internal drought. The leaf tips, being the most vulnerable extremities, dry out first. Similarly, if we are positioned in direct, hot sunlight or exposed to harsh, drying winds, the excessive transpiration can literally scorch our foliage, causing the same characteristic browning at the tips and edges.
Beneath the soil surface, a silent battle may be raging. Fungal pathogens like Phytophthora and Pythium are notorious for attacking our root systems. These organisms cause root rot, which blocks the vascular tissues that transport water and nutrients up into our stems and leaves. From our perspective, it is as if our main water pipeline has been severed. The above-ground symptoms are a direct cry for help: wilting, yellowing, and of course, the progressive browning of leaf tips as the water supply is cut off, even if the surrounding soil feels moist.
