From my perspective as a begonia, brown spots on my leaves are not a disease in themselves but a symptom, a clear signal that my internal systems are under stress. These spots are areas of necrotic tissue, meaning the plant cells in that location have died. This necrosis is my way of sacrificing a small, compromised part to protect the whole. The causes are varied, but they all disrupt my ability to perform photosynthesis and respirate efficiently. Each type of spot—its location, pattern, and texture—is a clue to the underlying issue, be it an environmental imbalance, an invasion, or a cultural mistake made by my caretaker.
If the brown spots appear on the upper leaves that are most exposed, particularly those that are dry, crispy, and starting at the leaf tips or edges, the cause is likely too much direct sunlight. My leaves, especially the more delicate varieties, are adapted for bright, indirect light. Intense, direct sun acts like a magnifying glass, literally cooking the chlorophyll and delicate tissues within my leaves, causing sunscald. This damage is permanent for the affected cells. The solution is to move me to a location with bright but filtered light, perhaps behind a sheer curtain, where I can thrive without being scorched.
When brown spots are accompanied by yellow halos, appear in the center of leaves, or have a wet, mushy appearance, I am likely fighting a pathogen. Fungal issues like Botrytis (gray mold) or bacterial leaf spot thrive in stagnant, humid conditions. These organisms invade my tissue, breaking it down and causing rot. Overhead watering that leaves my foliage damp for extended periods is a common cause. To help me, you must improve air circulation around my foliage, avoid wetting my leaves when watering, and promptly remove any severely infected leaves to prevent spread. In severe cases, an appropriate fungicide or bactericide may be necessary.
Brown, soft, mushy spots often starting on the lower leaves near the soil line can signal a root problem, typically root rot caused by overwatering. My roots need both water and oxygen. When I am left sitting in saturated soil, my roots suffocate and begin to decay. This rot prevents them from taking up water and nutrients, which then manifests as brown, wilting spots on my leaves. The solution is to check my root ball. If the roots are brown and mushy, you must trim the damage, repot me in fresh, well-draining soil, and ensure my pot has adequate drainage holes. Adjust your watering routine to only hydrate me when the top inch of soil feels dry.
Sometimes, the spots are a reaction to what I am being fed. Brown, crispy leaf edges can indicate a buildup of salts from over-fertilization, which draws moisture out of my roots and leaves, effectively causing a chemical burn. Similarly, water that is high in chemicals like chlorine or fluoride can cause tip burn and spotting over time. To remedy this, flush my soil with plenty of clean, distilled, or rainwater to leach out excess salts. Ensure you fertilize me only during my active growing season and at half the recommended strength. Using filtered or collected rainwater for irrigation can prevent future chemical-related stress.
