From my perspective as a Crassula, water is a constant negotiation. My succulent leaves are designed to store water for dry periods. When you provide too much water, the soil becomes saturated, suffocating my roots. Without oxygen, the root cells die and can no longer absorb water or nutrients. This creates a paradox: my leaves, sitting in wet soil, begin to show signs of drought. The cells in the leaves, particularly older ones, break down and die, manifesting as soft, mushy, dark brown spots, often starting at the base of the plant. Conversely, if you provide too little water for an extended period, the extreme dehydration will cause my leaf tissues to desiccate and die, resulting in dry, crispy, lighter brown spots. I am telling you that my watering needs change with the seasons; I need far less in my dormant winter period than in my active summer growth phase.
While I am a sun-loving plant, I am not immune to sunburn. If I am moved too abruptly from a lower light area into intense, direct sunlight—especially the hot afternoon sun—my leaves cannot adapt quickly enough. The intense ultraviolet radiation damages the chloroplasts within my leaf cells, effectively killing those cells. This damage appears as flat, smooth, light brown or beige patches, typically on the upper surfaces of the leaves that are most exposed to the light. This is not a disease but a form of scarring. Once a leaf is sunburned, the damage is permanent. I prefer a gradual introduction to stronger light to allow my photosynthetic machinery to build up protective pigments.
The appearance of spots can sometimes indicate a pathogenic attack. These spots often differ from environmental causes; they may have yellow halos, be sunken or raised, and can spread rapidly under favorable conditions. Fungal issues, like leaf spot or anthracnose, are frequently a secondary problem. They exploit weakness caused by the primary issue: overwatering. Consistently wet leaves and high humidity create a perfect environment for fungal spores to germinate and invade my tissues. Bacterial infections, which can cause soft, rotten spots, often enter through wounds or are splashed onto leaves from contaminated soil. My message here is that healthy Crassulas in the right conditions are remarkably resistant; pathogens are usually a symptom of an underlying environmental stress.
Small, brown spots can sometimes be the work of tiny pests. Sap-sucking insects like scale insects attach themselves to my stems and the undersides of leaves. They appear as small, brown, bumpy spots themselves, and their feeding activity damages the leaf tissue, often leaving a discolored mark where they have sucked out the nutrient-rich sap. Other pests like spider mites cause stippling—tiny yellow or brown spots—as they pierce individual cells. This damage weakens the leaf and can create entry points for diseases. I would appreciate it if you would regularly inspect my nooks and crannies, as catching these invaders early makes their eviction much simpler.
A less common but specific cause of spotting is a condition called edema (oedema). This occurs when I absorb water through my roots faster than I can lose it through transpiration (evaporation from my leaves). This often happens during cool, cloudy, humid weather when the soil is warm and moist but the air is saturated, limiting transpiration. The excess water pressure causes cells in my leaves to burst. These damaged cells then die and form crusty, corky, brown or rust-colored spots, usually on the undersides of the leaves. This is a clear sign of a watering schedule that is out of sync with the current environmental conditions and my growth rate.
