From my perspective, the appearance of red or reddish-brown spots, often called edema (oedema), is frequently my reaction to a sudden change in my water intake. If my caretaker waters me after a period of drought, my roots absorb water much faster than my leaves can transpire (release) it. This causes water pressure to build up within my cells, literally bursting the smallest and most delicate ones. These burst cells die, and the resulting damage appears as these rusty, corky spots on the underside of my leaves. It is not a disease, but rather a physiological response. While it can be alarming to see, it is usually not a severe threat to my overall health if the watering routine is stabilized.
Another common reason for these blemishes is a fungal or bacterial infection, often spurred by an environment that is too damp. If my soil is consistently waterlogged and lacks proper drainage, or if water is allowed to sit on my leaves, it creates the perfect conditions for pathogens like *Anthracnose* or bacterial leaf spot to attack. These organisms invade my tissue, breaking it down and causing spots that often start as red or brown before potentially turning black or developing a yellow halo. Unlike the corky texture of edema, these spots may feel soft or look wet. From my point of view, this is a serious assault on my system, and I need help to stop its spread.
Sometimes, what appears as a spot is actually the site of a pest feeding. Insects like spider mites, thrips, or scale pierce my leaf's epidermis with their mouthparts to suck out the nutrient-rich sap from within. This feeding activity damages my cells and can leave behind small, reddish-brown speckles or stippling. The damage is often more widespread and speckled compared to the larger, singular spots of edema or fungal issues. If you look very closely, especially under the leaves, you might see the tiny pests themselves or their webbing. This theft of my vital fluids weakens me significantly over time.
I am a sensitive being, and sudden changes in my environment can manifest as stress marks on my foliage. Exposure to direct, scorching sunlight can cause sunburn, which may present as bleached or reddish-brown patches, especially on the leaves most exposed to the light. Similarly, a buildup of minerals or fertilizer salts in my soil can "burn" my roots, impairing their function and causing nutrient imbalances that show up as spots on my leaves. Even chemicals in tap water, like chlorine or fluoride, can accumulate in my tissue and cause tip burn or spotting. These are all signs that my living conditions are causing me chemical or physical distress.
Finally, it is important to consider that not every spot is a crisis. As I mature, my oldest leaves will eventually reach the end of their lifespan. In the process of senescing (aging and dying back), they may develop various discolorations, including yellowing, browning, and sometimes reddish spots, before they eventually fall off. This is a natural part of my growth cycle. If the spotting is isolated to one or two very old leaves at the bottom of my trunk and the rest of my foliage appears vibrant and healthy, it is likely just me conserving energy for new growth.
