Cacti are survivors. When you think about the environmental challenges that these succulents endure, they're amazing organisms. Understandably, you’d be concerned about your cactus if you notice it starting to brown. Rest assured that your plant isn’t sick or dying. Instead, you’re seeing a vital part of its adaptations to protect itself.
Corking describes the process by which the green, fleshy tissue of a plant will convert to a brown-colored, firm texture. A cactus will lose its spines, too. It typically begins at the base and eventually works its way up the length. It’s an aging mechanism that can also occur because of stress. That could stem from coarse sand scratching the plant’s surface or simply supporting new growth.
Corking can happen so gradually that you may not even notice it happening. However, it shows a crucial part of plants’ survival. These species began life in the water. When they moved to land, plants had formidable trials to overcome, namely, water loss and foraging by herbivores. They eventually adapted with the evolution of unique cells containing a substance called suberin.
You can think of it as a plant’s bandage if it gets damaged. While they grow slowly, species such as the Monstrose Cactus will need the extra support that this fat-containing chemical contains. The wood-like appearance of your plant provides just what it needs to continue growing. You’ll even see it on columnar species, like the Peruvian Apple Cactus because of the extra weight of its fruit.
Other Causes of Browning
While corking isn’t a significant concern, other conditions that cause your cactus to turn brown can point to serious issues. For example, a plant in poorly drained soils can develop rot. The difference is the texture. Whereas corking feels firm, rot is soft and squishy. The cactus will take on a disagreeable odor as its flesh decays.
Insect pests can cause a similar appearance. Unless something pierces that protection, the cactus' flesh and spines provide excellent protection. Mites and mealybugs are bad enough on their own. However, they also leave breeches in the flesh where bacteria, fungi, or viruses can enter. The combined forces of the pests and disease will kill a plant quickly, causing the same effects as rot.
Corking is a long work in progress, so you likely won’t catch it until it is well underway within your cactus. You can try cutting off the browned areas, but you may risk damaging the plant. The best way to slow its onset is to give your cacti as stress-free an environment as possible. That means watering them when needed and keeping them in pots with suitable drainage.
Direct sunlight can also harm your plants. UV radiation can cause sunburn just like it can for you if you spend too much time soaking in the rays. Indirect light is a better solution.
While it might appear problematic, corking is a cactus’ means of protecting it from damage and stress. It helps a plant to be able to handle the weight of its growth. Cacti might struggle to survive environmental pressures without it. As long as you’re giving your plants proper care, you needn’t worry about it.