What’s the problem?
My prickly pear (Opuntia) cactus is developing raised brown patches on both sides of the stem that are spreading, though the plant is still growing. Should I be worried?
Diagnosis
Those circular brown patches are a classic sign of corking. This is a natural process in many cacti, which causes the lower stem to gradually harden and turn brown, like the bark on a tree. It usually starts at the base and slowly works its way up as the plant matures. While the rough texture can look alarming, it doesn’t harm the plant. However, because corking can be confused with a fungal infection or pests such as scale insects, it’s worth a closer look. Scale insects will appear as raised, uniform bumps that can be scraped off, whereas corking is part of the stem tissue itself and cannot be removed.
Prescription
If the patches are firm and part of the stem, no treatment is required; it’s simply a sign of maturity. Continue caring for your cactus as usual with bright light, well-draining soil and cautious watering.
Prevention
Corking can’t be prevented as it’s part of the natural lifecycle of cacti. As long as there’s healthy growth at the tips, don’t worry. The contrast between the corky base and green growth will become part of the plant’s character over time.
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