I have a very old Christmas cactus (50 years old). It is in a very small pot. It has lots of blooms several times a year. My question is: I have noticed over the past couple of years that I am seeing a red bulb growing from a leaf and then a leaf to follow. What is this red bulb. It is not a flower. It is telling me something?
Without seeing a picture of this, I really can't say what it could be. Is it always on the same leaf?
It's possible that this ancient plant is experiencing some issues with some kind of genetic anomaly, similar to cancer in humans. Usually these occur around the base of the plant, or even under the soil.
Other similar things are galls, which can be caused by insect damage, or a bacteria. These are known also as bacterial canker or crown gall.
If it's really unsightly, you can prune it off, and it will hopefully revert back to regular new growth.
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