One of the branches that looks like a small tree trunk on my Christmas cactus is getting soft and the tree bark is peeling near the soil. I haven't over watered; I give it water when it feels dry. About a month ago, I took it to a nursery, carefully, so as not to break any of the branches. I was told it needed to be watered, but again one of the branches had to be taken out of the soil because I was told it was rotting. This is a little over a month ago, since then I watered the cactus one more time sparingly. A few days later (about a week), I watered it again and added very little water. The leaves seem to be ok, not limp, but the softness or rot seems to be advancing on that particular branch, which is relatively large. I don't want to lose any more branches and would hate to see anything happen to it. Please advise what to do.
Caring for Christmas Cactus
Certified GKH Gardening Expert
It sound like root rot fungus has set in. Mostly it occurs when it is overwatered, but it can happen even without overwatering. I would treat the soil with a fungicide. This article may also help:
You may want to start a few new plants, just in case. This article will help with that: