My 30+ yr old Christmas cactus has never been repotted, but the foliage is well within range for the 5" pot. Although it blooms fine every year and foliage is the usual green, I'm concerned about:
1) chunks of foliage (up to 6" long and 4" wide) often fall off without being touched. There appears to be no pathology on either side of the break, and both the remaining and shed portions appear equally healthy and consistent with the rest of the plant.
2) there are some brown spots on some sections of the plant varying from 1/16" to 1/4" but have not found any pix similar online. It also does not appear to affect blooming at tips, nor are they present on the sections which have fallen off (or on the remaining branch). Sorry, not digital. Any thoughts?
Anne Arundel County Maryland
1) Christmas cactus propagate themselves from sections that separate from the plant and these short sections can separate easily. This may simply be the plant attempting to reproduce.
It's possible that overwatering could be associated with breakage. Though the plants need plenty of water, they should not be in soggy, waterlogged soil, and after flowering they need a rest period when water should be cut back. The top 1/2 inch of soil can dry out between waterings from then until new growth appears in spring.
2) Brown spots could be scale (photos online). Also, older foliage does get woody and brown toward the base.
If you see additional symptoms, you can let us know.