Question
Saguaro cactus about 6
My son was given a potted saguaro cactus about 7 years ago. It is in a south facing window (we live in New England). It has about doubled in size and he recently repotted it. It was watered infrequently (about 1 tablespoon per month when it was in the 2" pot). About a year ago the base began turning whitish, now there is also a white spot further up around the spines. The white part doesn't seem to be any softer than the rest of the plant. I told him we probably couldn't keep it alive long (I'm surprised it's lasted this long). Is it rotting or is this to be expected? Thanks.
AnswerDear Judy,
I'm not sure. The white/tan at the base could be normal corking that older cacti develop at the base as part of aging. The white spot further up looks like it has some black rot. How did the roots look when it was repotted? Black, brown, with the casting coming off is unhealthy. Fat, whitish roots are OK. The blackish area around the spine that looks like rot could have occurred as a result of transplant. Sometimes even a minor insult to a spine or slit in the skin that you don't even notice at the time can let in pathogens. Also, whenever you repot don't water the plant for a few days so any tiny slits, etc. can callous over.
If it was my plant, I'd check the roots again, make sure the plant isn't at all mushy or hollow at the base and replant it in a soiless mix of spagnum, perlite, and some sterilized potting soil at a 2:2:1 ratio in a pot that is 1/3 the height of the plant but not much wider.
Before you do that, take a sterilized (with alcohol) sharp knife and cut around that spine. If you need to cut really deeply, then i would consider starting a new plant from above that where the tissue is healthy. If it isn't too deep, I'd remove the rot and dust the tissue with fungicide. It will be scarred there, but hopefully you've removed the rot.
If you need help on starting a new plant let me know.
Maureen
