Cactus/Discoloration on saguaro cactus
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Question
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.
![](javascript:displayImg('http://0.tqn.com/w/experts/Cactus-710/2010/06/Saguaro-cactus-6.jpg','Saguaro cactus about 6" tall','Base of cactus has been turning white over the past year or so.'))
Dear 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
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Maureen
Expertise
I can answer questions regarding the care and propagation of cactus and succulents and would actually group these together as folks often mistake one for the other and often their care is quite different. I also have a cold hardy cactus and succulent garden that has been quite successful. The subject in regard to classification of type is enormous and I wouldn't be able to answer all questions by any means. It is really IMPORTANT TO INCLUDE A PHOTO if at all possible and LET ME KNOW WHERE YOU ARE FROM, especially in terms of climate.
Experience
I have learned by reading books, by trial and error and by consulting with folks with much more knowledge. I have primarily grown C&S for the last 20 years.
Organizations
Cactus and Succulent Society of Massachusetts.
Education/Credentials
No formal training. See experience.
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