Cactus/Brown spots on San Pedro
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Question
I have several San Pedro and have suddenly noticed dark brown spots on all of them. I checked the roots and I don't see any root rot. The brown spots seems to be hard to the touch and not mushy. The tips were protected with Styrofoam cups. It's a total mystery to me. I have checked for insects but can't find anything. I live in Las Vegas. We have cold winters but they were protected with frost cloth and the coldest we have had so far was 25 F. for a night . The average being around 32 F. - 34 F.
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Dear Max,
Sorry for the slow answer and thanks for the picture. i wanted to show it to some folks that are more familiar with the big plants but we came to this consensus and hope it helps.
It looks like what we would call "environmental damage". While it can tolerate outdoor conditions in Las Vegas, it isn't always happy with those conditions. As a result, parts of the tissue dies and scars. With higher humidity, the spots would rot, but since it is dry there, they just scab over without killing the plant.
If you were to survey plants in habitat - especially near the extremes of their range, you would find a lot of "ugly" plants that we are not used to in cultivation. It's a hard world out there and cactus like this with relatively "soft" epidermis tend to show signs of dealing with it.
So I guess I'm skirting around an exact cause, but there isn't really a way to pinpoint it. Markings like this are to be expected in an outdoor plant where conditions may be tolerable, but aren't exactly ideal.
Hope that helps.
Maureen (with the help and agreement of the editor of the CactusGuide.com, Daiv, which is a terrific site.
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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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