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I was always under the impression that all cacti prefer acidic soil. I am now learning that there are some cacti that actually prefer alkaline soil. Does anyone know of a list of the cacti species which prefer alkaline soil? And what or how do you raise up the alkalinity of the soil?

The question has always been as to whether they prefer alkaline soil or simply tolerate it? Some claim they grow on alkane rocks or soil because they can since competition from faster growing plants in more favourable soils would crowd them out. Therefore the soil they grow on is not the one that provides optimum growth.

I remember a botanist claiming cacti on alkaline rocks only grew when acid rain fell and stopped growing when the rocks gradually turned the water alkaline. Obviously with a family as large as the Cactaceae some will be more tolerant of acid or alkaline soils. However I do not know of any controlled experiments to see which PH suits them best since our plants are slow growers and also often slow to die from adverse PH therefore definitive tests may take a few years.

See:-

viewtopic.php?t=42032#:~:text=%2590%20o ... lkaliation.

https://www.rrm.me.uk/Cacti/Cactus%20an ... linity.pdf

Scroll down link for text and tables:

https://www.researchgate.net/publicatio ... y_A_Review

Thank you, Dave W, for the information. It was very interesting and helpful.

Kelly