Cactus repotting best practices

[andy_e]

I'm in the process of switching all my C&S from organic-based soils to a mineral-based mix of crushed granite and screened turface. What do you recommend in terms of how long to wait before watering, and how often to water after that in order to help the roots get established in their new home?

I have this process down cold for succulents but I'm less experienced with repotting cacti. I just noticed last night that a notocactus I did a month ago was loose in the pot and when I gently pulled it from the pot, I found that it had lost all its roots. I'd guess too much water. I have a few more cacti that I have to do and I'm now a little gun shy so your advice is greatly appreciated.

[cactushobbyman]

For every grower you'll find a different soil recipe. I like at least one in five parts potting soil. My hot weather I can use a heavier soil. Unlike most, my soil is damp when I transplant. I find for my area if I leave the transplanted cactus too dry for too long, it will loose the roots. In SF, you may want to have your soil just wet enough to keep the dust down and maybe water in one week.

[7george]

Losing roots can happen for different reasons. Find what causes it in your case. But if soil stays wet for a long time this might be the reason.

You can first transfer just a part of the collection to mineral mix. Observe the plants and water it regarding their needs. I wait for my plants to shrink and soften little bit before next watering, some of them change the skin color to green-grayish when get dehydrated as well. There is not fixed time for watering cause pot size, sun exposure and cactus size, root density vary considerably. Most of my soil mix contains 0 to 20% organic matter and I still use inorganic fertilizers in the water.