After a wet summer i have had some terrible issues with my TB and root rot but the Pachinoi are growing like gangbusters. Do I need a sandier soil?

Dang this hits home. I had to chop a bridgesii yesterday because the roots were rotting.
Recently in my area, cold morning fogs have been lingering a bit longer than usual.
Re-potting with sandy soil and perlite would probably help.
I am planning on not watering my cactus anymore this year.
The rains should return in a month or two.

Not for me. My bridgesii is fine, in dry or wet summers, as well as the usual wet winters. The only part that rots is the tips when they get frosted.

I haven't lost any Bridgesii to root rot and they've been through a couple of very wet Summers. I use about a 40/30/30 mix of organic potting soil, coarse perlite and coarse sand. When I'm out of sand I mix the potting soil and perlite about 60/40.

Bridgesii seem to do best with lower humidity and drier conditions compared to Pachanoi. OP you're going to have to improve the drainage in that soil mix and maybe move the bridgesii to a location that is somewhat protected from the rain if possible. I have little experience with growing plants in containers, but I believe perlite is commonly added to soil to improve drainage. I've heard that sand is not the best to use because it compacts down and can create more problems than it solves, although YMMV. Gravel is commonly used as an ammendment to improve drainage in the ground, but I'm not sure about using it in containers. Maybe more people will chime in with advice on the soil ammendments that work best for them.

Also, if your conditions are wet and rot is a problem then hopefully you are not watering the cacti. They really want to dry out between waterings, especially bridgesii. I wish you all the best OP.

I woudn't use sand, but rather pumice. First 3cm larger pumice (10-16mm) for drainage, then mix of equal parts of
- small pumice (3-6mm)
- high quality sieved compost without any larger pieces
- regular soil.

I have tried using just 50/50 mix of pumice and compost and it works very good too. But it likely depends on your compost as well.

Protection from rain is very good idea. It is much easier to provide accurate amounts of water and fertilization is easier too.

Yes, bridgesii seem more prone to rot, in general not just the roots, than the other species are. This is just based on anecdotes and watching my own cacti but I believe it's true.

I've been using about 15 percent coco coir, 15 percent peat moss , 10 percent compost and amendments ( alfalfa meal, kelp meal, bone ,meal, azomite, worm castings, malt barley and wheat seed and more recently chicken manure and crab and lobster shells) and the remaining 60ish percent is pumice and/or perlite... Depending on what I have and how much money I have; pumice is way more expensive for me. Some people are able to find it locally in which case it may well be close to the same price or maybe even cheaper than perlite.. From everything I've heard pumice is preferred for aeration , as opposed to perlite or some form of gravel etc, and from what I can tell it is definitely superior ...


I'm not sure on the exact ratios and what you'll want to use yourself will vary and depend on your climate and how much water they are getting etc.

i had the same group catch root rot over and over and over again.

My other cacti are totally fine though....

They are, while T. pachanoi is one of the most forgiving cacti a person can grow. I believe pumice is preferred over perlite for cactus/succulent grow mixes if you want to add more drainage. Ultimately, where climates dictate indoor winter hibernation for cacti, the most critical time period for drying out the soil is fall/late fall or the weeks before you're going to move them indoors into a cool, dark or dimly lit area to stop growth (so as to avoid etoliation and ugly cacti). If they come indoors with wet/moist soil, they've got a good chance of dying due to root rot. Think about moving them to a sunny spot under roof cover or building a makeshift rain hood over them with pvp pipe and plastic sheeting as fall sets in so that you can prevent fall showers from getting the soil wetter than you want.

Thx for the good info everyone. I will try the pumice. I had used maybe more sand than i should have. I have quite a lot of rootbound cacti to deal with in the spring. All are safely dormant now just waiting and waiting...