I bought a pair of San Pedro Cacti from Home Depot during the past summer. I've been watering them pretty regularly according to included instructions. The problem is I don't have an indoor grow light so I've been putting them outside on sunny winter days. It is my understanding that they tolerate cold fine. I forgot to take them back in one night and found them the next morning. The temperature dropped down to 0°F . I brought them in and fed them warm water. I have an electric space heater which I used to gradually warm them.
Once warmed, they are now squishy and soft to the touch. They seem to be "sweating" out their insides and shriveling. The new sprout rapidly turned a dark brown.
I'm seeking advice on how to proceed... here are some pics :

Eh... It is a sad sight. This happened to mine not too long ago, looked very similar: discoloration, soft and squishy, and oozing cactus liquid, seemingly overnight when it was bitter cold. Mine unfortunately were too far gone to be saved, but there is always hope! I'm no cactus expert by any means, but I would suggest cutting off the top part, as much of the dead part as possible and let it callous over. New pups will sprout here if the stalk and roots have not been too damaged by the frost. You can save the parts you cut off and extract from them.

Give them love and hope for the best!

when I had this happen once before, the issue was caused by problems with the soil and over-watering, I removed the black areas of the cactus, changed the soil, (be sure you are using soil which drains very well and does not hold water) and gave the cactus less water, and it fully recovered...

I think the issue has more to do with poor draining soil, over watering, and contaminants in the soil than it has to do with being cold...but I could be wrong.

-eg

I never had any problems until I left it out in the cold. Maybe it froze and now it is thawing? I removed the black sprout

Yeah, trichos generally don't tolerate freezing that well. If they are bone dry (like not watered since Fall), they can handle around freezing for short bursts, but 0 is way too cold.

If the whole thing is squishy, I'd make a tea. If there are any parts that are still hard, you might be try cutting so only that part remains and try to reroot and grow.

If you don't have indoor lights for cacti, you can just stop watering in the Fall and put them somewhere out of the way indoors until Spring. They won't really grow over winter, but they will hang out for long periods until they can start growing again.

Yeah, I figured that I could have been incorrect on this one, in my case the soil had become thick and poor draining, a build up of excess water and a moldy wash cloth sitting under the holed pot contaminated the roots, causing the top of a cactus and it's pup to turn into black "mush", so I cleaned the area, I removed the contaminated wash cloth, removed the old soil, replacing it with fresh, clean, well draining soil, and allowed it time to heal and the cactus fully recovered....

...people will see the very top of the cactus turn black, and never suspect the cause was the soil or contaminants on the roots.

Again, in your situation I may be incorrect, I've never had experiance with a cacti freezing.

-eg

Yeah the drainage seems fine.
They are still rather firm from the base up until the middle, then they get soft... not totally limp but soft enough to squeeze a bit..
They're not really heavily discolored.. it just looks like they "lost weight" and mass after they thawed... like they shrunk and became squishy.
I'm going to keep them indoors and wait to see if they worsen,
I don't want to amputate them yet. I think they've been through enough lol.
Thank you all so much for the input!

If it's cold enough to get to 0 f, DON'T WATER YOUR CACTUS!!!!!AT ALL !!! This is the biggest mistake I see people make....it's a cactus, not a flower they don't need a lot of water. Especially in winter when they aren't growing much anyway, don't water. Watering during winter you are risking root rot severly, and it's better for plants to not water until marchish. Cactus will start to shrivel if they need water, and are well cactus they do t need water. It won't make them grow super fast, and will just increase the risk of root rot.


Now to your plants. If they are soft and oozing juice then the cell walls of the plant have been broke and rot is starting to form...it will slowing take over the entire area that is soft and then it will kill your whole plant, fairly quickly (2-3 days).

So you kind of need to act fast. I would cut down until there is no more soft tissue. It doesn't have to turn black it can be green, cactus should not ever be soft and oozing. This is dead plant parts. You need to cut it off.

Just being soft and squishy it could be okay, but if it's oozing, no way.

Anyways soft squishy, oozing, and shrunk means dead plant material and you need to cut that stuff off. It will eventually kill the plant.

Hello lsDxMdmaddicThc...

Unfortunately, they took a serious and likely irreveraible hit. The soft oozing parts need to be removed and hopefully the base will survive and push out new growth later on...

As UncleSyd said (and might i add you are spot on with the advice) cactus should not be amd really need to be watered at all (or only very little around the outer rim of the pot) in the winter season.. they sense the change of daylight hours outside and will naturally want to go into a dormant state. They can happily survive in a window during winter time with very littlr watering.

The damage is done and it doesnt look good unfortunately. Cut the soft parts off (im guessing the majority of the cactus) and DONT WATER IT.

So I cut off the tip of the tall one and It doesn't seem to be rotting, however it is extremely squishy. There is hardly any firmness except in the outer skin. I also noticed a white mold growing at the base of the cacti. Should I cut more off? How should I treat the mold... would a mist of hydrogen peroxide suffice or should I swap soil entirely?
Will the dead portions be safe to take as a sacrament?
Update. I cut it down to the base.
It is oozing clear gel and it is soft all the way down to the base...

Well, it doesnt sound great.. rot likely hasnt set in yet but thats next... if its squishy down the the base, the root system likely took a hit a hit as well. I hate to to be the bearer pf bad news bit it doesnt sound good. The cacti seems to have been well frozen breaking down most of the cell walls... imminent death.
If you want to treat it, sulfur might be best.

The dead parts are absolutely usable still... turn a negative into a postive.
Good luck mate..

Sulfur for the mold or for the cacti?
And I wonder if it'll give me a bad experience as revenge...
I feel like I've failed the mescaline gods...

Sulfur would treat the mould. If the cacti are still firm lower down then trim back the squishy part until firm flesh is reached. This should be apparent visually as well. Save the trimmings for an extraction and dust the cut on the surviving cactus with the sulfur.