Is the discolor end part kinda swishy? Cuz it looks like it's rotting to me. I don't know if any of it is viable but I'm sure others will chime in. Good luck

Yes, it is kind of squishy. What concerns me though is that it did not look like that yesterday, it was still quite green. Thanks!

I only watered it when the soil was dry, but I'm also not the only person in this house. It could be other people were watering it as well thinking it needed more water.

Is there anything I can do about the rot, or is it just done for?

Not sure...see the 2 smaller 'branches' - they are black. Looks like totally rotten. Large piece has that "full-of-water" look; totally saturated with water.
I am not sure what should be done - maybe take it out of that pot, get rid of all soil (shake it off, or even wash off), put it on top of newspaper/paper towels to dry out for few days.
When you take it out, you will be able to see the roots - are there any? are they mushy-rotten?
If any good roots, maybe you can save it.
There are some green parts on top, possibly they can be cut off, let callus & maybe they will root.
How soft is the plant?
Take it out & take few more photos of roots & other side of plant.

Rina

Looks dead to me (beyond hope). Unless I'm mistaken, I believe this particular cactus is prone to rot, especially in the winter.

Planto

Well, I took it out of the pot and carefully brushed off some of the loose dirt and took a picture of the other side with the dirt/roots visible... I'm going to try Rina's suggestion and try to get the rest of the dirt off and cross my fingers in hopes that I could save it.

The black portion is fairly squishy, like... poking the bruised portion of an apple squishy. The rest of it seems relatively firm, but the more yellow portions are a little softer, not entirely sure how to describe it. I'm not a plant expert so I can't say what is or isn't root rot. Once I get the dirt off, I'll get a few more pictures.

It would probably be good to cut off the really squishy part.
If you do, dust the cut with cinnamon (if you have any).
The root in the photo looks pretty good. Get rest of the soil off & see rest of the roots & part of main plant at soil line. Don't put it in full sun, just light & good air flow.
Don't worry about plant sitting there without any soil.

That yellowish part shows you that it is 'water-logged'. The black is rotted I would say (just from what I can see in photo).
You have nothing to loose by trying - it is in pretty bad shape now.
This is what I would try if I was hoping to save the plant.

Succulents should be planted in very well draining mix - if it drains well, it's more difficult to overwater.
Rina

Alright, I managed to get most of the dirt off and got pictures of it on either side and a closeup of the roots.

Reminds me of a failure I had last spring.

I had a quite large plant that was growing beautifully and suddenly some dark squishy areas appeared. I also attributed it to overwatering.

Withholding water didn't help and soon I had to resort to surgery. I wound up with seven or eight cuttings that I put in potting soil and was very careful about water. All of them are growing, and are about the same size as OP photos.

The base plant that I left in the original pot dried up and died. Really tragic, it was one that elicited frequent comments, spectacular, even.

The main thing is, (in my opinion) you have to cut out ALL the black areas, it's like a cancer, this is no time for incremental solutions. LB

that is going to be a tough save! I definitely think you should cut off all mushy parts, plus a little for good measure, then let it all calous. good luck!

Hooo... This is going to be rough... I cut off all the really mushy black parts. The base of it is actually fairly firm, so maybe that can be saved still, and there's a the part at the top where its looking a little dark, but its green above it. I'm hesitant to cut that off since it still has some green, but maybe I could save that good piece and potentially grow something new from it? I haven't worked with cactus cuttings, so I'm not 100% on how to root them properly.

I'm mostly worried that the darker portion below the green is rotting that good little section out, and I also think I may need to cut off the rest if it gets any worse.

Here's a photo of what's left:

I do thank you all for your help, by the way! You're giving me good information for the future.

Good luck with it! So far I've had one succ rotted on me, a semp. But it was a wedding favour and they put it in a glass without draining hole and bunch of dirt and marbles which is basically hell for succulents.. I just wish I repotted it earlier so I could save it..

I hate to be the one that says this is a goner, but I will. "It's a goner". The only thing that is alive is the very green top. If you cut it off, you will probably see that the rot is up in it also aways. One would need to cut more of it away to get that off, and get a stem that shows no discoloration, and then you would be left with too small of a piece to root.

Your original problem was that the dirt was to rich and water retentive and it needed a hole bunch of grit in it to promote quick drainage. I would go to the store and get another and toss this one stop yours and it's suffering. This time repot it in appropriate soil as soon as it gets home and do not water it for a week. settle the new gritty soil by tapping it on the table.

Yeeah... Looking at it today the thing is pretty much dead now, which is a shame, but lessons learned I guess.

Unfortunately I can't simply go back and buy another one as when I went back to where I bought this one, they were out of them and the rest of their cactus collection was looking... Not very well. (Hoorah for Wal-mart garden centers?)

Yeah, I should have repotted the thing when I got it, wasn't exactly thinking of that at the time. Ahwell. I'll have to try again some other time.

Maybe get your cactus from another place. We often bring home problems from the stores.

I'm a few years late here but Home Depot and Lowes carries these rather frequently. From 3 inch pots to big ones in 8 inch pots. I have 3 large ones including a variegated form. I grow them in Miracle Grow Cactus Mix. They should be transplanted into clay pots (with a drainage hole!) so they dry out quicker. Plastic is not a good choice for cactus or succulents. Mine sit outdoors in the summer in full sun. I wait for them to completely dry out and then saturate the soil with plenty of water. Using time release fertilizer works great. In winter find them the brightest spot you can and cut back on the water. As with many houseplants underwatering is better than overwatering.

Mine, purchased a year ago, was doing great, growing and thriving planted in Miracle Grow cactus mix. Until now. Noticed today it’s rotting from the center. Hard to see because it’s so big. I cut off all the green and will let them callous. Maybe some will be saved. Once a month didn’t seem too often in winter, but I guess it was. Sad...

The miracle grow cactus soil is not good by itself. It's too soil-y.

So I need to mix it with...?

Try to find a pumice or large perlite. I buy size 2 (perlite) from an organic gardeningþhydroponic store. At least 50% perlite or pumice

I've had no problems with Miracle-Gro Cactus mix. I use it for all my cactus. I have eastern prickly pear cactus (opuntia humifusa) potted outdoors in it year round here in Ohio. Yes, summer and winter. For my Eve's Needle I bring them in for the winter and give them a little water (repeat little,1ww not saturated) every month or so and they do fine. Light and air circulation are two big factors in watering plants. If either or both are lacking over watering can become an even bigger problem. And get them out of plastic and into terra cotta (brown clay) pots with a drainage hole!

While all this preventive stuff is useful, I think the main thing is that these plants are tricky and they don't self heal without major intervention. For starters, you have to cut out all diseased parts with as much attention to sterile procedures as possible. It may look like you would look with an arm and a leg cut off, but that's what is needed, no time for half measures.

I have one that needed major surgery, it had limited success. I have another in a wall sconce on a wall that hasn't received a nickel's worth of attention in more than a couple years and it is happy, nonetheless, and it just gets rainwater, in regular Miracle Grow.

I have a mental list of fussy plants that I have given up dealing with. I like success stories. And, when you get this particular plant, it doesn't seem to be in some exotic mixture, so why should I play around with the formula, when transplanting?

Growing outdoors makes a big difference when using miracle grow-style mixes. It becomes a big problem indoors in the winter. It just stays wet too long.

If it's staying wet too long using MGCM in the winter then you're watering too much. Any soil mix can. Most all cactus and succulents need very little water during winter months indoors. I keep mine in bright light and water sparingly with no problems. They benifit from good light but don't need much water.

Ok this plant likes very very little water. I have this plant growing in a tiny pot with hydrophobic soil. I water it once a month. And it's still growing new parts to it despite how little care it's getting. I wouldn't allow this plant to be wet for over a couple hours. I had this plant rot after 1 day of being wet. Let it remain wet for a very short period of time.

I put mine outside (full sun exposure) during the summer and pretty much let the rain take care of things while they are actively growing. If there's a long dry spell I completely drench the soil and let them dry out again. During winter they'e mostly dormant.

Best of Luck!

Spider

This has stretched out for a long time, I forgot about it until I received a notice today. My suggestion, referring back to the most recent photos, (and by the way, why all the digging up, bothering the root system, since it's already stressed?)

Anyway, what I would do is cut the topmost green healthy parts and replant. Throw the rest away. Pick your soil mix, put the cuttings in a sunny location and forget about it. Maybe a tablespoon of water after 3-4 weeks.

But, another thing. I have 3 or 4 of these that are doing well after my intervention several years ago. They have never been repotted, & neither has the one hanging on the wall. I think they are happier being in a root bound condition, that and neglect. But all of them were potted in regular Miracle Grow, so I'm kind of indifferent to customizing a sandy mix, but suppose it can't hurt, right? No doubt about it, it's a difficult plant to cultivate. Whatever happened to my original plant, it was magnificent, (at least the size of a basketball) but when it got sick, that's what I did, sliced off the decay and repotted the healthy parts. That was at least 4 years ago and they are still healthy, but none are as nice as the original parent plant. For what it's worth, okay?

El Bee

Hello:

I felt in love with this living organism during a visit to a botanical garden in Chicago. So when I came back home, I ordered one line that came from California to Florida en 7 seven days. When it arrived it was like in fetal position and a few weeks later of being in a pot with excellent drainage it was opened like a manual fan with that beautiful intense green.

A few days ago, I saw it and a little branch that was in contact with the soil get black, exactly the same as in the pictures above, so I searched the problem in the internet and found this page just to realize that immediate action is needed. So I took out the plant from the soil and started cleaning the rotten parts. While doing this I found little white worms in the mushy parts (like 1 mm diameter and 5mm length), maybe they were eating the plant from inside and humidity helps them to develop inside it.

I will let the plant drying three days or one week to let the wounds close, after I will put it in soil again.

I just wanted to share this thoughts with you to see if this is helpful for someone.

Thanks.

I had the same one with the same problem I cut the right out and now I am waiting for it to Calais I saw YouTube video and that’s what they said to do but I am searching to buy a new one because mine was huge and I had it for about three years so upset