Hi! So I’m trying to save the top half of a very small cactus. I’m not very optimistic because I had to cut off a large portion, and it’s not an easily-propagatable part (like a pad). The bottom half died because it had been planted in peat soil, and it never crossed my mind that the seller could have used the wrong kind of soil. I think the bottom has scabbed over, but I’m worried because some of the areoles are turning grey. The number of grey areoles has increased since I removed the cactus bottom (about two weeks ago) but the other half of the cactus looks perfectly green. The cactus overall and grey areoles are surprisingly firm, and I cut off a few of the grey spots and the inside still looks green (not rotted).

I have a couple questions about this:
1. Is this greying is normal/is it part of the healing process?
2. Will the cactus recover from this?
3. If it can recover, how long will it take for the cactus to put out roots? (How long should I wait before calling it quits?)
4. How should I care for it? Should I water it more frequently than a healthy cactus? Should I set it on top of soil?

Thanks in advance!

some of the areoles are turning grey
(bottom of the cactus)

Not sure if it is part of the healing process, but the cactus has no roots any more so no ability to provide nutrients, so it is likely to start deteriorating. Given that you find healthy flesh below the grey areoles it might be OK, but from he bottom cut, it does look like that side of the cactus while dry was affected by the rot a bit.

The cactus might recover from this, but I suspect luck will have to be involved as the remaining piece is so small. It means it has very little stored nutrients to tide it over as it develops new roots - if it will develop new roots at all.

Who knows how long it will take to put out roots. Could be quick, could never happen. Put it on top of soil, press it down a bit.

DO NOT WATER

As said above, the cactus has no roots, so the water is not going to help it at all. Really no need to start watering until the cactus has rooted.

I think it is worth a try, but be prepared for the worst, while most cacti root readily from cuttings, it usually requires a significant cutting for it to survive the period where it is not getting any new nutrients and is hopefully working on making new roots.

Good luck!

mcvansoest is right. The top half of a cactus is hard to re-root under the best circumstances. I have successfully re-rooted plants but have also been unsuccessful.

Your little plant looks like you did not get rid of all the rot. And it is way too small to withstand months of being rootless and unable to absorb moisture. With cactus, the bigger the piece the better the success.

Here are two I re-rooted. The first is a crested Echinopsis that has rotted every couple of years for the last 7 or 8 and its rotting again. I think I may give up on it (sorry, the photo is blurry). The second is a Ferocactus that re-rooted and has thrived. It took a year to re-root and all that time, it just sat on a pot of dry dirt. Both were about 6 inches across.

Thank you both so much! It seems to have rotted more, so I'm not sure if it's worth saving.

They are always worth saving but (reality check) not always savable.