Maybe you could graft something onto the base? I don't really have good directions for you but there are a lot of videos on grafting cacti on Youtube.

er, sorry, why would I do that? if there's something wrong with the rootstock, how would grafting something on top help?

right now my working hypothesis is cold damage .....its the only thing I've found thus far that seems to match my symptoms. I don't spend a lot of time in the room it was in, but I wouldn't be surprised if it was getting really cold, especially at night. it wasn't a problem before, but after the cut maybe it was much more susceptible/sensitive to lower temps??? idk if that makes sense, but I've moved it to a warmer room and am continuing my search for an answer.....hopefully I find one before I lose the whole thing ð«ð«ð«

Hi there, I don't think there are many choices left if it's still in the same state as you pic other than......I think your plan should be to try again to stop that rot asap by slicing the rooted portion away till you get to clean healthy green tissue and keep it on the warm side where it should dry and callous over else it will continue to track down and you will loose all of it. It may well react by still decaying away, I don't know but as I see it you have no option with it while it's in it's present state. Sterilise your scalpel or whatever first.

Gill UK

No grafting onto to base would make it less likely to rot because it wouldn't be exposed bacteria. Although I've never done it successfully. I've seen it done many times and it can actually make the plant grow faster.

This post was edited by CooperDR on Fri, Jan 30, 15 at 8:57

I don't think its rot, though? Its hatds and dried up, not soft or mushy. Can it still be rot like that?

Meow...... sorry I don't really know.

CooperDR....ahhh yes I take your point, I can see what you meant now with that further explanation as to why it could work. Sorry :)

Gill UK

No prob. Gill. Well I think "rot" could just mean anything. You could just leave a stump too. A new branch may or may not grow off of it. I don't see any hope in not cutting off the unhealthy part.

Yes, drying out can be caused by rot. I had A miserable summer-long mealy bug infestation throughout my yard of succulents. I had to dig up every plant, wash each plant, even wash off the roots. Then use insecticidal soap on the entire plant, an hour later wash the insecticidal soap off each plant. Re-plant in new dirt and quarantine each plant (separate pots). I lost many plants but also kept many, it was heartbreaking. I do not know what you have been through with mealy bugs but it ain't over till the plump succulent sings. In my case the mealy was spreading because I have ants and it was recommended that I must get rid of the ants in order to control the mealy. This was accurate advice. In your case, since I do not know if you have unrooted the plant and looked at the roots and looked to see if there is rot, (not that that is easy to tell), but I am aware that rot can cause dried out leaves. if the stem feels soft or hollow in any areas that is a clue. I just found rot in one stem of a two stemmed jade this morning. I could tell by the softness of the one stem. I broke off the bad stem and most of the roots and stuck the other stem back in the dirt. Who knows if it will survive, since it is not my most important plant and I have bigger fish to fry I thought I'd let the rest try to come back on its own. If it was a prized plant I would have done the full toot cleaning thing all over again. My plants have been fine in temps as low as 35 - 40 degrees. When you say cold, I don't know how cold.

It's the other way around- if the roots dry out then they're nonfunctional. So when you water them they rot.

@ Coop
Thanks for that simple explanation. I've had a couple of succulents that I watered ONCE and they promptly dropped all leaves and appeared to have rotted out within 48 hours -____-

Turned black from the center of the stem on up.

Both of them were in the very dried up desiccated soil mix that they seem to always come in. I thought I'd be safe to water since it was soooo dry. Oops.

@cooperdr

oh okay, i understand now re: grafting. still, at this point, I really don't think it's rot . . . i've moved it to a warmer room and the gray part, which was spreading steadily, has stopped altogether. thanks for your help!!!

@annabchill

i can see how that would be the case for succulents, but this is a cactus that doesn't have leaves . . . the bottom half is completely healthy, green, and solid, while the top is rock-hard, desiccated, and gray, nothing soft whatsoever. and of course, different succulents and cacti are hardy to different temps . . . the particular room this plant was in used to be a porch that was closed up by the previous owners, so it can be quite chilly in the winter, especially with the 9 degree nights we've been having. idk exactly how cold it's been, and it's never been a problem for the other plants i have in there, but right now i'm thinking maybe it was too much for the exposed tissue? idk, just a thought!