My cactus appears to be dying and I cannot figure out why. I don't even know what kind of cactus it is--it was labeled as a Christmas Cactus but it definitely is not. It is nearly a foot tall with long spines that come out as little tripod formations, and usually it has long, narrow leaves sprouting out of the top. A few days ago I noticed that all of its leaves had shriveled and turned brown and it wasn't replacing them. Upon further inspection I found that halfway up it had a hollow, squishy spot, covering maybe an inch at most. I did some research into cactus diseases and parasites today but didn't find anything matching this description. The closest I can guess is root rot, but every source I've read says that it starts at the bottom and works its way up, and the base seems just as strong as its ever been. The whole thing does look a bit yellow, but it has never looked all that green to begin with, so I don't know that anything has changed. I know that it hasn't gotten much sunlight, given my window situation (college dorms are hit-or-miss when it comes to nice plant spaces). If I didn't know better I would think something had laid eggs in its middle and that larvae were eating it from the outside, but I haven't found any information about insects that might do that (and my room appears bug-free, and there are no other succulents from which he might have caught it). Should I plan for the worst and try saving the healthy bits, or is there a simpler explanation?
I'm not sure what's wrong with your plant for sure, could have been over-watered at some point, even before you brought it home, possibly a disease, or pest problem. You might want to ck the roots.... If the top part is solid, you might have to do some surgery to save it by cutting the top part above the soft spot, letting the end completely dry and re-rooting it. Could what you have possibly be a Madagascar Palm? (pachypodium lamerei) They do like to have lots of light.
sounds like it's some kind of euphorbia - some they look similiar to cacti (have spikies) except they have leaves (which cacti don't). could be damage that is now presenting as rot. has the plant been knocked over? can you post a pic of it? the plant as well as a close-up of the bad spot. as for the rotting spot, does it go all the way around? if so, i'd lop off the top piece (make sure you are above the soft/rotted area when you cut), allow the cut end to callous over for a week or two and the pot it up in dry soil medium and allow it to sit in the dry stuff for a week or two and then lightly water. and continue to lightly water every few weeks.
Here are some pictures. I tried to take a picture of the soft spot but it doesn't look any different than the surrounding healthy parts. The second picture is of the root ball. I have had it for several years now so if it was overwatered it was certainly my fault. I am not sure what the roots should look like, but they didn't seem obviously bad to me. They are sort of tough and dry and woody. One part of the root ball looks like a continuation of the cactus--it's a dry, hard stump of cactus tissue, or so it seems to me. I tried poking at it a bit and managed to pull off a small bit of the tough skin--the inside was a darker brown and slightly damp. The top part is flexible, but not squishy. I think it has always been this flexible, it has never been completely rigid like the base of the plant. I also do not think it is a Madagascar Palm, or if it is it is a very skinny version of one. :) Maybe the picture will help identify it? The plant has indeed been knocked over, although not recently. The last time was this fall when there was a wind storm. It has never been very stable in its pot, and the roots it forms never seem to anchor it well. The bad spot does not go all the way around but it does seem to be very deep. On the other side of the bad spot it is still firm, but when I press the bad spot it sinks at least to the middle of the plant. Do you have any tips for how to go about cutting it? The best knife I have at the moment is a large pocket knife, so hopefully that would be enough to do it. Should I try to leave the end in sunlight or try to dry it out with heat? Also, what would be a good way to keep the blade clean? I have heard that people use alcohol--would hydrogen peroxide work (making sure all of it was off the blade before touching the plant with it, since I think there might be a possibility of it rupturing healthy cells the same way it does in humans)? What heating the blade with a flame work? EDIT: I went ahead and did some cactus surgery tonight. It was rotten all the way through, had a strange smell and it was foamy and puffy on the inside, the skin had just stayed tough in some places. I saved maybe the top half inch of it, but even this seemed slightly spongy on the inside. I'll let it dry for a week or two and see if it's still got some life in it. I suspect that I overwatered it over the winter, poor thing.
Sorry to hear about your plant. If you think you might be able to save the top (5"-7" of it if it looks at all healthy, it wouldn't hurt to try.....Let the cut end callus over first which could take a week or so, then don't water for at least a week after planting. I still believe what you had was a Madagascar Palm (pachypodium lamerei) Here's mine. The first photo wasn't all that great, too much background and a hanging plant above, but you can at least see some of the long thin leaves at the top. Note, the spines are in three's.
