Cactus rot is a super common problem, and one of the main causes of cactus death. But just because your cactus is rotting doesn’t mean you can’t save it. In this post, I talk about the causes and symptoms, answer all of your questions, and give you step-by-step instructions for how to save a cactus from rot.
Rot can start anywhere on a cactus plant. It could start from the bottom and spread up the plant. It could start at the top and spread down. Or it could start anywhere in between.
No matter which parts of a cactus plant are rotting, there are steps you can take to save your plant. The steps are a bit different depending on where it’s rotting.
But don’t worry, I’ll give all the details for saving a rotting cactus in this post! Here’s what’s included…
Table of Contents
Why Is My Cactus Turning Brown At The Top?
When a cactus starts to turn brown and mushy at the top, it likely has something called tip rot (aka cactus stem rot).
Basically that means that your cactus is rotting. Cactus stem rot will spread quickly if nothing is done about it.
Once a cactus starts rotting top down, it won’t stop. It will continue to spread all way down the entire stem, and will eventually kill the plant.
So, once you discover cactus tip rot, it’s important to act fast in order to save the plant.
Why Is My Cactus Rotting Top Down?
There are a few things that can cause a cactus to rot from the top down. Cactus rot is caused by either fungus, disease or water getting into an open wound on the plant.
If a cactus is damaged in any way, it is vulnerable to being infected with disease or fungus spores. It’s also very common for water to settle into the wound, causing the plant to rot from the inside out.
The damage could have been caused by anything, including bugs or animals feeding on the plant. Someone could have brushed up against it, the plant could have tipped over, or maybe something fell on it.
You may never know the exact cause, so don’t beat yourself up about it.
The good news is that the steps for saving a rotting cactus are the same no matter how the it started in the first place. Below I will show you how to stop cactus rot from spreading so you can save your cactus.
How To Save A Rotting Cactus
Once a cactus starts rotting, all the rot must be pruned off in order to save the plant. If it’s not completely removed, it will continue to spread, eventually killing your cactus. And cactus rot spreads very quickly.
You don’t want to end up with a dead cactus plant, so you’ll definitely want to act fast.
The steps for saving your cactus depend on where it’s rotting. So first I will show you the steps for how to save a cactus that is rotting top down.
Then, in the section below that, I’ll talk about how to save a cactus that’s rotting from the bottom up.
Related Post: How To Water A CactusPlant
How To Save A Cactus Rotting Top Down
Cactus tip rot can be very deceiving. You may notice small brown spots on a cactus and think that it’s just a tiny bit of rot.
Then once you start removing the bad spots, you realize that it’s much, much worse on the inside than it looked on the outside.
So first, take a moment to prepare yourself for what you may find once you start cutting. Ready? Ok, follow these steps to remove cactus stem rot…
Step 1: Choose your pruning tool – You can use a sharp knife or pruning shears to remove the rot. If your cactus is really thick, then I recommend using a sharp knife.
Otherwise, for small plants with thin stems, precision pruners or bonsai shears would work great. Just make sure they’re super sharp so the cactus stem won’t be crushed.
Step 2: Clean your cutting tool (do NOT skip this step!) – Whatever tool you choose to use, it’s extremely important that it’s clean and sterile before you make any cuts.
Using a clean pruning tool will help prevent the spread of disease and fungus spores. You can simply wash your pruning shears or knife with soap and water, and then dry it before starting.
I also recommend washing and drying it again between each cut. You could also dip it in rubbing alcohol to sterilize it.
Step 3: Remove cactus stem rot in layers – It’s best to prune off the rot in layers so you’re sure that all of it has been removed.
Here you can see that the center of the healthy looking portion of my cactus plant still has rot on the inside. So we have to keep going…
Step 4: Continue removing layers until all signs of rot are gone – As you work your way down pruning off layers of the plant, the rot will get thinner and thinner.
But remember, even a tiny bit of rot can continue to spread. So be sure you remove all signs of brown, soft and mushy cactus material until there are no more signs of rot left on the plant.
If your cactus is an outdoor plant, try to make the last cut at an angle so that water won’t settle on top of the wound (which will likely just cause it to rot again).
I would also move the plant to a dry area where it’s protected from rain until the wound has callused over, if possible.
Unfortunately, the rot on my plant was really severe before I noticed that the top was turning brown. I had to cut off over half of the cactus to remove all of it.
As difficult as it was for me to remove a large section of this cactus, I know my plant would be dead in a matter of weeks if I left behind any rot.
Cactus Care Tips After Pruning
If you have to perform this type of surgery on one of your beloved plants, keep an eye on it afterward to make sure it doesn’t continue to rot. If it starts rotting again, follow the same steps above to remove the new rot.
After a couple of days, the wound should callus over, and your cactus will eventually send out new growth near the cut.
I was super sad to have to cut my cactus in half to remove all the rot. But heck, in the end I think it added more character to the plant.
How To Save A Cactus Rotting Bottom Up
Unfortunately, if your cactus is rotting bottom up, or the cactus roots are rotted, then there’s not much you can do to save it.
The best thing to do in this case is to cut off the healthy stem pieces, and propagate the cuttings.
Prune your cactus back in layers as shown in the steps above so you’re sure to get all of the rot off the cuttings. Allow the cutting to dry for several days until the cut end has callused over.
Then dip the stem in rooting hormone and stick it into a sandy cactus soil mix.
Don’t water the soil until you see new growth on the cutting. Depending on the variety you have, it can take several weeks for cactus cuttings to root.
Related Post: How To Make Your Own Cactus Soil Mix (With Recipe!)
Cactus Rot FAQS
Here are answers to some of the most frequently asked questions about troubleshooting common cactus problems. If you can’t find your answer here, go ahead and ask in the comments section below.
Why is my cactus turning black on top?
Because of cactus tip rot. Cactus rot can look black or brown in color.
Why is my cactus turning yellow?
When a cactus starts turning yellow, it’s a sign that it’s probably starting to rot. If only parts of your cactus plant are yellowing, then you can follow the steps above to save it.
However, if the entire thing is yellow, and your cactus is soft and mushy, then you may not be able to save it.
How do you save a dying cactus?
It’s really hard to say how to save a dying cactus without more information. It depends on how it’s dying. Most of the time a cactus will start dying either from tip rot or from bottom rot.
So check the plant carefully to see if you can find any parts that are changing color, or if the cactus feels soft. A soft cactus or a squishy cactus are both signs of rot.
Why did my cactus rot?
As I mentioned above, the main causes of cactus tip rot are either that a fungus or a disease has infected a wound on the plant, or water settled into it.
Cactus bottom rot is usually caused by overwatering. An overwatered cactus doesn’t always start rotting right away, so it might not be obvious that was the cause.
How do you bring a cactus back to life?
Well… that depends on how dead it is. But if the cactus is completely mush and there’s no green left on it at all, then I’m afraid you’re probably not going to be able to bring it back to life.
If, however, there is still a decent amount of healthy growth on the plant, then you might be able to save it by following the steps above.
What causes a cactus to die?
Overwatering is the number one cause of cactus death, especially for potted plants. A consistently overwatered cactus plant will starting rotting at the roots, and eventually work its way from the bottom of the cactus up.
Signs of overwatering cactus plants are difficult to spot though. Many times once the obvious signs show up (cactus turning yellow, black or brown, or a soft and mushy cactus plant), it’s too late to save the plant.
If you’re unsure of how much to water your cactus plant, I recommend getting an inexpensive soil water moisture gauge to help you get it right every time.
Cactus rot can be super frustrating, but it’s not always a death sentence for your plant. Unfortunately, it’s a pretty common problem with cactus plants.
So it’s a good idea to check your plants regularly for signs of rot. And remember, if you ever notice your cactus rotting make sure you act fast in order to save it!
If you struggle to keep your houseplants alive during the long winter months, then my Winter Houseplant Care eBook is for you! It has everything to need to in order grow healthy houseplants that will thrive all year round! Download your copy today!
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Share your tips for saving a rotting cactus in the comments section below.
Heather Bowring says
we live in apartment block and have a columnar cactus outside on street level at our front entrance, which was about 6 feet tall, until some cactus thief passing by, cut it in half and removed the top half for themselves.
Will the cut area on the remaining cactus regrow or rebud?
I do not have a photo at this stage, but will send one in a couple of days.
Cheers
Amy Andrychowicz says
Oh no, that is terrible! Who would so such a thing. 🙁 The good news is that new growth will form around the top of the cut area on your cactus, so it will branch out and keep growing. The only thing I would recommend doing is making sure the cut is at a downward angle so the water doesn’t pool on top, if possible, or it could start rotting. Good luck, I hope it will come back bigger and better than ever!
Darren Kritz says
This guide has been extremely helpful with caring for my three cacti. (all of them are cylindrical species [the ones that grow kinda tall? two have a bunch of ribs and the other has fewer]) I recently repotted all three of them because of dry rot or just signs of aging. I have had these since for well over a decade now. The two small ones are doing just fine and are growing taller, but my big boy is who I worry about. He is one of those tall cylindrical cacti with a dozen or so ribs and small clusters of large spikes. He currently suffers from extensive fungal dry rot and almost no live roots. He spent about 9 years growing in the same tiny plastic seedling pot I bought him in so all his roots were bursting out from the plastic and woven between it. So when I repotted him, I was impatient and just went to town removing the plastic and affected roots. There was quite a lot of healthy roots but they were embedded in the plastic. By the end, he had a single healthy root left. I just crossed my fingers and planted him, and now 4 months later I noticed that he is growing a tiny pup at the fungal dry rot-infested crown! I have no idea what to do now! The dry rot is extensive – to the point that there are large hard, black masses dotted around the cactus from the base to the crown. The area that broke around the surrounding the healthy pup is just a matte pitch black. He is still very green under the gray sunburns he has. (I’ve been able to scrape some of it off as well as it falling off on its own.)
What do I do at this point? Should I just sparsely water my cactus while the tiny healthy pup continues to grow to a size which I can cut off? Could the pup get infected with the rot as well? He’s way too tiny to cut yet. Also, there a few large spikes in the way of the pup, to the point which if I let it keep growing they will probably embed in the pup or the pup will simply push them away/break them. Should I cut these spikes off to make space? And should I even attempt cutting the top of the main cactus off and propagating it? The damage is quite extensive but I’m holding out hope since I have had him for most of my life. I might even give that a shot, scoop out the offending rot as much as I can and coat it in rooting hormone. (The rot is all the way at the crown and bursting through two spots of it.)
Amy Andrychowicz says
The best you can do is leave the baby intact, and hope it matures before the mother plant dies. The rot certainly could end up spreading to the pup, but if it’s not large enough to root on it’s own, then there’s really nothing else you can do but leave it on. You certainly could try taking cuttings of as much of the healthy crown as possible, and rooting that, it certainly is always worth a shot as a last-ditch effort to try to save it. But that will only work for some types, so keep that in mind.
Vicky says
Hi , I’ve just read your article in hopes of saving two cactus, a rather sad story. … my sweet precious daughter in law recently lost her father who she did not really know except by phone and she inherited his two beautiful cactus … they are huge to me .. at least 5 feet in pots … since we had to move them immediately , I lived the shortest distance ( she lives an hour away )we brought them to my house .he was a heavy smoker so they spent about 5 days under my porch outside due to the cigarette odor… we moved them inside and noticed it turning yellow .. now I am going to follow your instructions because we have some tip rot … but the pots still smell terrible.. will it shock them too much to repot them and cut them also ?
Thank you so much for making instructions easy to follow!
Amy Andrychowicz says
So sorry to hear that your cactus plants are turning yellow and have tip rot. I do not recommend repotting them at this point. It’s best to wait until they recover from cutting off the rotting parts before you repot them. If it’s warm enough outside, I would just leave them out there for the summer. Keep them in a shady spot so they don’t get sunburn, and slowly move them into the sun. Just make sure the pots have drainage holes, or they will drown when it rains.
Dusk Pendragon says
Thank you so much for all this info. My family has a small cactus that i believe is just over 30 years old and he’s very important to me for some reason. He’s just always been around. Anyway i don’t know a lot about cactus care, but recently he snapped in two revealing some pretty extensive internal rotting and its worrying me a lot. He’s only a small cactus and we have already cut a large portion of him away but he still has brown mush inside. His skin is still sturdy and a healthy green and his spines are firmly attached, as well as being sturdily rooted in the ground. I don’t know how deep the rot goes and worries me so much. Is it possible to scoop the rot out and he would recover or should I just keep cutting and hope there’s some without rot before I it his roots…
Amy Andrychowicz says
Oh no, so sorry to hear that your cactus is rotting on the inside, that is so frustrating! If I were you, I would try doing exactly what you said. Scoop out all of the rot, and keep your fingers crossed that it will survive. Good luck!
Kellie says
I have an optunia species that had three large paddles from the original paddle. Two of the top paddles were affected by the recent freeze we had and looked like they were rotting at the tops of each paddle. I used a clean knife to remove each paddle from the original paddle, making sure to clean before cutting a new paddle. I then Removed the top half (to include the rotting area) from each removed paddle. I now have my original paddle with a single secondary paddle and then my two removed paddles with the top halves removed. From your experience, is it possible I could save these half paddles and new growth occur? It’s similar to this article but with paddles
Amy Andrychowicz says
Yes, I would definitely try rooting the cactus pads that you cut in half. They are very prolific, and should regrow no problem. It’s certainly worth a try. 🙂
Don Echelberger says
what are the white things attached to the spines of my cactus? does not appear to be mealy bugs or scale. they are only on the spines. I don’t see any ants, so I don’t see how they get there.
Amy Andrychowicz says
Some types of cactus plants are naturally hairy, and some have more on them than others. As long as you’re sure they aren’t bugs, then it’s probably normal for the variety you have.
Margie Holmes says
I have been given a barrel cactus and its black at the bottom to about a quarter of the way up and then brown for another quarter. What can I do to save it. We get a lot of rain here on the coast of NSW Australia. Tks Margaret
Amy Andrychowicz says
Sorry to hear that your barrel cactus is rotting from the bottom up. Unfortunately, I don’t think you can take cuttings of the healthy tissue to propagate. Look for any healthy pups around the base, or any growing out of the top or side of the mother plant that you can separate and pot up. Otherwise, you could certainly could cut the top off and try rooting it as an experiment. But, as I said, I don’t think it will work with a barrel cactus. In the future, make sure it’s in a very fast draining sandy soil, and try putting it in a spot that doesn’t get much rain, or where the soil can stay dry. Good luck!
AZ Desertgirl says
My ten foot tall Pilosocereus has a black flesh fungus. I have followed your helpful instructions pretty much to a t. I’m very concerned because it has three large arms that are supported by this trunk. The stalk appears to be very steady and stable. I removed the needle spikes first, so I could get closer to the base. Black, gooey liquid started to emerge. I thought I was going to be sick!
I live in Phoenix, and we have had horrible extreme heat with drought. I thought I was doing my columnar grouping a favor by watering it a gallon, every other day. But then the monsoons showed up! 3 inches of rain doused my grouping. UGH!
Anyway, I performed surgery on my guy. I removed a lot of very wet, black fresh. I let it dry out for two days, but I need to go back and finish it. The rest is in a harder to reach area. I’m hoping he doesn’t crash down on me. 😉 I need to finish the job, but thinking ahead to how to apply the Sulphur powder.
How would you suggest that I apply the Sulphur powder to the base? I think this is stumping me. I believe natural sunlight will help kill the fungus. Do you believe that to be true?
Thank you for much for your knowledgeable step by step instructions! You are a lifesaver. I’m hoping my surgery to this 10 foot tall cactus can indeed save him.
Please reply on the best way to apply Sulphur powder. Thank you!!
Amy Andrychowicz says
Oh no, I’m so sorry to hear your huge cactus plant has started to rot, that is such a bummer! I’m thrilled to hear that you have been able to follow my instructions and get some healthy cuttings from it, that’s fantastic! Honestly, I have never used sulphur powder before, so I can’t speak from experience. But I do know that there are powder duster tools that you can buy just for this purpose. Check your local home improvement store, garden center, or search online to see if you can pick one up. I think that will make the job much easier for you.
IAN LIM says
Hi, my cactus has been getting dry and brown in patches at the bottom. I’m not sure how to save it 🙁 Do you have any tips?
Amy Andrychowicz says
Check to see if the brown patches on your cactus are soft or mushy. If they are, then it’s rotting, and the only way to save it is to follow the instructions above to take cuttings. Otherwise, if the spots are dry and the cactus has new growth, then it may recover. Just be sure to water very, very sparingly. Let the soil get completely dry, and then give it a tiny bit of water. The soil should never be wet. Good luck!
IAN LIM says
Thank you! 🙂 The brown patches are dry, so I’m watering it when the soil is almost sandy and dry.
Amy Andrychowicz says
You’re welcome!
Bryon Gibson says
My moon cactus has a black spot on the side of the round top (my cactus has a pink round top & a green bottom it splits 3 ways naturally) and the bottom is so weak that my cactus has fallen over… I’m afraid to ask but I’m going to any way… Is it to late to save my cactus ?!
Amy Andrychowicz says
Oh boy, if the whole thing has fallen over and your moon cactus is soft and rotted, then I’m afraid it may be too late. 🙁