Help With Sickly M. Rhodantha

Hello Everyone,

This is my first post to forums and I'm happy that there exists a community devoted to mammillaria. I am new to the world of cactus and am fascinated by the few I currently have.

When I was purchasing a few from a vendor there was a M. Rhodantha that was given to me for free because the vendor said it wasn't doing well. I of course scooped up a free plant but forgot to ask exactly what was wrong with it. Here is a picture of it.



To me it seems like it is just dried out? I'm not sure why it is also super fuzzy underneath the prickers.

Can anyone help me figure out what is wrong with it and how I can try and rescue it? It looks like it was flowering at one point but they are all withered now.

Thank you in advance!

It's a little difficult to see detail from your photo, but let me make a start.
First thing I'd do is to unpot it, and get rid of all the existing compost so you can see the roots and the neck of the plant. Check the roots and the body of the plant for bugs. Most common is mealy bug mite.If there are some.then use an insecticide to kill them.
Check the roots and remove any dead bits. They and the neck of the plant should look healthy and be just a bit spongy, with no rot or not dried and hard. Rot can be cut off but if the roots are hard and brittle and the neck feels really hard, then it may be too late. But anyway then repot in fresh compost and hope it comes back into growth.
If it doesn't respond then I'd unpot it again, recheck, and either repeat, or more drastically take a sharp knife and cut the roots and neck of the plant off. You can then see clearly if the plant is dried up or if there is sap showing there is life. If alive, let it dry for a week or so and put it on a sandy compost and with luck new roots will grow, but this could take several months.
The fuzz you mention should just be wool, but if it isn't then you could have a bad case of mealy bug, spray it well and several times over a month or more.
Hope this helps, but others might have other suggestions.

Hi Chris,

Thank you for the advice. I went ahead this afternoon and repotted her and took some photos.


When I started to remove the soil I noticed that underneath all the fuzz is a nice green. And that the thickest parts of the wool were in between the areoles, which I believe is where it should be?


The prevalence of the wool is less so around the base making me think that perhaps back where she grew up she got some pretty intense sunlight and developed the wool extra thick for protection.

In regards to the base and the roots, do they look alright? I'm sure there is no rot present, but I'm not sure what otherwise healthy roots would look like?

I also spent some time plucking out the dead flower buds and noticed that where they were coming from on the cactus surface was extra white. Now that this cactus is in a region with likely less sunlight than where it grew up should I try to remove the wool, or will this dissipate with time? Is there any risk with just leaving the tougher to get dried buds where they are? I'm worried it might be a place rot could develop if not removed.

Thanks again for all the help! If anything else this is helping me understand what healthy vs. unhealthy cacti parts look like.

Roots look ok to me but the mix looks like it was a bit lean on ''substance'' and the plant possibly somewhat starved for quite a while. I have just repotted about 100 plants of various genera which were over due so this is very fresh in my mind! In this case I would trim off half of the roots and let dry for a while (depends on your local humidity and temps) then repot into a nice fresh nutritious mix and start feeding during your coming summer. I think you will find it gives the plant a kick-start.