Just too tried out?

[Snailkat]

Hi. I am new here. I have a cactus that a friend gave me 3-4 years ago. I don't know what kind it is but from searching pictures, I guess some sort of mammilaria? I have repotted once in the time I've had it. It has done fairly well up until about this past summer when I began noticing it was turning brown at the bottom. I thought it was just dirt and moved it around in the pot a little, but it doesn't brush off--I think it's dying. The spines are shriveling and white hairs are thinning out. I have included a flowering picture when it was new and maybe you can see a little of the dusty brown at the bottom in the other pictures (current). I lifted it out of the pot and found the roots are all compacted. I used a commercially made cactus mix soil, but maybe that's not the best. ?? I don't know what to do. So here are my questions:
-How can I safely free the roots up without hurting the plant?
-And should I repot at this time in a different soil?

[greenknight]

Common problem, see this link: garden centre plants in peat for how to fix it. That's pinned at the top of the Cultivation forum because it's such a widespread problem. The good news is you can probably revive it.

You have the right idea about what the problem is - when that peat gets dried out it doesn't easily re-moisten. Yes, you need to get the roots free of that stuff. Some of the roots may have died, those should be removed.

You're also right about the ID, I believe that's Mammillaria plumosa.

[greenknight]

On further thought, specific answers to your questions:

-You're going to damage some roots in the process of cleaning out that peat, but that's not important - it will grow new ones. Just don't water it until it has time for the roots to heal, to avoid rot.

-I think I would repot it now. You may need to move it to a smaller pot, depending on how many roots you end up with - the pot should be only a little larger than the root ball. In a month or so you might give it a little water, but don't give it a full watering until spring.

[Snailkat]

Hey, thanks so much! I'll try it today. I live in a tiny town so I'm not sure what I'll drum up for the grit, but I'll do my best. You said not to water until the roots have time to heal--and you think that'll be about a month, is that right?

[greenknight]

Since we're getting into the dormant season in the Northern Hemisphere, you don't want to give much water this time of year anyway. During the growing season, I would wait only a couple weeks before giving it water.

[hegar]

Your plant also seems to be a bit etiolated, which indicates, that it does not receive enough light. The body then becomes more lanky and the plant will appear less compact. The tubercles elongate too. This is why you are now able to see the green stem. Your goal should be to keep your cactus as compact as possible, with a dense cover of those beautiful white spines.
A different type of growing medium would also be helpful, in order to achieve that goal. Also, keep in mind, that you want to fertilize your plant with for example Miracle Grow fertilizer at 1/2 to 1/3 the recommended dosage. Purchase the kind of fertilizer that does have a large second number and a small first one. The first number indicates the macronutrient Nitrogen (N), which influences growth above all, the second number gives the amount of Phosphorus (P) present in the fertilizer. That component is vital for flower and fruit production. The last number stands for Potassium (K). It too is important for proper plant growth.

Harald

[greenknight]

I agree, it does need better light. Not important right now, but next Spring when it starts into growth.

I wouldn't worry about fertilizing it for the first year after you repot it, if the mix you use contains any nutrients. In subsequent years you can fertilize lightly.

[Snailkat]

Thanks guys, you all are very helpful!