Help for my rotting Mammillaria Theresae

[Not_an_Expert]

Hi All,

I had a m. theresae that was healthy for the first few weeks, but took a sudden turn about one week ago. It looks like it is rotting. Franj posted her beautiful m. theresae blooms, and I am hoping someone can tell me what I am doing wrong.

I currently use a grow light which is on for between 15 and 18 hours per day. I have been watering it once per week.

Here are some pics of the plant.

First, what the it looked like on July 10th:


And what the plant looks like today:


Any would be greatly appreciated! I think this is a gorgeous species, and I would hate to lose it.

Tim

[iann]

Is it rot? Soft and mushy? Always hard to be sure from a photo. Lets assume it is.

Get it out of the pot and see what you have. It needs to be thoroughly dried out anyway so the soil has to go. A rotting cactus can sometimes be saved just by keeping it completely dry, but rot like this in the body tends to take over the whole plant very quickly, especially when it is a nice lush cultivated specimen.

So, take a very sharp knife and start cutting. Remove all the rot. Clean the knife and remove a bit more. Dust with sulphur or some equivalent broad spectrum anti-fungal. Leave to dry for several days or up to a couple of weeks in a humid climate. In the shade, the plant is living on reserves now. Once the wounds are thoroughly callused over, reroot or repot and leaves dry for another week or two.

I wouldn't bet on this plant surviving, it is small. If a large chunk of the root is intact then you'll get something, maybe a bunch of pups next year.

[DieTer-Xz]

Ian is exactly right. But let me ask you something. You're not an expert. Mammillaria theresae is an extremely rot prone species, especially on its own roots. You gave it too much water, not enough real sun, a bad substrate, and a too large pot (it seems). Why did you buy it in the first place? Were you aware of the difficulties in growing this species? And although I suggest you do try to save it, you're probably too late. You're using a clay pot if I can see it right. If it would have been in a plastic one, it would have been dead.

[Not_an_Expert]

Thanks for the step by step advice Ian, I will do my best.

DieTer, thanks for taking interest, here some answers for you.

Why this plant? I think it is unique and attractive.

Was I aware of the difficulties? Yes, or at least I thought so, and I proceeded regardless.

In terms of your other observations/accusations:
1) I watered it once per week, which is what I thought other m. theresae owners were doing as well.

2) It was my understanding from this forum that cacti can successfully grow with adequate amounts of artificial light.

3) I used commercial cactus soil. No, I didn’t make mix my own, as many others here do. Had I thought that nothing less than a hand made mix would suffice, I wouldn’t have attempted to grow the plant.

4) It is a two inch pot. I realize it looks large in the picture because of the proximity to the camera.

From the tone of your post, I have clearly upset you with my mismanagement of this plant. Naturally, my failure in growing it has been a disappointment for me as well.

You have clearly made a prolific contribution to the site, and I don’t question your authority on the subject. However, I think your nasty response to my request for help detracts from the basic purpose of this forum.

[Bill in SC]

After your explaination, I would say the commercial soil mix might be the problem here. (especially with this species) Most commercial mixes have water retaining vermiculite in them. Also, those mixes are NOT coarse enough to drain freely. When you post these dilemmas, it's always good to have all this info to help figure out the problem.
Bill in SC

[Amy]

Hi there Tim, I'm not an expert either! But I do have some of the more difficult Mamm. species, so I can relate to your frustration. Unfortunately, there is a steep learning curve when it comes to growing the rot-prone species. You often lose a few before you get the hang of it. Don't be discouraged, this is a good opportunity for you to learn what went wrong and how to correct it.

I don't know if you've seen this yet, but there is some good information on this species here: http://www.cactiguide.com/forum/viewtopic.php?t=1025

I recommend that you use a very mineral soil mix with this plant. It looks like almost pure peat that it's in right now. By mineral, I mean lava, pumice, kiln fired clay (aquatic soil), coarse grit and the like. Use very little organic matter for this plant. It looks like you got the pot size right, very small and shallow. You could probably grow this little beauty in almost pure pumice really.

When I water my rot prone Mammillarias, I water them only when they are actively growing, and then only about every 10 days or even longer. I wait for them to show me signs that they are ready for another drink. It's hard to describe how I know this, but I look for subtle cues. Daily observation during the growing season will help you realize what the signals are. No water at all in the winter for this one - it will be dormant and "sleeping" and any water will make it rot. Don't feel sorry for it even if it shrivels, this is normal and it needs to go through this yearly dormancy in order to flower and thrive.

Try again if you lose this one. Err on the side of extreme caution, you won't kill it by underwatering. Also, get it outside if you can, just make sure you acclimatize it gradually so that it doesn't scorch. Just remember that this cactus lives in an arid environment and needs very little water in the first place. Once a week is too much unless you live in the Sonoran Desert. I'm going to send you something that a good friend and very experienced grower sent me a while back that has been very helpful to me.

Again, don't be discouraged. These very beautiful Mamms are worth the effort, and when it flowers for the first time for you, the exhileration will make you forget the pain of losing your first one!

[DieTer-Xz]

You shouldn't take it as an accusation. If I made that impression, I'm really sorry. Remember, this is the part Growing Help, we are trying to help you. It is indeed a unique and attractive plant. You were aware of the difficulties. But you didn't read enough about the species. Otherwise you would have known about it being difficult and you probably wouldn't have bought it.

This upsets me for two reasons:
a. It is still a rare and threatened plant.
b. Most beginning growers are demotivated when they lose one of the most beautiful plants of their collection and that would be a shame.

To answer your answers:
1. Watering should depend on the weather (temperature, air moisture and light), there is no real formula for it. I know an old lady who waters her cacti every day, and they look quite nice, but I'm talking about Echinopsis oxygona, and Opuntia microdasys in a clay pot. She doesn't water them at all in winter. She has more flowers on her E. oxygona than I can ever dream of. But we're talking about M. theresae.
2. That's true, but artificial light can never fully replace real light.
3. Commercial mixes, are, exactly as you write it, commercial. Even the mineral parts in the mix are of a low quality, and there's generally too much peat in it. (Also, a mineral composition tends to let the water drop right through.)
4. Probably so. Could be the picture.

You were asking advice, but shouldn't you have asked for advice or read about it before buying the plant, or right after? Growing cacti is a wonderful and rewarding hobby, but can be sometimes more challenging than anyone would think. Even the most experienced of us sometimes notice that. I think you've learnt that now, probably, but hopefully not, the hard way, as you've possibly lost a nice plant.

Also, I do not, as I really don't have the right to do so, think of myself as an "expert". In my opinion, and then I'm speaking in the name of must of us I think, we just exchange knowledge and experiences.

Then again, I'm sorry for my reaction that may have been a little too harsh. I'm also used to help reptile breeders, and there you have to be harsh to let people know they're not doing the right thing or haven't been reading enough, for example, as they state that their small, cute crocodile has got too large!

Good luck trying to save your plant. Please do not think of me as a naughty person right now, as I really am not .

[cactuspolecat]

G'day Not_an_Expert, sorry to see you going through this with such a lovely plant... I've managed to kill one even though it was grafted, and as a young grower it broke my heart. After thirty years of growing cacti I'm still good at killing them.
Don't be discouraged if you're unable to save it, just try again if you get the chance... what you've learned this time 'round is the sort of stuff that you build your knowledge upon.

Cheers for now, CP

[iann]

I just want to add a little more about the artifical light. I am of the opinion that you can grow anything you want successfully under artificial lights, but it takes considerable effort to provide sufficiently intense light for an adult cactus. Plan on a minimum of 30W of HID or modern fluorescent light per square foot of lit area, properly reflected onto the plants. This should provide roughly 2,500 foot-candles which is way less than direct overhead sunlight but will be maintained constantly all day and every day. I know people who use more than twice this much light. Using a less intense light for more hours per day simply isn't a good longterm substitute.

From your two photos, you can see the mild purple colouring on the first one, which for this species indicates good light levels. In the second photo, there is no hint of purple and the overall appearance is a fairly light green, indicating insufficient light. You should use a light with some blue and a little UV, these are the components that cause changes to the cactus skin. HPS light for example will result in soft overly lush growth.

[Not_an_Expert]

Thanks everyone for all of your helpful advice. I have copied all of the text and saved it on my computer for future reference.

I think I did get in over my head on this one. If I am unable to save this plant, I will hold off on getting another until I am more able to provide the it with real light etcetera. I would love to give it another shot.

In the mean time, I will restrict myself to enjoying the successful theresae photos that get posted on here from time to time.

To DieTer, I can completely understand your frustration. I have been around dogs most of my life, and have plenty of experience training and caring for them. Nothing irks me more that seeing the countless dog owners who do no upfront research and know nothing of caring for animals.

I'm sure my experience with the theresae struck you the same way. I assure you I will be much more careful in the future.

Again, thanks to all!

[templegatejohn]

Hi, take CP's advice and don't let it get you down. We all lose plants, whether we think we are 'experts' or non experts. It is part of the hobby of keeping cacti. I have kept cacti like CP for over 30 years and I cannot grow Melocactus. I know how to do it in theory, but just can't manage it in practice.

I have several Mammillaria theresae plants and they are not easy, most of the ones you find commercially are now grafted because so many on their own roots were lost by enthusiasts. They are nice plants and if you like them and can afford it there is not reason why you should not buy another. Try to get a grafted one and even then keep it in a very porous compost, one that drains very freely and only water when the compost is dry.

John