Wednesday, July 11, 2012

Rotting cactus update

About six months ago I wrote about a columnar cactus (Cleistocactus straussii) that developed rot and fell over. It had been kept dry in the winter, and I still don’t know what caused the rot.

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I cut off the healthy stem above the rot, disinfected it with isopropyl alcohol and left it to callus over for more than a month.

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However, as you can see in the photo above, there was a suspicious spot remaining above the cut. A few weeks after I had placed the callused stem in a small pot filled with pure pumice, the rot returned.

However, I refused to admit defeat. Once again, I cut away the rot but this time I made the cut a good two inches about the rotten bottom. Then I dipped the cut end in isopropyl alcohol and set it aside in a dry spot in the shade.

For a couple of months, I completely forgot about it. Then, much to my delight, I noticed three roots forming at the bottom—a very good sign.

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I also noticed that there was new growth at the top. See the lighter green area in the next two photos.

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Losing no time, I plopped the stem in a small terra cotta pot partially filled with fast-draining succulent mix (Black Gold is my current favorite) and topped it off with more soil and then a layer of rocks for stability. The pot is now in the shade and will receive just an occasional drink until I see continued growth. Erring on the side of underwatering is always wise with cacti.

With any luck, this Cleistocactus straussii will look like my other specimens in a few years (photo on the left). If I planted it in the ground, it would grow to flowering size in about ten years (photo on the right) but right now I just don’t have the room.

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But I think it looks pretty cool in a pot, too.

14 comments:

  1. Nice save!

    If you don't put it into the ground, what are you going to be posting about in ten years? ;-)

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    1. Easy: If it gets too big, I'll rehome it and start over with a small plant :-).

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  2. That is great! Very informative for people like me who are just starting on cacti. I didn't know alcohol could be used, this is good because it is readily available and there is always several bottles of it at home. -- Bom

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    1. Glad to know I was able to share good information.

      Rubbing alcohol kills microorganisms that might cause rot and dehydrates the cut surface, thereby sealing it faster.

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    2. I usually use antifungal preparations from the garden store or cinnamon powder. Yes, the alcohol should seal the end faster. -- Bom

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  3. What a great story about your persistence and how it paid off! The alcohol thing was new to me, too. Thanks for passing that along.

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  4. I admire your persistence Gerhard in saving the Cactus, and what a happy result too!

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  5. Wow...you can dip a cactus in alcohol and not kill / dessicate it?

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    1. You quickly dip the freshly cut surface in it to disinfect and desiccate it. I also use rubbing alcohol in a spray bottle against mealy bugs and against cochineal scale insects on opuntias.

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  6. I have a question regarding don't put it in a large pot. What about when you plant it in the ground? How is that different? They thrive in the ground.

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    1. Planting it in the ground is different in that any excess water would either drain away or be absorbed by the soil near the plant. A pot is a closed environment; when the plant has no roots, the soil might stay too moist for too long, especially in a pot that's much larger than the plant, causing more rot.

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  7. I just preformed this surgery on my cactus thanks to this post. Thank you so much for posting it. I've had this cactus for 13 years and don't want to lose it. Now all there is to do is wait and hope a nice callus forms over the next few weeks.

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  8. Hi, I just read this post of yours as I have been struggling to find information on saving a cactus that has become a victim on stem rot. 2 days ago, I made a cut like you did in this video (albeit only 1 inch from the rotted edge) and left the cut end to dry after dipping it into isopropyl alcohol. The cut end looked green and healthy but today it is turning brownish n wrinkly. I'm not sure if this in the process of callousing or if the rot has set in again. Would you mind if I send you a photo of the cut end so that you can give me your diagnosis? Would greatly appreciate it. Is there any way I can send you the photo? Thanks!

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    1. I had the same experience once. Either the knife you used wasn't sterilized entirely or you didn't make the cut high enough on the plant. Simply redo the procedure, and you should be OK.

      You're welcome to send me a photo: musatopia AT gmail.com.

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