What has happened to this cactus?

Trouble shoot problems you are having with your cactus.
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Matt_2745
Posts: 1
Joined: Fri Sep 08, 2017 5:29 pm

What has happened to this cactus?

Post by Matt_2745 »

Hi all, my mother recently purchased 3-4 cacti from a local garden centre, but after a month one of them is turning almost black as you can see on the attached photo.

I have tried to look online to see what the causes might be but haven't found anything that seems to match, so my three questions would be:

1) Can this cactus be saved?
2) If not, can the others in the pot that are so far unaffected by saved or will it likely spread?
3) What is happening and how can this be avoided?

Thank you all for your time!
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Aiko
Posts: 2369
Joined: Mon Jan 24, 2011 5:26 pm
Location: the Netherlands

Re: What has happened to this cactus?

Post by Aiko »

If the plant soft (I mean, the dark bit, softer than the green bits)? Have you smelled it, is there a rotting smell? Then the plant is rotting and at the looks of it a gone. I would advice you to remove it, although I don't expect it to be fatal for the other two plants. More dangerous for them is the reason why it rotted. How often do you water the plants? Rot happens easily with overwatering. And the peaty soil the plants are standing in is not helping you there...
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hegar
Posts: 4596
Joined: Mon Jan 23, 2006 4:04 am
Location: El Paso, Texas

Re: What has happened to this cactus?

Post by hegar »

I agree with Aiko's diagnosis. The plant does seem to have a rot problem and is most likely dead. By now probably the half that still looks green on the image has turned blackish in color. If you push against the discolored side, you will most likely notice, that it is rather soft compared to when you do this to one of the other two plants.
I would immediately remove all three plants from the pot and dispose of the dead cactus. As Aiko suggested, I too would replace the growing medium with one that is mostly mineral in nature. You can find some "recipes" (formulations) for good growing media here on the CactiGuide home page. While your potting soil may be OK for "jungle cacti" like Epiphyllum, Schlumbergera, Rhipsalis, etc., it is by most cactus growers' experience too rich in organic matter, when successful cultivation of "desert cacti" is the goal. You will do better with a well-draining, porous growing medium, which does not stay wet for long periods of time.

Harald
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