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This has been going on for a while (about a year), one of my cacti has turned purple. I've just replanted it after its pot fell and broke (no, it did not spend the year on the ground). What is the cause of this and what should I do about it?

I put the cacti out on the open balcony in the summer and put them on the windowsill for the rest of the year, so the usual temperature they are exposed to is 20-35C (as low as 10C during the night). I water them twice a month during the summer and once a month otherwise with tap water, about 100 ml per plant. The height of the cactus is about 6.5 cm. The cactus in question spends most of its time very close to my other cacti (~10 cm), and some of them don't look too hot, pictures below.

Cactus in question about to be replanted, click to open full image

Section of the offspring, the flesh is green with a white center and has no smell, click to open full image

Neighbouring plants showing possibly related symptoms (The other side of the one on the left is perfectly green), click to open full image

kotekzot
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3 Answers3

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Heaps of sun can turn parts or whole cacti a purple or burgundy hue. When the heat is on and you have cacti in outside pots, the roots and plant can also start getting damaged from overheated roots and frequent watering. Keep them in pots that don't overheat (avoid black plastic) and the media should be coarse but still retain some moisture without soggy bottom.

Chris
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Phosphorus deficiency can turn green plants purple. That would be my suspicion.

Here's a forum post discussing a Christmas cactus that turned purple. They also mention phosphorus, and other things, like temperature, sun, over-watering, under-watering and stuff.

Brōtsyorfuzthrāx
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2

From my personal experience with succulents + cacti, I run into this presentation when my plants are/experience:

  1. too thirsty. Waiting too long between watering can stress out the plants and give them the "hollow" or thin appearance here.
  2. too much light. Cacti can definitely get sunburned! Ensuring that your plants have plenty of time out of direct sunlight + in cool temperatures will likely help.
  3. bacterial rot. If I have alternated overwatering and underwatering for a plant, rot has an opportunity to take hold. There's not much to be done for rot in succulents, in my experience. If there's a funky smell from your plants, I think rot is pretty likely.

General tips for succulent care:

  • They grow quickly, and you might want to deadhead or separate individual plants as they crowd together.
  • Waterlogged soil should be replaced as soon as it is noticed. If you see that water does not drain into old soil and kind of hangs out on top, the soil is waterlogged and the plant roots cannot access that soil.

Best of luck with this and all your plants!

OllieVet
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