Question
Hi,   I have a number of different coloured Zygo Cactus.
A couple of them have the leaves turning a dark red and they get wrinkled and don't look too healthy.   After several weeks they tend to rot off at the soil level in the pot.

There are more and more of my plants suffering in this manner.
I have the cactus in hanging baskets in a covered pagola.   The roofing material is a plastic type roofing material which filters the light to about 60%.

I water the cactus by mist spraying from above.   The water comes from a rainwater tank.

Please advise

Answer
Hi Greg,

You have an unusual set-up for your Zygocacti and a number of things going on, so it is hard to know just what the cause of the leaf purpling is.

The wrinkled appearance on the leaves suggest that the leaves are not getting adequate water. That could because the soil is getting too dry or because it has stayed too wet and the roots are now rotting and no longer able to absorb water. Watering via a mist system is very tricky and hard to control, but I suspect at least part of the problem is related to that. Pay special attention to the depth that the mist penetrates.

Light is another issue that may be related. Depending on the composition of the plastic roofing, your plants may be getting too much or too little light and certain portions of the light spectrum important to plant growth may be filtered out.

Finally, soil and water acidity (pH) may be a problem. Rainwater is usually fine in this regard, but the tank may be having an effect on the water pH and mineral content.

Sorry, I can't be more definitive here, but I think I have at least given you some areas to explore.

Please let me know if any of this is unclear or if you have any additional questions. If you would like to e-mail me some photos, I may be able to provide some additional insights.

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Regards,
Will Creed, Interior Landscaper
Horticultural Help, NYC

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