I’ve noticed some orange-ish spots in the soil of my cactus plants which I am guessing is mould? I’m new to owning plants so I don’t really know what I’m supposed to do in terms of treating and preventing mould growth.

I don’t water them too often (about once or twice a month, depending on temperature and soil dampness) but I did recently repot them all and added some soil from an outdoor plant.

What should I do?

enter image description here enter image description here enter image description here

  • 2
    Does either of those containers you used have drainage holes in the bottom? And when you say you added soil from an outdoor plant, was it ordinary garden soil?
    – Bamboo
    Dec 4, 2021 at 12:52
  • No, neither of them have drainage holes. I know it’s not ideal but it’s all I have. And for the soil I’m not sure - it was from my household member’s strawberry patch.
    – ryuu
    Dec 5, 2021 at 12:56

1 Answer 1


You do need to repot them into something with drainage holes - it's important for any plant, but particularly cactus varieties. When you repot, remove as much soil as possible to try to get rid of the soil from outdoors; soil outdoors may contain pathogens which, whilst left out in the open, are not a problem, but may well be a problem when contained in a pot, and especially indoors.

I can't fully identify what's growing on the soil, can't see enough detail, but it could be early lichen growth or fungal growth which may have come from the garden soil, and will be encouraged by the fact there's no drainage in the containers.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.