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Wait, is my houseplant growing mould? It probably is, but you can fix it

Dec 08, 2023Dec 08, 2023

By Zilla Gordon

There's good and bad news when it comes to mouldy houseplants.

Gardening experts say while the extra growth in our plants is very common, it's pretty easy to treat.

Harris Mashood, who owns a Melbourne-based plant shop, says overwatering can make for mouldy soil.

"The wet soil is actually a perfect breeding ground for dormant mould spores to thrive," he says.

"A lot of times, in our potting mixes, this dormant mould exists, which we obviously can't see, but that perfect situation of overwatering makes them thrive, and the mould starts popping up."

The grey-green growth might spark concerns from plant owners but, unlike household mould, Mr Mashood says it poses little risk to your health.

"When people first see this mould, they give us a call and they get really scared and ask if they should throw away the plant … but it's not harmful," he says.

The mould won't really harm your plant either, but Mr Mashood says it does drain a lot of nutrition from whatever you're attempting to grow.

"You don't want your actual plant to miss out on all the nutrients from the soil."

Mr Mashood says the growth normally forms on the top layer of the soil but, as the microorganisms in the soil react, you could even get some mushrooms.

"A lot of times its very cute to see these mushrooms growing, but other times, you'd rather just take them out because they take a lot of nutrition from your soil."

The appearance of toadstools is a good sign your potting mix is high quality and has all the nutrients to help your plants thrive.

Mr Mashood says the soil's mouldy top layer can just be scraped off.

"The other thing you can do is sprinkle cinnamon powder on top of the mould," he says.

"Cinnamon plays the role of a natural fungicide … and if you're growing something you want to eat, like tomatoes, I think some sort of natural remedy is always a good go-to."

If you don't want to use cinnamon, Mr Mashood says you can get some fungicide at nurseries or your local plant shop.

The one treatment he says to stay clear of, however, is vinegar.

"A lot of old-school people mention it, or maybe your grandmother will mention using vinegar," he says.

"Vinegar will not get rid of mould, and it could actually kill your plants as well."

If you feel your plants have little chance of resurrection, changing the soil may be a lifeline.

"You can create your own potting mix by adding a lot of perlite … or sand and once you have proper drainage, you shouldn't have the issue of mould growing," says Mr Mashood.

Your watering method can also help improve drainage by giving the "watering-up" method a go.

The method simply involves popping your plant into a saucer of water and absorbing the liquid from the roots up.

It can help reduce the amount of water on the topsoil, and the chance of mould growing.