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Gnats are one of those things that plagued the early days of my house plant
obsession hobby but they’re not a big deal now.
I think it’s because I learnt how to get rid of them, but there’s also the chance that I just got used to them.
I know they’re annoying but they’re not *that* difficult to get rid of.
It can seem like an easy solution, but if you don’t know how to get rid of them (or stop them from showing up in the first place) they’ll just come back.
Why does my Monstera have fungus gnats?
Fungus gnats eat fungus. Fungus grows on the top of house plant substrate.
Your Monstera has fungus gnats because it’s not only providing them with, food but also a lovely habitat for them to thrive in.
So, your Monstera doesn’t just have fungus gnats.
It’s freaking raising them. Nurturing them.
Your Monstera doesn’t care that having flies drowning in your Friday night prosecco really ruins the vibe.
Fungus gnats often turn up in the soil.
Some store-bought potting mixes are well-known for bringing fungus gnats with them *cough* Miracle-Gro *cough* but it’s kind of inevitable. Just…avoid that brand if you really hate gnats. They can be gotten rid of though!
Are gnats bad for Monstera?
No, not really.
There are rumours that the larvae can eat the roots, but that’s highly unlikely.
The larvae would only eat Monstera roots if there wasn't any fungus for them to eat*, and if there wasn't any fungus to eat, they wouldn't have chosen your plant to live in.
Also, Monstera are known for their penchant for growing a root system far bigger than what’s strictly required.
A healthy Monstera root system has nothing to fear from fungus gnat larvae.
The issue is that having an excessive amount of fungus gnats can be a sign that you’re overwatering your Monstera.
Fungus gnats only live in the top layer of the soil, and the top layer shouldn't stay wet enough to provide a habitat for a lot of gnats.
The odd one, though annoying, is pretty much inevitable, but a lot is a sign that there’s too much water in your soil. If you’re overwatering, that can lead to root rot.
As the roots rot, the decaying matter provides nourishment for the fungus gnats so I guess *technically* they’re eating the roots, but only after they’ve ceased being of any use to the plant.
*It’s not fungus as in full-on mushrooms. It’s really just decaying matter, which is a byproduct of having a really good, healthy, biodynamic potting mix.
Yellow sticky traps
Yellow sticky traps are a low-cost, easy way to get rid of fungus gnats.
I don't like them because they seem cruel. I don't have the time to be weighing up the ethics of killing gnats so I find it easier to not use them. If it doesn't bother you, go ahead.
You can also get blue ones – they’re designed to attract thrips. I also haven’t tried them, but let me know if you have and whether or not they work.
Yellow sticky traps are a bit like neem oil – for every person saying that they’re extremely effective there are ten more saying they’re useless.
Try them out if you want to – the thing about reviews is that if something works as it says it will, people don’t tend to leave reviews. If it doesn’t work, they’ll leave a scathing review.
Neem oil is more of a preventative thing. I add a drop to a spray bottle, fill it with water and use it to clean my plants.
Over time the oil affects the gnats’ ability to reproduce and eat. Obvs this is NOT a sustainable way to live and they die off after a while.
I don't know why this doesn't bother me but the sticky traps do. Probably because I can see little fly corpses on the yellow paper. Some vegan I am.
Bottom watering is a great way to stop fungus gnats. Sit your plants in water, and let the water wick up through the soil, but remove the plant from the water before the top gets wet. That way, you’re not providing a habitat for the fungus gnats.
I go through phases of loving bottom watering and others of being too lazy.
It really suits some people but not others.
If you have the space to keep a bottom watering pan out all the time, it can be a super simple way of keeping your plants watered, because it’s always ready to go.
If you don’t have space, you can end up knocking bowls of water onto the floor all the time (source – my life).
Diatomaceous earth is a great way to get rid of fungus gnats. It’s best paired with bottom watering because the powder needs to dry for it to work.
DE is basically finely milled glass that you layer on top of your soil. When it’s dry, it basically kills the gnats as they come up from the soil to feed.
It’s very effective, pretty cheap and easy to get hold of.
The only issue is that you NEED to wear a mask when you use it.
Your lungs with not thank you if you fill them with what is effectively tiny shards of glass.
Another benefit of diatomaceous earth is it’s a source of silica for your plants, which can help them to grow physically stronger, which can help them prevent damage from stress and pests like thrips.
No DIY fertilisers
You remember that I said that fungus gnats love a bit of decaying matter? That ESPECIALLY includes things like banana shells and eggshells – you know, all those things Pinterest says your plants will love.
Your plants may love them but so will fungus gnats.
Not only that but they'll bring their friend the fruit fly to the party, which are very similar in terms of physical appearance and propensity to fly around your face and into your wine.
Any stinky fertiliser (bar, bizarrely, seaweed fertiliser) can attract gnats. If you’re only interested in natural fertilisers and don’t want to use any chemical ones I strongly suggest you stick to worm castings or seaweed fertilisers.
Employ a cleanup crew
This really freaks out a lot of people but I quite like a more natural approach to growing house plants.
I naturally have a lot of things like springtails and isopods in my soil, because we add them to the terrarium to keep everything in balance and…they escape.
There are very few creepy crawlies living in the soil that will damage your plants – at least indoors. You might encounter things like slugs and snails, but I’m gonna assume you know about them.
In general, house plant pests like thrips and spider mites live on the plant. Things living in the soil tend to be feeding on the soil and will help keep it healthy.
If you do want to buy a clean-up crew, I’d start with Springtails. They’re tiny, innocuous, and do a great job.
Isopods are extremely fun to watch (don't knock it till you try it - they're way more soothing to watch than fish, and I say that as someone with a lot of fish) but they breed prolifically, and in my experience get bigger as they reproduce (unless we're just over here growing massive isopods accidentally). They also crawl all over the house, whereas springtails stay put.
These bugs won’t predate on fungus gnats, but they will eat their food and discourage them from setting up shop.
Don’t buy, e.g. frogs or geckos to eat the gnats because they’ll go through them quickly and you’ll end up having to buy them flies to eat, which is the opposite of what we’re trying to do here.
Fungus gnats are annoying, but they won’t harm your Monstera. They tend to turn up when the top of the soil is too moist, so make sure you’re not overwatering.
Oh, a lot of people swear by mosquito bits, which are granules you can add to your potting mix.
I don’t think they’re available over here, but you can try it if you can get it.
I personally don’t like using anything systematic like that because I like my soil to be full of microbes and bugs that help keep the soil healthy.
However, I'm also the kind of person that thinks nothing of picking up a slug with my bare hands and putting it outside. I move spiders onto my plants so they'll eat gnats. I
kidnapcollect ladybirds to eat aphids.
If you have a bug phobia, by all means, use a systematic pesticide.
If sharks were a problem in my home I’m pretty sure I’d employ any means in my arsenal to get rid of them, but luckily for me my phobia is content to live in the sea (except fucking bull sharks) and I’m content to stay out of it.
Good luck with getting rid of the fungus gnats on your Monstera!