Suddenly have an insect infestation after using potting soils? Tiny little gnats flying out of the soil in pots and your garden? Yeah, me too. I found out that they’re called fungus gnats, and they are certainly annoying!
I was so ecstatic to have put together my first raised bed for a vegetable garden. It’s nearly full with mushroom compost received from a neighbor, who got a huge haul at a local mushroom farm. The final touch was to add some garden soil to the top of the bed and plant some seeds.
Tiny Fungus Gnats in New Potting Soil
A special sale at a major home improvement store meant that organic Miracle-Gro soil was just $5 a bag – a pretty good deal. I got two and immediately added it to my bed.
(While this is my experience with this brand, I also tried EcoScraps potting soil and had the same fungus gnat problem. And plenty other people – see the many comments below – have also had issues with other brands, too.)
The next day, I went out to check on my raised bed and noticed the soil teeming with tiny little flies with white wings.
These insects were NOT in the compost before I added I the soil, yet appeared in droves within 24 hours of dumping the bag of soil into my raised bed.
I checked the mound of mushroom compost that I still had in another garden bed that was delivered the same day. Nope, the insects weren’t in there. I asked my neighbor if he had any problems with the tiny flies in his piles of compost. It was the same compost from the same delivery. That was a negative, too.
So I determined that the organic soil that I bought to complete my vegetable garden actually caused a HUGE problem that now I have to deal with.
Potting Soil Killing Plants
Maybe it was the compost, or just a coincidence, you might say?
Nope. I bought Miracle-Gro soil (the conventional kind) last year. I had three healthy houseplants that I had bought from the store and kept in pots for a few weeks that were fine. When I decided to finally repot them I bought one bag of soil. All three plants were planted in this same soil, and then placed indoors and outdoors in different locations.
ALL of the plants started developing problems and were infested with gnats. I lost $30 of plants, tons of time in taking care of them, and time spent to return the stuff to Home Depot where the cashier looked at me dubiously as to how my soil could have caused this.
Problems with Fungus Gnats and Potting Soil
Now, fast forward another year, and I’m researching gnat insect infestations online (I have SO much time in my life to do this, by the way) and finding out that this is a very common problem with Miracle-Gro, as evidenced in this stream of negative reviews on their website.
*Since the time I originally wrote this post, a string of positive reviews has flooded in. Check carefully and you’ll see that many of them are from sweepstakes entries (check in the description box). For non-sweepstakes reviews about gnat problems, filter the review search to one star reviews.
This is such an issue that the first comment for these gnat bait traps on Amazon speaks directly about using the baits to kill gnats on houseplants brought in due to Miracle Gro soil. Apparently these will work, but I haven’t tried them out.
Scotts response to past complaints is that it’s a natural product and not sterilized. True, I agree.
Their other solution in review comments is that there is a money back guarantee. How do I put soil back into a bag ripped in half in order to get the soil out? How do I return this nasty stuff to the store without getting it everywhere all over my car?!? Most importantly, what about MY time??? The time spent in researching this problem, in tending to plants at risk, to monitoring insect populations and in applying remedies to problems that Miracle-Gro acknowledges? Isn’t my time more valuable than the $5 that I spent on their bag of soil??
Check out my course on easy to grow, hard to kill houseplants to add to your home right now! These gorgeous plants will start detoxing your indoor air immediately:
Best Houseplants to Detox Your Home
How to Kill Fungus Gnats
Scotts response to all of the fungus gnat infestation comments and complaints on the review page has been that the gnats are not a problem to humans. And they cause little damage to plants.
Notice “little.” (Rolling my eyes…..)
The University of California Integrated Pest Management says differently. They state that a large infestation can kill seedlings or young plants.
The company’s response is also that adding 1/2 inch or more of sand to the top of your pots will help control the fungus gnats.
Which is good news for those of you who were wanting the look of houseplants planted at the beach or love the feel of the Sahara desert in your garden bed.
P.S. If you don’t mind the look of sand or rocks on your houseplants, here’s a recipe for how to get rid of fungus gnats using sand.
Also great for those of you who want to spend more money on unnecessary products when all you really wanted was a simple bag of potting soil and to be done.
But hey, now you get to go back to a garden center and buy sand and plant sprays and plant amendments. YAY!!!!!!
I had tried soaking my garden bed with insecticidal soap, which apparently doesn’t work on killing fungus gnats.
Adding sand to my garden beds was not an option for me. I was not going to buy a bag of sand, nor did I want to mess with this issue any more.
I basically just lost the entire garden bed and never went back to try again.
Related Posts:
- How to Get Rid of Gnats
- How to Keep Your Plants Alive While on Vacation
- Four Colorful Carefree Plants for Your Garden
Potting Plants in Compost
After this experience, I don’t buy potting soil at all anymore.
I use straight mushroom compost to pot my plants. I buy mine at Lowe’s, where the price is comparable to a bag of potting soil, but you can buy mushroom compost online here).
Everyone says never to plant your plants directly in compost. Maybe that’s for rich compost straight from the backyard. Or only cow compost. I don’t know. But what I do know is that I’ve never had problems planting any plant in mushroom compost or worm casings. It costs a little more, but I don’t have to buy soil amendments, fertilizers, insect sprays from bringing in gnats in potting soil, etc.
If you don’t want to avoid potting soil and use compost, then I suggest you don’t try to pinch pennies like I was. Go to your local garden center and get your potting soil from them.
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Where do you get your soil? Have you ever had an insect infestation with any other brand?
Judi says
I have been frustrated by tiny flying bugs… maybe gnats that come out of the soil after my house plants are repotted. I have switched brands but still have the issue. If I put out dishes of water that seems to catch them. I do not want to have dishes of water with dead bugs yet I love my plants. I have tried the sand on top and it seemed to work for a while but way too many plants to do that to all of them. It may have started in the MG cactus soil since succulents are a newer addition to my plants. I appreciate knowing I’m not alone, although a real solution would be best. I bought bags of a Burpee potting soil with coconut husks for my outside planters and then saw in the reviews that someone said it did not have bugs. I wonder if this soil would be best for inside. I got it with curbside pick up at Tracker Supply. Now it has not been in stock for months. Hopeful in CT! 😊
N says
Your first description of the gnats sounds a lot more like whitefly than fungus gnats! I’ve also found pests in miracle grow products and find that I need to put additives in the soil to address them (diatomaceous earth, mosquito bits, neem oil, insecticides, etc). I’m not sure using mushroom compost or worm castings is a viable alternative though, as these are extremely nutrient- and salt-rich substrates. According to one website, mushroom compost shouldn’t be more than a fourth of your planting medium: https://extension.oregonstate.edu/news/what-mushroom-compost. Instead, I’d recommend buying potting mixes from your local nursery, which generally come from smaller companies with better quality products!!
Natalie Guthrie says
Wow I’m sad and glad to know this problem doesn’t happen just at my stores. I just went to a big box store today because of the MG cactus palm and citrus soil. I had ants and what looked to be termites and after further research last night I discovered the fungus gnat issue in home depot’s reviews. I’m glad for their pictures because my bag had eggs like pictured. I brought the half of the bad I didn’t use back. The garden center manager gave me ortho 3-in-1 and told me to use it and to buy my soil elsewhere. I read about the product and its got great reviews. I didn’t try it yet because I didn’t plant my plants yet and need to confirm soil usage.
Mary thank you for your comment. I’m going to Google how to make soil since I’m reporting aloe and cactus!
Nicole Cordone says
THANK YOU SO VERY VERY VERY MUCH FOR THST AWESOME DETAILED POST AND DOUBLE THANK YOU FKR A SOLUTION TO THE PROBLEM!!!!!!! I SM WRITING THIS IN ALL CAPITAL LETTERS TO STRESS THE EMOTIONS I FEEL BEHIND IT! I HAD THE SAME EXACT PROBLEM AS YOU DID TWICE I HAD TO THROW AWAY OVER A HUNDRED DOLLARS OF PLANTS I COULD NOT SAVE NOT TO MENTION I WAS DEVASTED AND CREEPED OUT THE WHOLE TIME!!! I RESEARCHED THIS TOPIC ONLINE FOR A LONG TIME AND ALL PEOPLE WRITE IS THE TRICKS THEY USE TO KILL IT!! I WANTED A SOIL THAT SOMEONE WOULD RECOMMEND THAT HAD NO GNATS!! A FOUND A FEW BRANDS PEOPLE RECOMMENDED THEN I WOULD READ HOW THERE WERE GNATS FOUND IN THE SOILS THAT PEOPLE RECOMMENDING!!!! I WAS SO FUSTERATED THAT I GAVE UP AND ONLY BOUGHT PLANTS I COULD KERP IN WATER AND LITERALLY REFUSED TO EVER BUY SOIL AGAIN!!! SO I AM SO DELIGHTED TO READ ABOUT THE MUSHROOM COMPOST I AM GOING TO BUY IT RIGHT FROM YOUR SIGHT!!! I PRAY TO GOD THAT I DO NOT FIND GNATS, I WILL SPEND $100 A BAG IF I HAVE TO BECAUSE YOUR RIGHT THE MONEY DOES NOT COMPARE TO THE FRUSTRATING HELL YOU HAVE TO DEAL WITH THOSE AWFUL THINGS!!! THANK YOU AGAIN FROM THE BOTTOM OF MY HEART, NICOLE
Marcy Hendrix says
I wondered why all of my house plants developed fungal gnats! I have now come to the realization that it is the potting soil as I repotted all of my plants with miracle gro. I just read reviews about their Organic Raised Bed Soil. Several people found the soil full of plastic pieces, ceramic pieces, trash and bugs including fungal gnats, cockroaches and turmites!!!! How can a company continue to sell their product, knowing that their soil is contaminated? I am going to my local garden store and buying their soil!
Paul says
It is good that you mention this problem on your blog because it is really common. I had problem with them once but it was definitely my fault. They appeared in the pot of my pelargonium. It wasn’t easy to get rid of them but I bought a special preparation that somebody in garden shop recommended me a preparation. It was a flying insect killer and it really worked so good!
Michelle says
Thank you for the post! Was repotting plants and suddenly saw a gnat crawling on the table! I was so creeped out by the thought that this large bag of miracle grow nature cure was crawling with gnats. I ran the bag out side in 20 degree weather! Contacted MG and they said it’s not their fault… it’s how soil was stored… it’s a natural product .., blah ..,blah. Never thought of mushroom compost but after your post will give that a try. Thanks!
Kimberly Button says
I think any bagged item could potentially have problems. That’s what makes it challenging. Always open up the bags outside first and wait a while to see if stuff starts flying out of them, LOL!
Mary says
I’ve also been bothered by fungus gnats in bagged soil. They are especially dangerous for seedlings and small plants and can easily kill them. I grow in a greenhouse and lately I bake well hydrated soil in the oven for a couple of hours. It takes care of the gnats but it is a lot of trouble. I grow succulents and soil is just one component of my mix so a little goes a long way.
Kimberly Button says
Thanks for sharing, Mary. That does seem like a hassle, but if you use a little bit it seems like a step worth taking.