Garlic Mustard (Alliaria petiolata) is a plant in the mustard family which has a strong smell of garlic when the leaves are bruised. It’s native to Europe, Asia and northern Africa, and was brought to North America as an herb to be used as medicine and in cooking, probably in the late 1800s. It’s now considered an invasive species and a noxious weed in the eastern U.S. and Canada.
Flowering Garlic Mustard
It’s a biennial, so it grows only leaves the first year. The second year it blooms, makes seeds, and dies.
First year seedlings, just coming up
Second year plants showing above dead leaves in the spring. The leaves are evergreen, so they can be found all winter.
Second year plants starting to send up their flowering stalks – around here that happens in early-mid April.
Early May – with flowers and a few seed pods
Each plant can produce hundreds of seeds so when it arrives, it dominates the woodland landscape.
A large patch of Garlic Mustard had taken over this part of our woods.
I found the first Garlic Mustard plants on our land in 2007, and now every year I find new infestations.
For the first few years, when I didn’t see much of it, I pulled the plants I found and removed them from the site. As the number of plants increased – exponentially – I gave up pulling, and started spraying because it was much faster. Every year there were more – I was losing the battle. I started giving up on the edges of our property – next to land belonging to neighbors who didn’t even try to control it. Every year I was defending a smaller and smaller area, but it took just as long because there were more plants.
In 2025 and 2026 I began reading about studies that had been done on the east coast – where garlic mustard has been a problem for many more years – showing that older infestations would eventually die back. I was skeptical at first, but the more I read, the more encouraged I became. The studies show that it’s important *not* to pull or spray it – to let it run its course. If the soil has GM growing in it, it accumulates pathogens that gradually discourage the GM. If the GM is removed, those pathogens don’t build up, and the GM thrives.
In 2026 I visited a small valley – one of the first places where I had given up on controlling GM. It’s near our neighbors’ property line, and it must have hosted many cows when our land was still a farm because the vegetation – even without the GM – was mostly bush honeysuckles with a ground layer of weedy natives.
Here’s GM Valley in 2016. The floor of the valley was dominated by thousands of GM plants. Mike helped me spray it that year.
I sprayed GM there for one more year, but gave up on it after about 2017 – it was just too much work.
I didn’t go back there for years – I was sure it would be a solid ground layer of GM and nothing else.
But here’s what it looked like in May of 2026. Still some GM, but not much. Most of the ground layer was those weedy natives that had been there in 2016.
And there were big areas where there was no GM at all.
So my new plan (as of May 2026) is to stop trying to control GM, and let the woods recover on its own. The research shows that the real problem – the one that drives GM infestations – is too many deer. Since that’s not something I can do anything about, I’ll just have to put up with that. It may mean I’ll always have some GM, but it looks like there will be less than if I try to control it, and without nearly so much work!
Information on treating vs. not treating GM:
Research paper – by Bernd Blossey, Victoria Nuzzo, Andrea Dávalos, Mark Mayer, Richard Dunbar, Douglas A Landis, Jeffrey A Evans, Bill Minter
Interview with Bernd Blossey
Webinar by Bernd Blossey
Biocontrol
Work on a biocontrol has been ongoing for many years. The weevil Ceutorhynchus scrobicollis was federally approved as a biocontrol for GM in 2025. Now it needs to be approved by individual states, and biocontrol companies need to propagate enough insects to be released. Releases will require both state and federal permits.
There are also a few other insects for which Garlic Mustard is a host plant – these are the ones I’ve found.
Garlic Mustard Aphids – a European aphid that feeds exclusively on Garlic Mustard.
Garlic Mustard plant with Garlic Mustard aphids
Garlic Mustard aphids
This aphid species was first spotted in North America in Ohio in 2021, and has since been found in several other states including Wisconsin. It eats the leaves and developing flower stalks. The plants I’ve seen with aphids on them didn’t flower – so I’m very hopeful that they’ll help control GM.
Snowy Geometer – found on and reared on Garlic Mustard. I don’t think this happens often – this is the only time I’ve seen it on GM.
Snowy Geometer adult – reared on GM, emerged on 7/7/2022
More information on Garlic Mustard:
Garlic Mustard – Wisconsin DNR
Garlic Mustard – Invasive Plants of the Eastern U.S.
Garlic Mustard – Wikipedia
PCA Alien Plant Working Group
More information about Garlic Mustard Aphids:
Prairie Haven
Bugguide
How to report aphid sightings