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The Best Way to Get Rid of Garlic Mustard, an Invasive Weed

Caren White is a Master Gardener and instructor at Home Gardeners School. She has been associated with Rutgers Gardens for over a decade.

A stand of garlic mustard that has choked out other plants on the forest floor.

A stand of garlic mustard that has choked out other plants on the forest floor.

Ugh, it’s garlic mustard season. The roadsides, the woodland edges, seemingly everywhere I look, garlic mustard is blooming. What is it? Where did it come from? Most importantly, how do you get rid of it?

What is Garlic Mustard?

Garlic mustard (Alliaria petiolata) is also known as Poor Man’s Mustard, Hedge Garlic, Garlic Root and Jack-by-the-Hedge. It is an invasive plant found throughout the Northeastern and Midwestern US as well as Southeastern Canada. It is called garlic mustard because the leaves have a garlic smell when they are crushed.

It is a biennial plant meaning it completes its life cycle in two years. The first year, it grows a rosette of leaves. The rosette appears in mid-summer when the seeds germinate. In areas with warm winters, the rosettes remain green throughout the winter, photosynthesizing the sunlight while other plants are either dormant or have no foliage. This gives it a head start in the spring of the second year of growth.

The second year, the rosettes grow into a plant that can be up to 3 feet tall. In late spring, May through June, the plants bloom. The flowers are white with 4 petals arranged in the shape of a cross. The flowers develop seed pods. Each pod contains about 16 seeds. Each garlic mustard plant produces, on average, 600 seeds. When the pods are ripe, they forcibly eject the seeds several feet away from the originating plant. The seeds can stay viable in the soil for up to five years.

The first year, the plants form a rosette of leaves.  An easy way to tell if a rosette is garlic mustard is to smell the leaves.  They will smell like garlic.

The first year, the plants form a rosette of leaves. An easy way to tell if a rosette is garlic mustard is to smell the leaves. They will smell like garlic.

Where Did Garlic Mustard Come From?

Garlic mustard is native to Europe, Western Asia and Northern Africa where it is found in hedgerows and along the roadsides and forest edges. It has long been used as food and medicinally as a diuretic. In it native areas, it is kept in check by 76 different kinds of insects including butterflies and moths which lay their eggs on it. The resulting caterpillars feast on the leaves.

How Did Garlic Mustard Get to the US?

Some say that European colonists brought garlic mustard to the New World to use as they did in their old homes, flavoring food and as a medicinal. Others say that garlic mustard was brought to the US accidentally either in the soil of other plants that were brought here or as seeds stuck to the soles of boots. However it got here, the first recorded appearance was in 1868 on Long Island. Since that time it has spread throughout 30 US states and 3 Canadian provinces.

The second year, garlic mustard grows into a plant that can be three feet tall.

The second year, garlic mustard grows into a plant that can be three feet tall.

Why is Garlic Mustard Considered an Invasive Plant?

Garlic mustard is considered an invasive plant for three reasons. The most important one is that it has no natural enemies in North America that could keep it under control. The second reason is that due to its large seed production, it spreads quickly and crowds out other native plants. This is especially critical in forests where it replaces all native plants found on the forest floor.

The third reason it is considered an invasive plant is its long tap root. Normally plants with long tap roots only have one plant growing from the root. The tap root of garlic mustard has the ability to grow additional plants from buds that form along the root. Additionally, the root is allopathic meaning it excretes chemicals that prevent other plants from growing near it. This includes tree seedlings, another reason why a garlic mustard infestation is so disastrous for forests. The chemicals exuded by the tap root are also harmful to fungi in the soil that is needed by the roots of other plants.

The flowers have four petals.  They form seed pods (the long green rods in the photo) which contain 16 seeds each.

The flowers have four petals. They form seed pods (the long green rods in the photo) which contain 16 seeds each.

The Best Way to Get Rid of Garlic Mustard

The most popular way to rid the landscape of garlic mustard is the use of herbicides such as Roundup. The problem with any herbicide is that it doesn’t distinguish between the good guys and the bad guys. It will kill all plants. As an organic gardener, I stay away from herbicides.

Garlic mustard is edible, tasting like garlic, so another way to get rid of it is by eating it. Unless you are feeding a lot of people though, this is not an efficient way to get rid of it.

The best way to get rid of garlic mustard is manually, i.e. pulling it up and discarding it. You should strive to pull up the plants before they set seed because the action of yanking the plant from the ground will spread the seed. I recommend waiting until after it rains to start removing it. The wet soil is looser making it easier to pull up the plants. You will more likely get all or most of the long tap root when you pull the plant out of the wet ground. Like dandelions, if you don’t get that tap root, the plant will grow back.

After you have pulled the plants, resist the temptation to throw them in your composter. Either burn them if burning is allowed in your area or bag them up and throw them out with your garbage. They will be deeply buried in the landfill.

Manually removing garlic mustard is not only labor intensive but it is also a long term project. The seeds remain viable in the soil for up to five years, so the plants will continue to reappear in subsequent years. That is why it is so important to remove them before they go to seed.

At first, it may seem like a losing battle, but if you watch carefully, you will see that native plants and even tree seedlings steadily re-populate the areas where you have removed the garlic mustard. They are proof that you are helping the forests and other areas return to health.

Questions & Answers

Question: When I am walking in the woods and see a large patch of garlic mustard, what is the best way to dispose of the pulled plant? Drop it on the ground where it is picked or walk to a path and drop the pulled plant?

Answer: You should do neither. Like all trash, you should carry it out of the woods and dispose of it in a trash bin or if there is nowhere to throw it out at the park, take it home and throw it out with your own trash. If you leave it in the woods, it can spread seed or take root again. Your aim in uprooting the plant is to remove it completely from the environment. That can only be done if you deposit any garlic mustard plants that you pull up in the trash.

Question: Where are the garlic mustard seeds?

Answer: After the flowers die, the seeds are produced in their place. So wherever you see flowers on the plant, that is where the seeds will be.

© 2019 Caren White

Comments

Caren White (author) on May 29, 2020:

Thank you for your information. I live in NJ where the laws are different. I don't recommend composting garlic mustard on your property because it is likely to either take root in your composter or if there are seeds present, they will then be spread in your garden when you use your compost.

anon on May 28, 2020:

Please check your local laws. In Minnesota, it's illegal to transport noxious weeds like garlic mustard unless you're taking them to a yard waste site that specializes in this kind of weed. Also illegal to throw them in the trash. If you can't burn them, you're supposed to leave them on your property in a pile to decompose.

Caren White (author) on May 27, 2020:

That's correct. As long as the seeds have not yet formed, getting rid of the plant will prevent seeds from developing. Just remember that any seeds already in the soil can still germinate so it takes a few years to get rid of garlic mustard completely.

sharoncathcart@hotmail.com on May 27, 2020:

So, if the flower breaks up while I pull it, the seeds are not being dispersed at the same time, but have yet to be created in the plant. So, disposing of the plant even if the flower petals fall off eliminates the seeds?

Caren White (author) on May 04, 2020:

It's not a good idea to compost garlic mustard plants because they are alleopathic. They secrete chemicals that prevent other plants from growing near them. This means that the composted the harmful chemicals from the composted garlic mustard will kill plants in your garden when you add compost to it. It is best to toss garlic mustard plants in the garbage.

TD on May 03, 2020:

When the garlic mustard is flowering in spring before seeds develop can you compost it ?

Caren White (author) on June 06, 2019:

That sounds like a really good idea! If garlic mustard is a problem in your area, perhaps you can suggest it to your local restaurants.

Viet Doan from Big Island, Hawaii on May 31, 2019:

Fascinating that it is edible! I wonder if the local restaurants would use large quantity of them to make salads, soups or pesto sauces. It could become a trendy way to get rid of this unwanted, prolific weed! I greatly enjoyed the article, thanks for sharing Karen.