A Field of Garlic Mustard


A foggy look south from atop the West Bluff. Photo by Sue Johansen, Park Naturalist.

 I love foggy days at the lake. We were up on the west bluff last weekend, before the 3 inches of snow came, to enjoy the signs of spring that were starting to crop up. One sign was the ice off the lake (a week earlier than last year). It seemed to happen over night - Friday night the ice was there and by Saturday morning it was gone! We saw other signs of spring up on the bluff. We saw hepatica starting to bloom. Dutchman’s breeches had green leaves and a few had flower stalks. There was green starting to come in here and there and a lot of the green was coming from garlic mustard.


Hepatica just starting to bloom.

Garlic mustard is the bane of woodland areas. It can spread rapidly and can dominate can take over an area, displacing most native vegetation, within ten years. In that short time, all of the woodland flowers we enjoy seeing in the spring are gone; lost in a sea of garlic mustard.

Garlic mustard has two growth phases.  The first-year plants are small, rising only 2 to 4 inches above the ground. The basal leaves have 3 to 4 round, scallop-edged leaves. These basal leaves appear in late spring and early summer and remain green throughout the winter. During its first year, the plant will not flower.


First-year garlic mustard. Notice the scalloped edges on the leaves. Photo by Sue Johansen, Park Naturalist.

The second-year plants generally produce 1 to 2 flowering stems that can grow 12 to 28 inches in height. Each stalk will bear numerous white flowers. In Wisconsin, you will start to see the flowers early in May; but this is all dependent on the type of spring we have. The flowers, once pollinated, will become slender fruit capsules that can be 1 to 2 ½ inches in length. Each pod contains a single row of black seeds and each plant can produce hundreds of seeds.


Garlic mustard – 2nd year growth with it’s white flowers. Photo from the National Park Service

What really helps this plant spread is the viability of the seeds. Garlic mustard seeds can lie dormant for about a year before germinating and can remain viable in the soil for up to five to seven years. The seeds also have several ways they can travel to new areas. They can be carried on the fur of animals, by flowing water, or by human activity. Unlike most weedy plants that only grow in disturbed areas, garlic mustard readily spreads into high-quality forests. It starts its invasion from the wood’s edge by spreading along stream banks, walkways, and trails then working its way to the forest interior. It can grow in a variety of soils.


A small woodland taken over by garlic mustard.

So how does one control such an aggressive weed? There are several methods that one can try. Hand-pulling is the most effective for small population. Pulling does have its disadvantages. It causes soil to be disturbed bringing up other garlic mustard seeds that is dormant in the soil. Pulling can also cause damage to the desirable plants. For larger infestations, burning or use of chemicals can help to control the population. Fire works best for first-year plants if the fire is hot enough to burn the leaf litter. People have had success using propane torches on the first-year plants. This does not damage the leaf litter and can be used any time during the year without worry about damaging other vegetation in the area. Herbicides, like Glyphosate or Round-Up©, are often used to control large populations of garlic mustard, especially if there lots of second-year growth. Since glyphosate is a nonselective herbicide, it will kill native plants as well. Spraying with this herbicide is best done in late fall or early spring during the dormant season for native plants.

If you’d like to help control the invasion of garlic mustard here at the park, we are always looking for volunteers at Devil’s Lake to help pull garlic. Join us for one of our “Weed Buster” evenings (see below for dates and times) or feel free to come out an pull it on your own.

If you pull plants on your own, please  . . .

  • If the plant has started to flower or has any seeds on them, please DON’T leave them on the trails. The seeds can still mature and spread down the trail during rain storms, making the problem worse.
  • You can remove the flower and seed-heads and put them in a plastic bag to be thrown in the trash. The rest of the plant can be left to decompose.

If you have any questions, contact the Nature Center at (608) 356-8301 ext. 140.

Weed Busters!

Tuesday Evenings Starting at 6 pm

Garlic mustard has becoming more and a more of a problem in the park in the recent years. We are looking for volunteers to help us remove it throughout the park.

If you are interested in helping, join us on the following evenings:

  • Tuesday, April 22
  • Tuesday, April 29
  • Tuesday, May 6
  • Tuesday, May 13
  • Tuesday, May 20
  • Tuesday, May 27

We’ll announce each week where we’ll be working.

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