Garlic Mustard, A Threat to the Wooded Areas of Wisconsin

This past week I was out planting some shrubs in the interactive walking trail, a wooded walking path area in Montello.  I noticed that a plant that I don’t like to see in a wooded area, garlic mustard, has already emerged for the season while some of our native shrubs and plants are still “sleeping”.  What is garlic mustard, and why don’t we want it in our wooded areas?

Garlic mustard seedling on brown soil background.

Garlic mustard seedling that has just emerged recently. Photo by Lyssa Seefeldt.

Clump of garlic mustard that is flowering.

Garlic mustard flowering in summer. Photo by Lyssa Seefeldt.

Profusion of garlic mustard in various stages from seedlings through flowering plants.

Garlic mustard in various stages from seedlings through the flowering stage. As you can see by the amount of garlic mustard plants in the photo, garlic mustard easily outcompetes other plants in wooded areas. Photo by Lyssa Seefeldt.

Garlic mustard (Alliaria petiolata) is an introduced species in North America that was originally brought here by settlers from Europe.  Part of the reason that the settlers brought the plant here was for use in cooking due to the garlic-like scent/flavor that the name implies.  One of the issues with garlic mustard is that none of the insects and diseases that would naturally control the population of plants are present in North America.  Combine that with this plant having an earlier growth in the spring and garlic mustard can often outcompete native plants and tree seedlings for space in the understory.

Garlic mustard is a biennial plant.  It starts growing in the first year as a rosette, usually emerging sometime in April.  Leaves are round with a scalloped edge.  The plant is usually a chartreuse green.  The plant has a characteristic garlic odor when crushed.  In the second year, a flowering stem will emerge, and plants may reach three to four feet in height.  At this point the leaves will be more triangular in shape.  Flowers are white and rather tiny with four petals.  After flowering is complete, long, slender seed capsules will appear.  Each plant can produce up to 500 seeds.  Mature seeds are tiny and black.

Control of garlic mustard can be a challenge due to the productivity of each plant, the early emergence in spring, and the fact that seeds have been known to survive in the soil for up to seven years.  The Wisconsin DNR recommends using control strategies for eight or more years in a row to control infested areas.  This will eventually deplete the seed bank in the soil.  It is easiest to control an infested area when there are only a few plants to deal with.  Once the plant flowers and produces seed, it takes much more effort to eliminate.

For areas that only have a few plants, especially ones that are first-year plants, hand pulling can be an effective method of control.  For large areas of infestation, additional measures may need to be taken.  Timing of control measures are going to be important to prevent additional seed development.  For recommend control methods of larger areas, please view the WI DNR factsheet on garlic mustard at

Another thing to remember when working on control of garlic mustard is to control inadvertent spread of the seed.  This includes cleaning shoes and clothing, as well as equipment after working in an infested area.  Routinely check your area for plants throughout the year.  When working in an infested zone, identify the whole area of infestation, including any area that has garlic mustard plants.  You want to work from the least infested to the most infested area to prevent seed travelling further outward from the “hot spot”.  Remove plants bearing seed first, then go back to the plants that don’t have seed and remove them.


Note: This article originally was published in the Marquette County Tribune, Waushara Argus, and/or the Berlin Journal.  This article was written by Lyssa Seefeldt, UW-Extension Agriculture Agent for Marquette County unless otherwise noted.