Invasive Hitchhiker: Garlic Mustard

Contact(s): Donna Peppin

Michigan's Upper Peninsula has many relatively well-known invasive plant species including spotted knapweed, St. John's wort, glossy buckthorn, and purple loosestrife. Garlic mustard is the latest invasive plant species non-native to the local environment to join the list of unwanted plants that cause significant damage to food chains, natural ecosystems, and habitat for native species. 


Garlic mustard is on the rise and not as well established in the U.P. as other non-native invasive plant species. This factor along with its being "easy-to-pull" means that we have the opportunity for early detection of and rapid response to new infestations in order to control and minimize population spread.


Where did this invasive plant originate? Garlic mustard is a biennial, rapidly spreading herb native to Europe and parts of Asia. People brought garlic mustard to North America for food and medicinal purposes. It thrives in deciduous forests, but is also found along roadsides, trails, upland flood plain forests, and yards.


What does the plant look like? In the plant's first year, it grows as a rosette with one to several scallop-edged and dark green leaves. In the second year, stalks emerge from the basal rosette typically in mid-May to early June.

Garlic Mustard

Garlic Mustard


During flowering phase, garlic mustard produces white flower clusters at the top of the stalks. These flowers can produce a multitude of seeds that may remain viable for seven years or longer. Garlic mustard emits a strong garlic odor when the leaves or stem is crushed, which may be helpful in identifying the plant.


Several adaptive traits give garlic mustard a "competitive edge" against our local native ecosystems. Garlic mustard leaves emerge earlier than many native spring wildflowers and tree seedlings. Garlic mustard also releases biochemicals into the soil that inhibit growth of nearby plants. Each plant can produce thousands of seeds, which may stay viable in the soil for ten years. The chemical properties of garlic mustard's leaves can also kill some butterfly larvae when they feed on the plant's foliage. Because of all these competitive strategies, garlic mustard spreads quickly, often replacing native spring wildflowers and many hardwood seedlings with a monoculture of garlic mustard.


Recreational use has been one of the leading factors in the spread of garlic mustard. The plants' seeds and other plant parts cling to clothes, vehicles equipment, or animal companions, resulting in inadvertent transfer to new sites.


Equestrian use is just one of the many facilitators of garlic mustard spread along trails and trailheads. If you are a frequent horseback rider, be sure to purchase weed-free feed. Otherwise, horses pass the seeds through their digestive systems and deposit them at new locations where the invasive seedlings will emerge. Also, try to prevent your horse from eating garlic mustard in fields or hay, as this also spread the seeds to new sites.


There are other ways to help stop the spread of invasive species to new areas when recreating. First, be aware of the potential invasive species in your area, and learn how to identify them. If you are in an area where garlic mustard is present, be sure to brush off your shoes, bike tires, camping equipment, and/or other recreational equipment before leaving the site. Many campgrounds and other parks now have boot brush stations to prevent the spread of seeds on shoes, but make sure you also clean your boots after each excursion.


Years of repeated hand pulling and monitoring in garlic mustard infestations has shown some success with smaller plants and less reproduction noticed each year. Before pulling garlic mustard, be sure that you have properly identified the species "Don't pull if you don't know."


Also, have a garbage bag to dispose of the plant materials. Leaving the plant on the ground may result in further spread, especially if it is in the flowering stage. Alternatively, you can take it home and cook it up since garlic mustard in both edible and nutritious!


Be sure to report infestations to your local Conservation District or Forest Service Office. You can also report invasive plant populations on the Midwest Invasive Species Information Network (MISIN) phone app managed by Michigan State University and utilized by area conservation organizations.


For more information about the Forest Service's invasive species management efforts on Hiawatha National Forest, please contact the Donna Peppin, West Zone Ecologist, at 906-387-2512.