MADISON – Many landowners, gardeners, hikers and hunters are all too familiar with garlic mustard, this invasive species can spread quickly and Wisconsin’s citizens are reminded to pursue aggressive management actions when possible.
“Garlic mustard is easily identifiable in the spring – it lives through the winter as low green rosettes and as soon as warm weather hits, it sends up a flowering stalk, usually about 2 1/2 feet tall,” said Kelly Kearns, Wisconsin Department of Natural Resources plant conservationist. “It branches out, bearing many small four-petaled white flowers. Identification can be verified by crushing the leaves that smell of garlic.”
Garlic mustard can significantly alter the composition of entire forests. When this species enters a woodland, it quickly spreads and can dominate the forest floor. Garlic mustard often displaces native wildflowers and ferns and many tree seedlings, and the wildlife that depend on them. It can even have an impact on mature trees as chemicals produced by the garlic mustard kill the beneficial mycorrhizal fungi that tree roots need to absorb nutrients.
“Garlic mustard must be dealt with in an aggressive fashion, and control efforts should be conducted in spring before the plants flower. This can be done by hand-pulling, spraying, or burning,” Kearns said.
Hand pulling is the easiest and most effective way to control new or small populations, and careful application of herbicide can be used to control larger populations. To more quickly get control of a population, it is best to also spray the rosettes in the fall. Running a flame over young seedlings is very effective, but should be done on a damp day, when the chance of fire spreading can be minimized.
Once they begin to flower, pulled garlic mustard plants left on the ground can continue to develop seeds. To avoid this, plants should be burned, buried or bagged. While Wisconsin has a law that does not allow yard waste to be landfilled, there is an exemption for garlic mustard and other legally prohibited and restricted invasive plants.
Several weeks after pulling or spraying, return to the site and remove any flowering plants that have since emerged. Garlic mustard seeds can remain viable in the soil for seven to 10 years. Forested sites without garlic mustard should be inspected for new infestations several times a year.
Informational brochures may be available at your local University of Wisconsin Extension office or DNR Service Center. For more information on garlic mustard and other invasive plants, visit dnr.wi.gov and search keyword “invasives.” More garlic mustard photos are available on the DNR website.