- Garlic mustard is an herbaceous plant found in the understory of high-quality woodlands, upland and floodplain forests and disturbed areas.
- It inhibits beneficial fungi associated with native plants, causing a decline in herbaceous vegetation within five to seven years.
Garlic mustard should be reported. Learn how to report invasive species in Minnesota.
Garlic mustard (Alliaria petiolata) is an invasive biennial herbaceous plant. Garlic mustard is a restricted noxious weed, meaning it cannot be transported, introduced, or sold in Minnesota.
One challenging aspect of garlic mustard, aside from how easily it spreads, is its effects on other plants. Studies suggest the plant is allelopathic, which means it releases chemicals that can hurt the growth of its neighbors.
Over time, a large patch of garlic mustard can severely damage native plant populations that would otherwise thrive in the area. It has been shown to cause harm to native plants including trilliums, trout lily, red maple and sugar maple.
Garlic mustard also thrives with disturbance, making places that are already impacted by earthworm damage and deer browse especially susceptible to invasion and difficult to control.
How to identify garlic mustard
- It forms a rosette in the first year, one to six inches tall, and grows to one to four feet high in its second and flowering year.
- Often the only plant of this height blooming white in wooded environments in May.
- Weak single stems.
- Dark green leaves are round with a scalloped edge.
- Second year plants have alternate leaves. Leaves and stems smell like onion or garlic when crushed.
- Leaves remain green throughout the winter.
- Numerous small, white flowers with four separate petals are present on second year plants.
- Slender capsules, one to two and one half inches long, containing a single row of oblong black seeds.
- Seeds mature in July or August and are viable in the soil for five years.
- Spread along wildlife trails.
- White, slender taproot, S-shaped at the top.
- If pulling plant, need to remove the root.
Because garlic mustard is a biennial plant, the first year of its life is spent as a rosette of leaves low on the forest floor. It is often confused with either wild ginger (Asarum spp), creeping Charlie (Glechoma hederacea), or violets (Viola spp) due to its kidney bean-shaped leaves. Luckily, garlic mustard also tends to be true to its name, as crushing the leaves can give off a mustardy, garlic odor.
Its first-year leaf edges are scalloped with blunt, shallow teeth. Second-year leaves look more triangular further up the stem, but they will still have scalloped edges.
Unlike creeping Charlie and wild ginger, garlic mustard does not spread vegetatively. If you pull garlic mustard plants you will not find runners or rhizomes, but a single crown with an S-shaped root attached.
Garlic mustard populations can be patchy and very localized. It is important to report any plants you find in order to help control spread. If you find garlic mustard, report it using either the Great Lakes Early Detection Network smartphone app (available free for iOS and Android) or the EDDMapS Midwest website.
Preventing the introduction and spread of garlic mustard to new locations is the most effective form of management. Seed is spread primarily by gravity, but it can be carried to new locations by people and wildlife, such as in seed mixes or soil attached to boots. Thoroughly cleaning shoes, clothing and equipment after hiking is good practice, as is buying seed from reputable sources.
For more information about prevention visit PlayCleanGo. Most importantly, make sure you spread the word about prevention to others!
If the area is small, hand removal of the plant and most of its root system is an option.
For larger sites, herbicide applications are generally the favored technique. If you decide to go this route, a labeled herbicide that contains the active ingredient triclopyr (Garlon) or glyphosate can be effective. Be aware that glyphosate products are non-selective, and will harm most actively growing plants if sprayed. Triclopyr normally does not hurt grasses and sedges, as it is active only on broadleaved plants.
Always read and follow the label before applying any herbicide.
Herbicides are best applied in April on second-year plants, and October or November on first-year plants, when many native plants are dormant.
Properly dispose of plant parts. Bag and remove seed pods, but consider composting non-fruiting material (leaves, stems) on-site to avoid large-scale nutrient export and keep soil healthy. Flowering plants with no silique production prior to pulling can be fully composted on-site with no risk of seed production. See the Minnesota Department of Agriculture’s Guide to Removal and Disposal of Noxious Weeds in Minnesota for guidance on what to do with the removed materials.
The UMN Extension Prioritizing Invasive Plant Control worksheet can help you identify high-priority management areas, and the Invasive Plant Management Decision Analysis Tool can help you determine the long-term feasibility of management on a site. Land managers may also find the Garlic Mustard Management Decision Tree from the Midwest Invasive Plant Network a good resource.
The best time for physical removal is early spring when plants are in bud or full flower, and before seed pods (siliques) begin to form. However, it is easiest to scout for garlic mustard rosettes in the late fall, as it is one of the last green plants in the woods. Take that opportunity to identify and map priority management populations for spring removal.
Monitoring for and placing the highest management priority on satellite populations or newly colonized areas helps prevent garlic mustard populations from expanding to sizes that are challenging to manage. It also helps to preserve normal soil nutrient cycling, prevents seed bank formation, reduces disruption to the microbiotic communities of forest soils, and minimizes earthworm populations.
Researchers have observed a resurgence in garlic mustard when competing vegetation is removed during ecosystem restoration. Garlic mustard also thrives with natural disturbances, such as those caused by low land flooding and overbrowsing of native species by deer. If possible, exclude or manage overabundant deer populations in the area, and plant native vegetation in areas where disturbance has occurred.
Only attempt to manage long-standing, dense infestations when a long-term annual commitment to management is possible.
- Remove 90% or more of the site’s flowering plants and rosettes each year.
- Recheck for missed plants during peak flowering weeks. A single large plant can produce over a thousand seeds.
- Revegetate with native species once garlic mustard is under control and the native seed bank is depleted.
While declines have been observed at some long-invaded sites, it is not clear how widespread or enduring these declines will be. Monitor infestations that are not being managed, and if garlic mustard declines, fill the space with native vegetation and monitor for its success to prevent garlic mustard seedlings from filling the opening.
A handy checklist for managing volunteers can be found in the UMN Extension Invasive Species Project Planner document. Provide structure and guidance for volunteer events so that the following conditions are met:
- Be a smart recruiter. The number of volunteers for your event should be suitable to the site and size of the infestation being managed. Garlic mustard pulls are also a great event for all ages.
- Provide training. Make sure volunteers can properly identify garlic mustard and common native species. If using herbicide, train volunteers on safe handling practices.
- Leave no trace. Minimize impacts on natural spaces. Space volunteers far enough apart to prevent trampling of native plants and excessive soil disturbance
- WorkCleanGo. Volunteers should brush all mud and plant materials from their shoes before leaving invaded areas.
Document your work by taking photographs before and after garlic mustard management. Seeing changes can be a great motivation for you to keep working on long-term restoration projects!
Cipollini, D., Rigsby, C. M., & Barto, E. K. (2012). Microbes as targets and mediators of allelopathy in plants. Journal of Chemical Ecology, 38(6), 714-727.
Cosme, M., Fernández, I., Van der Heijden, M. G., & Pieterse, C. M. (2018). Non-mycorrhizal plants: the exceptions that prove the rule. Trends in plant science, 23(7), 577-587.
Durka, W., Bossdorf, O., Prati, D., & Auge, H. (2005). Molecular evidence for multiple introductions of garlic mustard (Alliaria petiolata, Brassicaceae) to North America. Molecular ecology, 14(6), 1697-1706.
Michigan Department of Natural Resources. (2018). Garlic Mustard. Michigan Natural Features Inventory. https://mnfi.anr.msu.edu/invasive-species/GarlicMustardBCP.pdf
Prati, D., & Bossdorf, O. (2004). Allelopathic inhibition of germination by Alliaria petiolata (Brassicaceae). American Journal of Botany, 91(2), 285-288.
Saul, H., Madella, M., Fischer, A., Glykou, A., Hartz, S., & Craig, O. E. (2013). Phytoliths in pottery reveal the use of spice in European prehistoric cuisine. PLoS One, 8(8), e70583.
Reviewed in 2021