Garlic mustard (Alliaria petiolata) is a high-priority invasive species in Illinois. Large infestations of this low-growing herbaceous flowering plant limit growth and productivity of native plants and threaten the long-term health of forests limiting how we enjoy them now and in the future.
Explore more about garlic mustard by downloading these information sheets: Introductory Level | Comprehensive Information
Garlic mustard is native to Europe and was first recorded in North America in 1868. This potherb was historically eaten in early spring when few greens were available. It was first reported in Illinois in 1918 and by the late 1980s was recognized as a problem species. It has been reported in at least 70 of Illinois’ 102 counties.
Eight states have declared this invasive as a prohibited or noxious weed. Illinois does not currently mandate or regulate it.
Garlic mustard’s early spring growth can quickly cover the forest understory. Infestations form a monoculture that competes with native plants for light, water, and nutrients. This threatens wildflowers, tree seedlings, insects, wildlife, and future forests. Large populations reduce nutrients in the soil and release allelopathic compounds that slow the growth of other plants.
Infestations impact the ecosystem and reduce the ability to harvest timber, hunt, collect mushrooms, enjoy spring wildflowers, watch birds, and spend quality time in beautiful, healthy forests.
Garlic mustard is commonly found in shaded and semi-shaded woodlands. Make it a habit to look for invasive species whenever in the woods. Monitor for garlic mustard along pathways of entry such as forest edges, creeks, trails, and in disturbed areas. Mark plant locations with a map app or flags.
Garlic mustard has a two-year, or biennial, growth cycle. First- and second-year plants will grow together and in large infestations will rotate dominance in the landscape every other year. Garlic mustard is easiest to identify in spring when second-year plants are flowering. Explore photos of each stage of growth at the end of the page.
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Southern Illinois | Northern Illinois |
|---|---|---|
| Flowering | Starts early April | Starts mid-April |
| Seeds Form | May |
Mid-April to June |
| Seeds Release | Late May | Starts mid-June |
Seeds require a cold dormant period, or stratification, of at least 8 months. Most seeds germinate in spring, as early as February, with some continuing through fall. Seeds can survive in the soil up to 10 years.
Plants grow into multi-stalked clusters of low-growing basal rosettes. Leaves are kidney-shaped with rounded scalloped edges that smell like garlic when crushed. The plant will overwinter as a basal rosette. First-year plants can easily be overlooked at low levels.
In the early spring, basal rosettes will have a surge of growth as they bolt and bloom. The flowering stalk is 1- to 4-feet tall with triangular, toothed-edged leaves. Its flowers have four white petals. Seeds form in upright seed pods known as siliques.
As plants die, they dry and release an average of 360 black seeds in early summer. Large plants can produce more than 8,000 seeds. Clusters of dead dry stalks will likely have first-year germinates nearby.
Garlic mustard is a high-priority invasive plant that harms native forest ecosystems in Illinois. The first step to removing it is finding it. - Own a forest? Always keep an eye out for garlic mustard along creeks, forest edges, and trails. Identification: Garlic mustard grows over two years....
Removing garlic mustard is a multi-year process that focuses on preventing at least 90% of plants from producing seeds to prevent spread. Be prepared to manage annually for at least five years to deplete the seed bank and plan for long-term monitoring to prevent reinvasions. Sporadic management can make infestations worse.
No management method is entirely effective. Before treatment, develop a long-term strategy that considers available time and labor resources, as well as the infestation size and location.
Land managers face competing obligations; prioritizing sites for management is important for success. For help prioritizing sites, explore a management decision tree in the Midwest Invasive Plant Network’s Garlic Mustard Guide.
In Illinois, there is a 6- to 8-week window in the spring to control second-year plants before they produce seed. Do not attempt removal if plants are dry and seeds are falling out; this will further its spread.
Garlic mustard is a high-priority invasive plant that harms native forest ecosystems in Illinois. The key to keeping it from taking over your woodland is early detection and rapid response.
Garlic mustard is a high-priority invasive plant that harms native forest ecosystems in Illinois. Completely removing garlic mustard requires several strategic approaches over several years.
Prescribed burns can be paired with hand-pulling plants and chemical control to manage...
Garlic mustard is a high-priority invasive plant that harms native forest ecosystems in Illinois. Completely removing it takes several strategic approaches over a series of years.
Chemical control can be paired with hand-pulling plants and prescribed burns to manage large infestations....
Garlic mustard is a high-priority invasive plant that harms native forest ecosystems in Illinois. Completely removing garlic mustard requires several strategic approaches over several years.
Prescribed burns in fire-tolerant forest communities can be paired with hand-pulling plants and...
Remove plants after they bolt and before flowering.
These shallow-rooted plants are easy to pull from the soil once they bolt. Pulling is labor intensive and may only be practical for small infestations or if a lot of people are available. Grasp the stalks at the base and gently tug to remove the S-shaped root. Plants with flowers or fruit should be put in bags. Leave tied bags in the sun for several days to kill the seeds. The plant material can be thrown away, burned, or composted at a commercial facility. Home composting is not recommended as the pile may not reach the temperatures necessary render any seeds unviable.
Consider hosting a garlic mustard pull volunteer event for sites that would otherwise be damaged by herbicide or prescribed burn control. Explore resources in the How to Host a Garlic Mustard Pull Toolkit.
This method works for large populations of bolting plants. Cut stalks at ground level to eliminate seed production. Stalks with siliques can still form viable seed.
In forest communities adapted to fire, a prescribed burn can help control large infestations and stimulate native plant growth. Always follow state and local regulations and safety protocols. Managers need an approved plan and a permit from the Illinois EPA. Explore an Introduction to Prescribed Fire and more resources for implementing a prescribed fire.
A mid-intensity burn in the spring is most effective. A handheld propane torch can also be used for spot treatments. Fire will remove leaf litter and prompt seeds to germinate. You can treat the new seedlings with herbicide to deplete the seed bank faster.
Herbicide can be a low-cost, low-labor option for large infestations. Always read and follow product labels before use. Avoid impacting desirable plants with herbicide overspray. Apply enough herbicide to wet foliage, but not so much that it drips off.
Anyone who applies pesticide on public lands must be licensed. Learn more from the Pesticide Safety Education Program.
Use products with Glyphosate or Triclopyr to treat basal rosettes and bolting plants. Apply in early spring or fall. Late applications, during or after flowering, can reduce viable seed production but are not entirely effective.
White-tailed deer move seed and avoid eating garlic mustard, so infestations can increase herbivory pressure on native plants. This can reduce native plant abundance and allow garlic mustard to increase in dominance. Exclude or manage large deer populations when removing garlic mustard.
Researchers continue to explore if European aphids that feed on garlic mustard can be used for control.
Long-term monitoring has provided some evidence that long-standing garlic mustard populations, at least 50 years old, may be self limiting and could decline without management. These findings are not well supported.
Garlic mustard is a high-priority invasive plant that harms native forest ecosystems in Illinois. Researchers from University of Illinois and University of Wisconsin collaborated to test at what growth stage herbicides can be used on garlic mustard and still stop the plants from producing viable...
Midwestern researchers recently explored the time frame needed to apply herbicides in order to prevent seed production.
Results: Applying Glyphosate and Triclopyr during the flowering stage reduces viable seed production. This was not 100% effective, so do not use this as a primary method to control garlic mustard. This gives land managers an extra 2 to 3 weeks to apply herbicide to garlic mustard in the spring.
