Garlic Mustard

Fact SheetAlliaria petiolata

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Identification

Appearance

Alliaria petiolata is an herbaceous, biennial forb. First year plants are basal rosettes which bolt and flower in the second year. Plants can be easily recognized by a garlic odor that is present when any part of the plant is crushed.

Foliage

Foliage on first-year rosettes is green, heart-shaped, 1-6 inches long leaves. Foliage becomes more triangular and strongly toothed as the plant matures.

Flowers

Second-year plants produce a 1-4 feet tall flowering stalk. Each flower has four small, white petals in the early spring.

Fruit

Mature seeds are shiny black and produced in erect, slender green pods which turn pale brown when mature.

Biology

Origin

Garlic mustard was originally brought to the United States from Europe during colonial times as an early spring edible. It's tasty, garlicky flavored leaves make a fantastic pesto and great addition to soups. Help control garlic mustard by harvesting it in the spring and using it for culinary adventures.

Habitat

Abandoned Field, Agricultural Field, Edge, Open Disturbed Area, Pasture, Railroad Right-of-Way, Roadside, Utility Right-of-Way, Vacant Lot, Yard or Garden. Euphorbia cyparissias is most often found in old fields and natural grasslands.

Life cycle

Beginning in May (in the mid-Atlantic Coast Plain region), seeds are produced in erect, slender pods and become shiny black when mature. By late June, when most garlic mustard plants have died, they can be recognized only by the erect stalks of dry, pale brown seedpods that remain, and may hold viable seed, through the summer.

Ecological Threat

Alliaria petiolata is an aggressive invader of wooded areas throughout the eastern and middle United States. A high shade tolerance allows this plant to invade high quality, mature woodlands, where it can form dense stands. These stands not only shade out native understory flora but also produce allelopathic compounds that inhibit seed germination of other species. Alliaria petiolata is native to Europe and was first introduced during the 1800s for medicinal and culinary purposes.

Management Options

This species is Quarantined: Class B Noxious Weed

Treatment concerns

Garlic mustard roots secrete chemicals that inhibit growth of other nearby plants and may disrupt mycorrhizal associations.
Because of the high risk of spread by seeds, treatments are most effective before the plants go to seed.
Garlic mustard can self-pollinate, is a prolific seeder, and seeds can persist in the soil for over 10 years.
Contain and solarize all removed plant material after treatment as seeds can develop even after the plant is pulled

General Guidance

Some locally-evolved plants may out-compete garlic mustard when planted at unusually high densities following initial treatments.
Basal rosettes experience high over winter mortality rates, making second year plants in the spring a better target for treatment if resources are limited.
Most methodologies alone will not suffice and should be part of an integrated pest management plan.
Which methods you choose also depend on the purpose of control: eradication (removal of all plants, plant parts, and seed bank), or containment (reducing seed production, reducing spread, reducing growth, removing individual plants near site of concern).
All action promotes disturbance - mechanical, chemical, and even just doing nothing. Our work is in figuring out how to minimize disturbance and maximize positive benefits.
The intent of mechanical or chemical treatment is to kill target plants.
Management options listed below are representative of research by institutions like The Nature Conservancy, Michigan State University Extension, Midwest Invasive Plant Network, and the Ontario Invasive Plant Council.
Here are additional guidance documents on best management practices for garlic mustard
Michigan State University Extension Summary on Garlic Mustard
Midwest Invasive Plant Network Overview for Managers on Garlic Mustard, 2021
Ontario Invasive Plant Council Best Management Practices for Garlic Mustard

Summary of Mechanical Treatment Options

Mechanical treatment can sometimes cause greater disturbance than if the site was left alone or if another treatment option was utilized.
If pulling or digging, remember that soil disturbance can encourage growth from seed bank.

text in a table describing mechanical treatments for Garlic Mustard

Summary of Chemical Treatment Options

Be careful not to damage or kill nearby desirable plants when conducting management work.
Always read and follow pesticide label directions. Application of pesticides may require a certification from the Agency of Agriculture, Food and Markets. The Agency website provides information on what applicator certification is needed.
If a treatment for a specific species isn’t listed on a given product, don’t use it.
Product labels may require you to check Endangered Species Protection Bulletins. Learn more about protection bulletins here.
Understand the risk of, and how to avoid, drift.
The timing of some chemical treatments may overlap with when certain plants are flowering, and, in order to protect pollinators, herbicides should not be applied when plants are flowering. To mitigate the risk, consider utilizing an integrated pest management plan, such as cutting the plants to set back flowering time, and then applying pesticides in the lowest effective volume.
Chemical treatments pose a risk to plants, animals, and humans, but can be used in ways that greatly reduce this risk, and provide a solution to otherwise hopeless scenarios.
For questions regarding the appropriate chemical to use for a particular situation, or general information on pesticide safety, ingredients, and more, contact the Vermont Agency of Agriculture, Food & Markets’ Pesticide Program.
For questions about certification and continuing education credit opportunities, contact the Vermont Agency of Agriculture, Food & Markets’ Pesticide Program.
For questions about additional training opportunities, contact the UVM Extension Pesticide Safety Education Program.
Special permits are required to apply herbicides in a wetland. Contact Vermont Department of Environmental Conservation’s Wetlands Section for more information.
Herbicides cannot be applied within 200 feet of a Public Water Source Protection Area unless the Water Supply Division is notified. Call 1-800-823-6500 for more information. Similar requirements may be in place for proximity to private water sources.
Forests that are certified organic or adjacent to organically certified agricultural lands may carry restrictions regarding chemical application. Check with the Northeast Organic Farming Agency of Vermont for more information.
The National Pesticide Information Center provides objective, science-based information about pesticides. Check out their website for more information or call 1-800-858-7378.

text in a table describing chemical treatments for Garlic Mustard

Biocontrol

There are four weevils that seem to feed exclusively on garlic mustard. Testing is ongoing to see if they can be used for biocontrol.
Most animals avoid eating garlic mustard; Some livestock, like goats, may be trained to graze on it which may help reduce seed production but won’t get the roots of the plant.