Garlic mustard (Alliaria petiolata)

Four-petaled white flowers and slender seed capsules of garlic mustard.

 
 

Garlic mustard (Alliaria petiolata) was likely brought to the United States for food or medicinal purposes in the 1800s. It can be spread by transporting mud that contains its tiny seeds, so it is often found along highly-trafficked trails. Garlic mustard forms thick mats that shade and outcompete native plant species and it can impede natural forest regeneration by producing chemicals that reduce growth of other plants.

Description

Appearance

Garlic mustard has two different appearances depending on whether it is one or two years old. First year plants are a low-growing circular arrangement of kidney-shaped leaves with scalloped edges, called rosettes. In its second year, plants shoot up a 12-36 inch stem that will develop small white flowers at the top. If crushed, the plant smells like garlic.

Leaves and stem

The leaves are kidney-shaped, scallop-edged, dark green, and not noticeably fuzzy or hairy. In its first year, plants are rosettes of leaves. The plant sends up a stalk in its second year. Second year plants have leaves arranged alternate to each other along the stem. Leaves get more triangular in shape the higher up the stem.

Flowers

Flowers are white, small and numerous, with four separate petals. Second year plants can have one or multiple flowering stems. Plants flower from May through June.

Seeds

Plants have slender capsules (called siliques) that are 1-2.5 inches long, each containing a single row of oval black seeds. Each plant can produce hundreds to thousands of seeds that are viable in the soil for five to ten years.

Roots

Plants have a white slender taproot that is "S"-shaped at the top.

Biology

Garlic mustard is an early-season biennial herb that germinates from seed, forms a rosette in the first year, sends up a mature flowering stem the second year, sets seed and dies. Garlic mustard starts to grow in early spring prior to the emergence of native plants, and goes to seed in early summer. Garlic mustard is also allelopathic, producing chemicals that inhibit the growth of other plants and beneficial fungi that help trees grow. Garlic mustard is shade tolerant and is often found covering the forest floor.

Origin and spread

Garlic mustard is native to Europe and was likely brought to the United States for food or medicinal purposes in the 1800s. It is prevalent throughout the eastern and midwestern United States and can be found in areas of the western United States as well. Visit EDDMapS to see current distribution.

Garlic mustard can be spread by transporting mud that contains its tiny seeds. Garlic mustard is often found along trails as humans and animals track mud with seeds along the trail.

Don't be fooled by these look-alikes

There are a number of small flowering plants with similar appearances like native crinkleroot (Cardamine diphylla) and non-native creeping charlie (Glechoma hederacea) however when crushed neither of these lookalikes will smell like garlic.

 
Regulatory classification

Garlic mustard (Alliaria petiolata) is a Minnesota Department of Agriculture Restricted Noxious Weed meaning it is illegal to import, sell, or transport. 

Threat to Minnesota
  • Creates thick mats that shade and outcompete native plant species.
  • Can impede natural forest regeneration by producing chemicals that reduce growth of other plants.
What you should do

One way that invasive plant seeds and fragments can spread is in soil. Sometimes plants are planted purposefully. You can prevent the spread of invasive plants.

PlayCleanGo: Stop Invasive Species in Your Tracks

  • REMOVE plants, animals and mud from boots, gear, pets and vehicle.
  • CLEAN your gear before entering and leaving the recreation site.
  • STAY on designated roads and trails.
  • PLANT non-invasive species.
Native substitutes
 
Control methods

Hand-pulling individual plants is effective if the entire root is removed.  Because flowering garlic mustard can produce seeds even after it's been pulled up by the roots, the Minnesota Department of Agriculture (MDA) recommends that pulled plants be placed in bags for disposal and not simply left on the ground where they were picked. The plants from the bags can be kept on site for burning or piled and covered with a tarp for decay. Be sure to monitor the site and remove any plants that sprout from the burn or decay site. If plants must be moved off site, contact your local yard waste or compost site to see if they are equipped to compost at high enough temperatures to accept noxious weeds at their site. Transportation is only allowed to a disposal site and the MDA requires the load is protected in a manner that prevents the spread of noxious weed propagating parts during transport. It is illegal in Minnesota to dispose of plants in a landfill. See the Minnesota Department of Agriculture noxious weed disposal website for additional information.

Herbicide control can be done using a spot application of 2 percent glyphosate in early spring or late fall when native plants are dormant. This is a systemic herbicide that is taken up by plants and moves within the plant, which can kill leaves, stems, and roots.

Carefully and thoroughly clean off boots, clothes and tools before leaving the area to avoid carrying the tiny seeds to new sites.

Reporting

Report new occurrences by submitting a report through EDDMapS, emailing Report a Pest, calling Report a Pest (1-888-545-6684), or contacting your local county agricultural inspector.

Resources

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