Washington State Weeds

Garlic Mustard

Garlic Mustard

Alliaria petiolata • Class A

Family Name: Brassicaceae family  (brass-ih-KAY-see-ee)
Common: Cabbage family (formerly Cruciferae)
Genus: Alliaria (al-ee-AR-ee-uh)
Meaning: Of the Allium(Latin for garlic) family
Species: petiolata (pet-ee-oh-LAH-tuh)
Meaning: Has leaf stalks (petioles)
Description:

Seedlings develop into basal rosettes by mid-summer. The plants overwinter as a basal rosette with kidney-shaped leaves. When the plants bolt in early spring, the mature leaves are triangular, becoming smaller toward the top of the plant, leaf margins are coarsely toothed. In early spring the roots and new leaves smell like garlic. Each plant usually produces one flowering stem that is about 3 feet tall bearing small, white 4 petaled flowers about one fourth inch long. Seed pods are long, slender, and curved upward, bearing dark brown/black seeds that are grooved and oblong. Roots typically have an S-shaped bend that helps the plant hold on to the soil. 


 Why Is it a Noxious Weed?

Garlic mustard is difficult to control once it has reached a site; it can cross-pollinate or self-pollinate and has a high seed production rate.  It outcompetes native vegetation and is sun and shade tolerant. 


Where Does it Grow?

Garlic mustard is competitive in a wide range of soils, sun, shade and moisture. It is often found in open disturbed lands, fence rows, shaded roadsides, riparian areas, flood plains, along hiking trails and in dry sunny areas along railroads.  It can establish in dense shade, like the forest understory areas, in addition to urban parks and sunny sites. 


Facts:

In addition to its ability to  cross-pollinate or self-pollinate and high seed production rate, if a plant is cut or stepped on, many new stems will emerge from the root stock.

It is also allelopathic, producing chemicals that inhibit to growth of surrounding plants including mycorrhizal fungi, which is necessary for healthy tree growth and tree seedling survival.  Seeds can last in the soil for at least 10 years.


Control Options:

Hand pulling is an effective method and mature plants are easily pulled, although care must be taken to remove all of the roots. 

  • Controlled burning is also an option for large infestations. This method is recommended for two consecutive years in order to achieve effective control. The fire must be hot enough to completely kill the entire plant or plants may regenerate from the root crowns and produce stalks that have a higher than normal seed production, which will result in and even higher seedling survival. 

  • Herbicides have been shown to be effective. Spot spraying with an herbicide containing the active ingredient glyphosate (e.g.: Roundup Pro®, Glyfos®, etc.) or 2, 4 D plus dicamba (e.g.: Weedmaster®, etc.) Be aware that glyphosate is non-selective and will injure any plants that it comes in contact with, including grass, whereas, 2, 4 D is selective. Herbicides should be applied in spring and fall. .

  • When using herbicides, read and follow all label instructions and obey all label precautions. (Note: pesticide product registration is renewed annually and product names and formulations may vary from year to year.)  


More Information:

 Download our Flyer or visit Washington State Noxious Weed Control Board Here. Photo by Leo Michels

 


More Pictures:  

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