garlic mustard

Alliaria petiolata

   

Family: Brassicaceae

Weed Class: A

Year Listed: 2000

Native to: Europe, Asia and Northern Africa

Toxic: not known to be

Other Legal Listings: WA Quarantine list, WAC 16-750

additional photos

 

   

Why is it a noxious weed?

It is shade tolerant and is difficult to control once it reaches a site. It is self-fertile and has a high seed production rate. It outcompetes native vegetation with early spring germination and it can establish in a relatively stable forest understory.

How would I identify it?

General Description: Garlic mustard is a biennial to short-lived perennial plant that is garlic scented and can grow to a height of around 3 feet.

Flower Description: Flowers have 4 petals, 4 sepals and 6 stamens. Petals are white, about 1/4 inch long and are twice as long as the sepals.

Leaf Description: Basal leaves are broad with rounded tips and rounded bases (kidney shaped). Upper stem leaves are alternate and triangular. Both leaf types have petioles (leaf stems). Leaf margins are coarsely toothed. New leaves have a strong garlic odor.

Stem Description: Stems are generally upright and one to many can grow from a rosette (cluster of radiating leaves at base of plant). They may be branched or unbranched.

Fruit/Seed Description: Seed pods long and slender, curving upward, up to 2.4 inches long. Seeds are dark brown to black, grooved and oblong in shape. Plants can produce up to 8,000 seeds.

May be confused with:

How does it reproduce?

Garlic mustard reproduces by seed. This plant is capable of cross-pollination as well as self-pollination.
 

Where does it grow?

In Washington State, garlic mustard is found in forested understory areas including urban parks, on roadsides, trails, railroad tracks, streambanks, fields, slopes and floodplains. Within the past couple of years, garlic mustard was found in two counties in eastern Washington. Please click here to see a distribution map of garlic mustard in Washington.
 

How do I control it?

Mechanical Control

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

Cultural Control

Prescribed burning is a control option for large invasions of garlic mustard. Burning is recommended for 2 consecutive years to achieve effective control. Fires must burn hot enough to completely kill plants. If fires are too cool, plants may regenerate from root crowns, producing flower stalks that have higher seed production and result in higher seedling survival.

Biological Control

Several potential biological agents have been researched for the control of garlic mustard. They are Ceutorhyitchus alliariae and C. roberti, shoot-mining weevils that attack rosettes and bolting plants; Ceutorhynchus constrictus larvae destroys seeds; Phyllotreta ochripes, a flea beetle larvae found mining the root and root crown; Ophiomyia alliariae a shoot-mining agromyzid; and a weevil, Ceutorhynchus scrobicollis.

Herbicide Control

Please refer to the PNW Weed Management Handbook, or contact your county noxious weed coordinator.


 

For more information

 
See our Written Findings for more information about garlic mustard (Alliaria petiolata).
See our postcard for early detection information about garlic mustard (Alliaria petiolata).
Plant Conservation Alliance's Alien Plant Working Group page on garlic mustard
King County Noxious Weed Control Board's garlic mustard information
Report on garlic mustard from the book "Weed Control in Natural Areas in the Western United States"

Additional Photos


 
 

 


Garlic mustard with seed pods

 


Young garlic mustard plants

 


Nipplewort on left and garlic mustard on right

 


Garlic mustard leaf on left and nipplewort leaf on right

 


Garlic mustard seed pods

 


Garlic mustard stem leaf

 


Garlic mustard infestation

 


over-wintering rosette

 


mature seed pods (siliques)

 


beginning to bloom

 


infestation

 


in bloom and forming siliques

 


pulled small plants in bloom

 


s-shaped root

 


large rosette leaf

    

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