History
This Class A noxious weed has a very limited distribution in Washington, and control and eradication are required in King County. Most of the known infestations in Washington are from King County, and the majority of sites are on City of Seattle Parks property. If you think you see this plant, please contact our program.

First identified in Seattle in 1999 and listed as a Class A noxious weed in 2000, the King County Noxious Weed Program is working closely with landowners to prevent new infestations and eradicate existing infestations. Without cooperation we will lose the battle to keep garlic mustard out of woodland areas throughout western Washington.

Impacts
Garlic mustard is an invasive non-native biennial herb that spreads by seed. It is difficult to control once it has reached a site; it can cross-pollinate or self-pollinate, it has a high seed production rate, it out competes native vegetation and it can establish in a relatively stable forest understory. It can grow in dense shade or sunny sites. The fact that it is self fertile means that one plant can occupy a site and produce a seed bank. Plant stands can produce more than 62,000 seeds per square meter to quickly out compete local flora, changing the structure of plant communities on the forest floor. Garlic mustard is considered allelopathic, producing chemicals that inhibit the growth of other plants and mychorrizal fungi.

Biology and Morphology
Garlic mustard is a biennial herb that grows to about 3 feet tall. The small, white 4-petaled flowers appear in early spring and seed production soon follows. 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. In early spring the roots and new leaves smell like garlic. Each plant usually produces one flowering stem. If a plant is cut or stepped on, many stems will form.

Prevention is the recommended control option. Familiarize yourself with the flower, the plant and the habitat where it grows. Monitor sites regularly to remove plants prior to seed set.

Garlic mustard photos - click thumbnail for larger image

For information on garlic mustard identification and control, please download our garlic mustard weed alert (1.02 MB) Acrobat file). For in-depth information on impacts, biology, identification and control of garlic mustard in King County, please read the garlic mustard best management practices (294 KB Acrobat file, 43 seconds on 56K modem).

If you find garlic mustard in King County, please notify us through our online infestation form.

To find out where we have records of this weed in King County, use our interactive noxious weed map and search for garlic mustard.

For more information about garlic mustard, please see the written findings of the WA State Noxious Weed Control Board.

Read an informational bulletin about garlic mustard (282 KB Acrobat file, 41 seconds on 56K modem).

Read garlic mustard-related press .