Garlic Mustard Emerges in Spring

Weed watchers beware: spring is a critical time for the emergence of invasive species in northwest Oregon! During the spring months, these intruders can take advantage of ample sunlight, water, nutrients and space to establish themselves where they are not wanted. But upcoming Weed Watcher Workshops in Washington County can prepare you to help. Find more information about these workshops below or at


Garlic mustard has been trying to take up residence in Washington County during the last few years, but the Tualatin Soil and Water Conservation District wants you to help keep this invader from settling in for the long haul. The weed is of greatest concern in woodland areas, although it has been identified along road rights-of-way, trails, and streams. Whatever the location, it dominates the area by displacing native vegetation and reducing plant diversity.


Why is it a problem?


Clean Water Services, a partner in this invasive species education and eradication effort, notes that Garlic Mustard has no known natural enemies in North America, is self-fertile, and is difficult to eradicate once established. It is one of just a few herbaceous species that invades and dominates the understory of forested areas. In doing so, it appears to alter habitat suitability for native birds, mammals, and amphibians, and may affect populations of these species.


You can identify garlic mustard fairly easily during this time of year:

•             Garlic mustard has a two-year lifecycle, which means that you may spot it in two forms. During the first year, garlic mustard appears to be about a foot tall with kidney-shaped scalloped leaves in a basal rosette (this is botany speak for leaves that form near the base of plant arranged like the petals of a rose).

•             During the second year, this invader takes on a more upright form, with the flower stalk elongated – all the better to spread its seed! When it has bolted in this manner, the plant can reach 4 feet in height.

•             The leaves will be sharply toothed and triangular in shape, arranged in an alternate on the stem.


•             When you crush these leaves, they emit a strong garlic odor.

•             If you catch this plant now, you will notice small white flowers with four petals through May.


The Oregon Department of Agriculture has more good identification tips in its garlic mustard brochure  as well.


What if you find garlic mustard?


If you encounter this invader, you can take immediate action as well as report it. To remove the immediate culprit, pull plant the before it goes to seed in late May, being sure to remove entire root. All captured plants should be bagged to prevent re-sprouting. Mowing is ill-advised as it may help spread rather than eradicate the plant by disbursing the seed. Keep in mind that these tiny seeds love to cling to boots, pants and vehicles, all of which should be well brushed or cleaned after contact.

But you aren’t alone in the fight against garlic mustard. Clean Water Services of Washington County is hot on the case as well. You can report sightings to their Invasive Species Coordinator by calling  (503) 681-3600 or emailing

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