Who would’ve thought that a plant named after two foods could be such a problem.
Garlic mustard (Alliaria petiolata) is a priority noxious weed and a true outlier within Jackson and Josephine counties in comparison to the rest of the state of Oregon. It was first discovered in Southern Oregon on the mainstem of the Rogue River fifteen years ago, which then spurred containment, control, and eradication efforts across the watershed. While it has been quite the battle, noxious weeds experts and herbicide applicators have found fewer plants in 2025 and anticipate seeing even fewer in 2026. Regardless, treatment efforts within the two counties will continue as of late February through early May, thanks in large part to funding that has been awarded from the Oregon State Weed Board (OSWB). To date, containment goals have been achieved, with no outlier populations detected in ten years and no other Southern Oregon waterways being impacted by garlic mustard.
However, we need your help keeping an eye out for it, so you need to know what to look (and smell) for! Leaves and stems emit an onion or garlic smell when trampled or crushed, and plants can range in height between 12 and 48 inches tall. First-year plants are a rosette of 3 or 4 kidney-shaped, scallop-edged leaves. Second-year plants generally produce one or two flowering stems with numerous white flowers that have four separate petals forming a cross. The plant produces black, oblong seeds in 1 to 2 ½ inch slender pods called siliques that radiate from the stem just below the flowers. Its slender taproot is “s”-shaped at the top.
Garlic mustard does have native doppelgangers, so you will have to make sure that you have made all of the above observations before removing the plant or treating it with herbicide. It is found in forest understory or edges, in shaded roadsides, urban areas, riparian areas, along hiking trails, and on agricultural lands. Garlic mustard is an aggressively growing plant that will create a monoculture wherever it establishes itself, altering forest communities. Since garlic mustard has no known natural enemies, is self-fertile, and is difficult to eliminate, the most effective control method is to prevent its initial establishment. Burning, herbicides, and/or cutting are often used to control large existing populations. Very recently, a biocontrol agent has been approved for release in the United States. Currently in Oregon, there are populations of garlic mustard in Portland, the Columbia Gorge, and parts of the Rogue Valley.
What can you do if you come across garlic mustard? After accurately identifying it, you can hand-pull and bag it, or spray small patches, and document the site (locations, photos, dates, treatment type(s) using the Oregon Invasive Species Hotline and notifying your local cooperative weed management area (CWMA) coordinator. If you’re located in Jackson or Josephine County, report your findings to Amie Siedlecki, Jackson + Josephine Counties CWMA Coordinator: asiedlecki@rvcog.org and/or Carri Pirosko, Noxious Weeds Specialist for the Oregon Department of Agriculture: carri.pirosko@oda.oregon.gov.
More information and resources can be found here.
