Meet the experts working to stop invasive garlic mustard in the Willamette Valley

Sarah Hamilton spends her days knocking on doors, visiting lands and helping people learn about native plants. But her most important mission is stopping harmful weeds from spreading.

As a native and invasive plants specialist with Marion Soil and Water Conservation District, Hamilton is among the professions who lead the fight against invasive species in the mid-Willamette Valley — especially garlic mustard, a small plant that can have very harmful effects on biodiversity. 

“I’ve seen how impactful garlic mustard is. It’s a small plant. It doesn’t look like it would be something to be too concerned about, until you’ve seen it really take off,” Hamilton said. It has especially impacted biodiversity in forests on the East Coast and is increasingly becoming a problem in other Oregon counties, she said.

Through education, outreach and data gathering, Hamilton is helping landowners recognize the threat and keeping their ecosystems healthy.

Originally from Europe and Asia, garlic mustard is a noxious weed that is very difficult to control, Hamilton said. It’s allelopathic, which means that it can release chemicals to the soil that affect the growth, reproduction, or survival of other organisms. It is also very resistant to the sun and the shade, and can spread very quickly in different terrains.

The first of two sightings in Marion County was around a year ago. Authorities continue to track the development of the plant, said Brandin Hilbrandt, the executive director of the North Santiam Watershed Council. His organization also does conservation work, especially in the northern area of the Santiam River. 

“With the recent fires, (garlic mustard) poses a high risk of spreading quickly and outcompeting native plants that are working hard to regrow,” Hilbrandt said. 

It could also increase the risk of destabilizing slopes and raising the amount of sediment in local streams and rivers, which in the long term may compromise drinking water supplies and aquatic habitats, he said.

The plant has not been reported near Salem but it is still important to continue prevention work to avoid it from spreading, Hamilton said. She recommends not driving off track and cleaning shoes and tires to avoid unknowingly spreading invasive seeds.

“Left unchecked, dense garlic‑mustard infestations could turn today’s inexpensive hand pulling into years of costly herbicide programs like those now burdening the Portland area and Mount Hood,” Hilbrandt said.

Conservation efforts

Apart from preventing the spread of invasive plants, Hamilton works to “make people excited” about native plants through native plant sales, outreach and workshops, she said. 

Native plants are crucial for supporting biodiversity, providing habitat and food for wildlife and maintaining healthy ecosystems. They also offer benefits like water conservation, erosion control and reduced need for pesticides and fertilizers. 

Hamilton has been working with the Marion Soil and Water Conservation District for around 10 years. A graduate of Oregon State University, she has specialized in forest ecology, owls and horticulture throughout her career.

She was an intern at several conservation districts in Oregon before her current position. “I fell in love with the work that the conservation districts are doing,” she said. 

The Marion Soil and Water Conservation District supports rural and urban landowners with invasive species control, irrigation, manure and waste management, erosion control, and habitat restoration, Hamilton said. 

The district has eight full-time employees and plans to hire an urban planner. It also runs the Little Habitat Project, which guides and certifies landowners on improving their habitats, and hosts workshops, educational events and projects such as the native plant sales Hamilton manages.

The Marion Soil and Water Conservation District is one of many created after the Dust Bowl in the 1930s and 1940s, which was marked by intense droughts and dust storms in several parts of the country, Hamilton said. It is nonregulatory, which means that all landowners work with Hamilton voluntarily. 

The North Santiam Watershed Council, Hilbrandt’s organization, does similar work, often in collaboration with the Department of Agriculture, tribal partners, local governments and other organizations. It hosts regular events for volunteers to pull weeds and help conservation efforts. The most recent group managed to pull over 95 pounds of garlic mustard before they generated seeds, he said.

Hamilton’s daily work can vary greatly. Some days she is called to do site visits and gather information about invasive plants, while others she provides information on how to best prevent their spread and keep spaces healthy. 

She also works on landscape-level projects to address the spread of other invasive species like ludwigia and garden yellow loosestrife, both of which are present in the area.

One of the challenges Hamilton experiences the most is getting the information about where invasive plants are. 

“It can be hard to collect all that information without me going out and surveying every property, and I don’t have the capacity to do that,” Hamilton said. “It would be great to have more of the public involved in learning what invasive species are on their property, which ones might be high priority and how to report them.”

To report weeds, people can call the Oregon Invasives Hotline, which shares the data with Hamilton, Hilbrandt and other invasive plant professionals statewide.

Contact reporter Alan Cohen: [email protected].

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