Unraveling Knotweed in the Lower Skykomish
/Habitat Restoration Project Manager Thomas Bulthuis walks through the restoration project.
Highway 2 follows the braids and bends of one of Washington’s most scenic rivers, the Skykomish. This river isn’t just beautiful, the Lower Skykomish River Reach contains some of the best habitat in the Snohomish River Basin for Chinook and other salmonids.
When the people living along the Skykomish River participate in efforts to revitalize the riparian zone—the area bordering the water—they can have a particularly significant impact on salmon. Establishing and maintaining a healthy buffer of native trees and shrubs in the riparian zone shades and cools the water temperature, reduces soil erosion, and supplies large and small pieces of woody debris that provide habitat for salmon, along with other fish, invertebrates, and amphibians.
Just outside of Monroe lies a property on the Skykomish River with a landowner dedicated to stewarding their riparian area. Snohomish Conservation District has been working with this landowner since 2016 and one key aspect of restoring their riparian zone has been controlling non-native, invasive species like knotweed.
Like many other rivers and streams in our region, the Skykomish River has a knotweed problem. When pieces of this non-native, invasive species break off in seasonal floods, they can easily spread downstream and grow into new plants.
Once established, knotweed can exacerbate eroding banks, clog waterways, and prevent native species from establishing and growing into healthy riparian forests. All these factors disrupt the river ecosystem, in turn degrading water quality and negatively impacting the health of our salmon populations.
In order to manage the knotweed on this Skykomish property, our Washington Conservation Corps (WCC) crew applied an aquatic-approved herbicide. With careful consideration for time of year and controlled application of the herbicide, the trained and licensed crew was able to successfully manage the knotweed with less impact than if it had been removed manually, which can result in erosion and require constant maintenance.
Once the knotweed was adequately under control, the WCC crew planted a native forest buffer along 2,900 feet of the Skykomish River to restore the riparian zone. This native vegetation would not have had the space and resources to thrive if knotweed had not been removed beforehand.
Today, eight years after the launch of this project, the knotweed remains under control and the native plants are growing and are on their way to becoming a mighty forest buffer along this critical river.
The success of this project was the result of many key pieces coming together—a landowner committed to restoring riparian habitat on their property, a well-trained and dedicated WCC crew, ongoing funding from the Department of Ecology, and the Conservation Reserve Enhancement Program, a voluntary program that increases salmon habitat by compensating farmers for using salmon-friendly practices in riparian zones.
This project is part of a larger effort by the District, the Tulalip Tribes, Snohomish County, and many other stakeholders in the Lower Skykomish River Basin working to address knotweed in a strategic manner through the Lower Skykomish River Knotweed Management Plan.
The District is dedicated to working with the many partners involved in this project, in particular the willing landowners who are so essential to the success of knotweed management and building a healthy river system.
Established knotweed can exacerbate eroding banks, clog waterways, and prevent native species from growing into healthy riparian forests.
This sapling has protective caging to keep it safe from hungry critters.
This project has been funded wholly or in part by the United States Environmental Protection Agency under an assistance agreement to the Washington State Department of Ecology. The contents of this document do not necessarily reflect the views and policies of the Environmental Protection Agency, nor does the mention of trade names or commercial products constitute endorsement or recommendation for use.
