Skip to main content
King County logo

Project overview

Map of the Cedar River Knotweed Control Project

Started in 2007 in response to significant landowner concern, this project is jointly implemented by King County Noxious Weed Control Program (KCNWCP) and Forterra, who works as the restoration coordinator for Seattle Public Utilities (SPU). Although the work is closely coordinated, Forterra manages the knotweed control work on the lower portion of the river from the Renton Limits up to approximately Highway 18, and KCNWCP manages the work on the upper portion above Highway 18 to the Cedar River Watershed boundary. Support and advocacy for this project is provided by the Friends of the Cedar River Watershed (FCRW) and major partners for this project also include King County Parks and the King County River and Floodplain Management.

Project area (download map file)

The project area managed by Forterra extends from River Mile 6 (approximately the Renton City Limits) up to River Mile 11.7 (Lower Lions Natural Area) and KCNWCP manages the project area above River Mile 11.7 up to River Mile 22, beginning below Landsburg Rd., and includes Big Bend Natural Area and neighborhood, Penninsula Natural Area, the Rock Creek Wetland, Dorre Don Natural Area and neighborhood, Maple Valley Grange, and the mouth of Taylor Creek.

Tributaries covered in the project area include Rock Creek, Peterson Creek and Taylor Creek (only the lower portion of Taylor Creek is known to have knotweed).

News and updates

In 2014, KCNWCP presented a poster summarizing the Stewardship in Action (SiA) project on the Cedar River, including work of our partners Forterra, Seattle Public Utilities and many others. The poster can be downloaded by clicking the image below.  

Cedar River Poster 2014 UW Conference

In the 2012 field season, KCNWCP re-treated all known sites between River Mile 11.8 and 22. Forterra re-treated sites that were initially controlled in 2010 and 2011. Forterra is working with the City of Renton and the Friends of the Cedar River Watershed to begin treatment of knotweed on the river within the City of Renton city limits.  Forterra/SPU and KCNWCP both have secure funding for this project through the end of 2013 and are pursuing funding to continue the project beyond that date.

Need more information or want to get your property included? Contact us at


Cedar River knotweed at Dorre Don levee site
Cedar River knotweed control
Cedar River knotweed control at Elkinton - Dorre Don replanting


  • King Conservation District (King County)
  • National Fish and Wildlife Foundation (King County)
  • Environmental Protection Agency (Forterra/SPU)