thornton creek

Thornton Creek Alliance and partners King County, Seattle Parks, Seattle Public Utilities, the City of Shoreline, Earthcorps, and Forterra, convened in fall of 2017 to discuss a coordinated effort to control knotweed in the Thornton Creek Watershed. The parties completed a strategic plan in 2018, with the Thornton Creek Alliance leading the charge in mapping knotweed and other noxious weeds in the watershed.

Twin Ponds, Thornton Creek, Forterra
Noxious weeds like knotweed are introduced species that spread aggressively and contribute to stream bank erosion. They crowd out vegetation that benefits fish and wildlife and can reduce property values. Left uncontrolled, these weeds have the potential to further spread and create infestations along the entire creek. Winter floods and upstream disturbances can bring new infestations to stream banks, even if these weeds have not been present in the past.

what is knotweed and why control it?

Knotweed (polygonum spp.) is a bamboo-like, non-native plant that wreaks havoc on properties and ecosystems. Once established, knotweed forms dense stands that crowd out native vegetation and clog small waterways, increasing bank erosion and lowering the quality of riparian habitat for fish and wildlife. Knotweed treatment typically takes several years to be successful.


Forterra worked with private landowners and public partners to control knotweed along and restore healthy ecosystems within this highly urbanized watershed.



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