Photos from King County.gov
Before treatment (2015)
Post treatment (2016)
Knotweed before and after treatment on the South Fork Skykomish River (2015 and 2016).
A Look at Watershed-Scale Knotweed Management King County Noxious Weeds Control Program
The mission of the Noxious Weed Control Program is to provide benefits to the environment, recreation, public health and economic resources of King County by preventing and minimizing harmful impacts of noxious weeds. The King County Noxious Weed Control Program in Washington State has a multi-year grant-funded approach to knotweed management within target watersheds. It consolidates management and monitoring into Cooperative Weed Management Areas that are multi-jurisdictional projects on public, private and tribal lands. The program works with the Port of Seattle and all 39 cities and towns within King County to achieve comprehensive coordinated noxious weed control across all local jurisdictions.
Infestations by Property Types Percent of sites in each category
In 2019, the program surveyed for knotweed on 105 river miles and has reduced the net area of knotweed on rivers by 73 percent since 2015, from 16.4 to 4.5 acres (net acres means the area covered if the knotweed plants were all combined in one place instead of spread out over 154 acres). Private landowners who own riparian areas are key to the success of the project. They can voluntarily give permission for their land to be included in the program. This approach has been effective in starting knotweed management high in the watershed then working downstream to limit the vegetative spread of the plant into treated areas. The success of the program occurs by treating private properties since they make up half of the sites in the watershed with infestations (King County Noxious Weed Control Program).
A PLACE FOR TREES - FURTHER CONSIDERATIONS | 93
