Location of knotweed control projects
There are approximately 19.5 acres of knotweed in the municipal watershed. We are controlling the smaller patches, totaling 4.5 acres, by covering to starve the roots. The larger patches could not logistically be treated with covering. In 2010 the Seattle City Council passed an ordinance allowing limited use of the herbicide imazapyr through 2012 to treat these remaining large patches. In 2010, 7.72 acres were treated for the first time. In 2011, 7.70 acres were treated for the first time, plus the 7.72 acres treated in 2010 were re-treated. Of the 15.42 acres, only 1.94 acres are on land that drains into the Cedar River.
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