Knotweed, an invasive weed, is by no means new to the Island or the area, and is the target of some pretty extensive outreach and treatment programs by both the Washington State and King County Noxious Weed Programs.

Knotweed is very commonly found along river systems in Western Washington, but unfortunately, it also pops up in a host of other spots, explained city natural resources specialist, Alaine Sommargren.

The city has been  working on eradicating patches for several years. The city has begun to map and mark patches particularly along roadsides, where patches are often mowed or cut during the growing season. The problem is that by mowing or digging the plant, fragments of the plant are scattered – which leads to new or larger patches, she said. The sign is an effort to both encourage folks to leave the plant alone (until the city is ready to treat it) and also get the word out about this noxious and aggressive weed.

City crews will be treating mapped knotweed sites in mid to late summer, when knotweed is starting to slow down growth and go dormant for the winter. This is the most effective time to apply herbicide. In general, they use a very targeted approach, injecting a small amount of an aquatic formulation of glyphosate directly into the stem, so that nearby plants aren’t harmed.

The city will be posting information about the knotweed program on its website in the next couple weeks, with resources for homeowners who wish to take on knotweed on their own property. There will also be a presentation by the King County Noxious Weed Program, for homeowners.

To find out more, contact the city’s natural resources specialist Alaine Sommargren at 206-275-7879 or visit www.kingcounty.gov/environment/animalsAndPlants/noxious-weeds/weed-identification/invasive-knotweeds.aspx.