Noxious Weeds Blog

King County’s 2018 Noxious Weed List to be set at January 24 Weed Board Meeting

Spotted jewelweed (Impatiens capensis) is on the Washington State Noxious Weed List. It is native to eastern United States but invasive on the West Coast where it was introduced.

The public is invited to join the King County Noxious Weed Control Board for King County’s annual weed list hearing, where the Board will hear public comments, review proposed weed list changes, and set the official 2018 King County Noxious Weed List. The hearing will be held on January 24, 3:30 pm at the Mercer Island Library, large conference room, 4400 88th Ave SE, Mercer Island, WA. Following the hearing, the Weed Board will hold its regular monthly meeting, which is also open to the public (see the Weed Board web page for more information). The Board welcomes public input at all meetings.

You might wonder why King County holds an annual weed list hearing, so here is some background information on the weed list process in Washington, and a sneak peak at some of the new weeds being added this year.

Washington’s Noxious Weed Law shares the job of noxious weed prioritization between the state and the county weed boards. The State Noxious Weed Control Board sets the list of noxious weeds for all of Washington, and then the county weed boards fine tune the state list based on local goals, impacts and resources (see King County Weed Board for more info on our Board).

More precisely, the state determines the Class A list that all counties must require control of, and designates certain Class B weeds for each county that they also must require property owners to control, mostly based on distribution of the species. Then the counties can select additional Class B and C weeds from the state list to regulate, or choose to educate about any listed or non-listed species that are important for that county.

Now for the sneak peak of new species. For 2018, the state added several new species that are of significant concern to King County. There are two new jewelweeds on the state list. Spotted jewelweed (Impatiens capensis) is already well-established in King County and will likely be a target for increased education and recommended control, but not required control.

Spotted jewelweed (Impatiens capensis) is invasive in the Pacific Northwest and negatively impacts native plants and habitat, and is on the Washington State Noxious Weed List. However, it is native to the eastern United States, where it is a beneficial species.

Spotted jewelweed (Impatiens capensis) is a prolific seeder and can rapidly fill in open spaces created by natural or human made disturbances, such as this restoration site covered in a carpet of spotted jewelweed seedlings. Photo by Warren Gold.

The other species, small-flowered jewelweed (Impatiens parviflora), is very new to the state and only known in a couple of locations, both in King County. This new Class A noxious weed will be a high priority for King County to locate and get controlled quickly before it spreads.

Small-flowered jewelweed (Impatiens parviflora) is a European species that has shown up recently in King County and has been added to state noxious weed list. Photo by Alexander Wright.

Small-flowered jewelweed (Impatiens parviflora) is shorter than the other invasive Impatiens species. It may have a broader tolerance and be more invasive in dry, shady sites than the others. Photo by Alexander Wright.

The other major new noxious weed that is a serious concern for King County is European coltsfoot (Tussilago farfara). There are already several known infestations of this new Class B noxious weed in the county, at least two of which are on upper Snoqualmie River tributaries, and it appears to be spreading through flooding and soil disturbance, much like invasive knotweed does. This species will be a high priority for both detection and control due to its potential serious impact in riparian habitats. It is designated for required control by the state so it will be added to the regulated Class B list for King County.

European coltsfoot (Tussilago farfara) flowers come up before the leaves in the spring. They resemble aster flowers but are bright yellow. Photo by Matt Below.

European coltsfoot (Tussilago farfara) leaves are visible in the summer and somewhat resemble native coltsfoot in overall growth form, but are only shallowly lobed along the edges. Photo by Sasha Shaw.

For more information on these and other new state listed species, see the Washington State Noxious Weed Board What’s New page.

You may be wondering why the noxious weed law requires control of some noxious weeds and not others. For the most part, control is only required for noxious weeds that are still limited enough in distribution to allow for effective containment and eradication. For example, the highly dangerous Class A noxious weed giant hogweed has been reduced to only a few hundred, relatively small locations in King County, making it feasible to work towards eradication.

For species that are more widespread, but that are a high priority for county residents, control may also be required, but the goal is to reduce impact and prevent spread, and not necessarily eradicate it, since that would be very difficult and costly. For instance, the King County Noxious Weed Control Board has selected tansy ragwort for required control in King County in past years due to its impact on livestock and hay production.

For even more widespread noxious weeds, the Board encourages control through education and technical assistance. Two examples of widespread noxious weeds are English ivy and Scotch broom.

While these two introduced plants can significantly affect habitat, they are too widespread for county-wide control, so the county board instead focuses on outreach and education, encouraging control where feasible and teaching effective control methods.

For more information on the King County weed list and the Washington state noxious weed law, visit www.kingcounty.gov/weeds under “Weed Lists and Laws,” or contact Sasha Shaw.