King County Weed Board approves noxious weed list for 2018

cover image of the 2018 King County Noxious Weed List
The 2018 King County Weed List has a few new species, including the one on the cover, European coltsfoot, a new Class B noxious weed in Washington.

The 2018 King County Noxious Weed List is official now! The King County Noxious Weed Board set the annual list at its January meeting, adding the new state-listed species and renewing county priorities to educate and require control of other selected weeds impacting our county. See our earlier story for information and photos of some of the new species.

Here’s a summary of the changes (with links to photos and information on the State Weed Board website):

  1. Small flowered jewelweed (Impatiens parviflora), new Class A noxious weed, regulated and known to occur in King County
  2. European coltsfoot (Tussilago farfara), new Class B noxious weed, regulated and known to occur in King County
  3. Malta starthistle (Centaurea melitensis), new Class B noxious weed, regulated but not known to occur in King County
  4. Spotted jewelweed (Impatiens capensis), new Class C noxious weed, not regulated and very widespread in King County
  5. Eurasian watermilfoil hybrid (Myriophyllum spicatum x. M. sibiricum), new Class C noxious weed, not regulated and probably occurs in King County
  6. Non-native cattail species and hybrids (Typha angustifolia, T. domingensis, and T. x glauca (and any other nonnative Typha spp.), new Class C, not regulated and known to occur in King County (was previously added to state list but just added this year to the county list to help property owners control it on lakeshores)
  7. Spurge flax (Thymelaea passerina), removed from Class A list and taken off of King County’s list due to there being little chance of impact or occurrence in the county

In addition to these changes, the King County Weed Board elected to continue requiring control of tansy ragwort (Senecio jacobaea), absinth wormwood (Artemisia absinthium) and buffalobur (Solanum rostratum) throughout the county due to the concern of farmers about the impacts of these noxious weeds.

The Board also renewed the limited requirement for controlling invasive knotweed (Polygonum spp.) along the riversides of the Cedar River outside of Renton and the Green River above Auburn city limits. As before, this requirement is dependent on King County or program partners providing knotweed control services in the selected area for affected private land landowners who request assistance. And finally, the Board also renewed the requirement for control of Scotch broom (Cytisus scoparius) along I-90 right-of-way east of mile 34 and on Highway 2 within King County boundaries.

And of course there are many more noxious weeds on the King County list. These are just a few of the changes and local selections for required control. Check out the whole list online or click here to download a printable version of the 2018 King County Noxious Weed List brochure.

For more information, visit the King County website or the Washington State Weed Board website, or contact the Noxious Weed Program directly at

Now let’s go get those pesky weeds!

small-flowered jewelweed growing along a road
Roadside infestation of small-flowered jewelweed that King County staff will return to this year to see how effective control efforts were last year. Wish us luck! Photo by Matt Below.


  1. Cat tail? Would you believe that many years ago, we had almost no cat tail here? I don’t know why. It just did not do very well for many years. Now, we might make it our town flower (for Los Gatos). Pussy willow is another option, but is neither native nor culturally significant.

    • We have a native cattail species that is really common and considered a positive part of the environment, but the non-native narrow leaf and a hybrid are starting to show up and are now on the noxious weed list. It’s true that some people dislike even the native cattail since it can be a bit overwhelming, but our noxious weed law just allow targeting of non-native plants so they are out of luck at least for this purpose. Aren’t some species of willow native down where you are? I think they all collectively called pussy willow but I could be mistaken. Thanks for reading and commenting!

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