The 2021 King County Noxious Weed List, adopted by the Noxious Weed Board at its January meeting, gained two new species and a number of plant name changes. The first addition to the list is a new Class A noxious weed Turkish thistle (Carduus cinereus), an introduced invasive species discovered recently in Oregon and Idaho and not yet known to occur in Washington. Turkish thistle is most likely to be found in rangeland, meadows, pasture, and fields where it competes with native plants and reduces available forage for livestock. Class A noxious weeds have the highest level of priority under the state noxious weed law because of their potential impacts and limited distribution in the state. Early detection and rapid response is the goal for Class A weeds, so please tell your county weed board if you see Turkish thistle in Washington.
The second addition is a new King County Weed of Concern, horse-chestnut (Aesculus hippocastanum), an ornamental tree that has spread beyond gardens and parks into forests where it competes with native plants for space and water. Horse-chestnut fruits are toxic to people but they are attractive to squirrels and other animals who carry them into natural areas. Weeds of Concern aren’t noxious weeds according to the state noxious weed law. They are plants that King County educates residents about due to the plants’ local impacts. People are not required to control Weeds of Concern but they are encouraged to do so where it would be beneficial to ecosystems or agriculture. For more information on the weed list categories, see Weed Lists and Laws.
The other changes to the King County weed list are plant name updates. Because language matters as a way we communicate our values, the King County Weed Board is searching for more inclusive ways to talk about noxious weeds. As an effort in that direction, the Board adopted several name changes that avoid labeling plants as belonging to other countries. The purpose of this effort is to emphasize that the negative impacts of the plants in their new location are the problem, not what country they come from. In fact, many other plants native to the same countries are well-behaved food plants or ornamentals perfectly suited to landscapes and gardens. This process will be done a few plants at a time to reduce confusion with the name changes, and attempts will be made to choose non-national names already in common usage where available.
For 2021, the Board adopted the following common name changes:
Bohemian Knotweed to Hybrid Knotweed (or simply knotweed)
Hybrid knotweed is a hybrid between two other species of knotweed that was first identified in Bohemia, Germany, which is where it got the name Bohemian knotweed (Fallopia X bohemica). It is the most common species of knotweed in Washington.
Japanese Knotweed to Itadori Knotweed (or simply knotweed)
Although this knotweed, Fallopia japonica, isn’t as common in Washington as the hybrid, the name Japanese knotweed is the most familiar to most people. There isn’t another commonly used English name besides Japanese knotweed, so it was decided to use the Japanese name for the plant, itadori, or itadori knotweed.
Brazilian Elodea to Egeria
Brazilian elodea is a confusing name because the plant closely resembles a different water plant native to Washington called Elodea (Elodea canadensis). But Brazilian elodea isn’t an Elodea, but rather an Egeria (Egeria densa).
Canada Thistle to Creeping Thistle
Creeping thistle is the common name of this very common thistle species (Cirsium arvense) in much of the English-speaking world. Also, in spite of the name, it isn’t native to Canada, but rather parts of Europe and Asia. Creeping thistle also accurately describes how this thistle spreads by creeping underground rhizomes.
English Laurel to Cherry Laurel
Cherry laurel is a popular common name for this plant and reflects that it is in the cherry genus Prunus (although cherry laurel is not really a laurel so that is still confusing!). Also cherry laurel is not native to England, but instead to regions bordering the Black Sea in southeastern Europe and northeastern Asia. It is in fact invasive in the British Isles as well as here.
English Hawthorn to Common Hawthorn
Common hawthorn is often used for this species of hawthorn and it is less confusing than English hawthorn which is also used for other hawthorns.
The 2021 King County Weed List also incorporates updates to Latin names made by the Washington State Weed Board to reflect current accepted taxonomy. One of the big updates for plants of interest in King County is the switch from Polygonum to Fallopia for the genus of the three main invasive knotweed species.
Here are all of the scientific name changes for 2021:
- Anchusa arvensis, annual bugloss to Lycopsis arvensis
- Centaurea x moncktonii, meadow knapweed to Centaurea × gerstlaueri
- Polygonum cuspidatum, Japanese (itadori) knotweed to Fallopia japonica
- Polygonum sachalinense, giant knotweed to Fallopia sachalinensis
- Polygonum x bohemicum, Bohemian (hybrid) knotweed to Fallopia × bohemica
- Matricaria perforata, scentless mayweed to Tripleurospermum inodorum
- Saccharum ravennae, Ravenna grass to Tripidium ravennae
- Silene latifolia ssp. alba, white cockle to Silene latifolia
- Zostera japonica, Japanese eelgrass to Nanozostera japonica
Each year, the King County Noxious Weed Board considers changes to the King County weed list as allowed under the State Noxious Weed Law, RCW 17.10. The Board meets regularly throughout the year and welcomes public input on the weed list and the operations of the Noxious Weed Control Program. The Washington State Noxious Weed Board also meets regularly and considers proposals for weed list changes and additions each year. To learn more about participating in the weed listing process, visit the Washington State Weed Board’s web page or email the King County Noxious Weed Program.