Effective July 24, the list of prohibited plants in Washington just grew by six. The species added include several popular ornamental plants that are now prohibited from sale: butterfly bush (non-sterile varieties), yellow archangel, lesser celandine and all hybrid non-native hawkweeds, including a type of orange hawkweed that was until very recently still being sold in local stores.
The two other species being added are water plants that are not as well known: Senegal tea plant (Gymnocoronis spilanthoides) and Australian water clover (Marsilea mutica). Non-native invasive aquatic plants are some of the hardest to stop once they are established so prevention is often the only sure way to keep them out of our waterways.
Washington’s quarantine law helps stop the continued introduction of plants that are known to cause serious economic or environmental damage in the state. You can see the whole list on the state’s legislative website.
The Washington State Department of Agriculture’s Nursery Inspection Program is the agency that watches over nurseries in our state and that will be tasked with notifying stores about the new banned species. See their website for more information about who to contact if you see any of these species being sold or to find out more information about the quarantine laws.
Even though some of the banned plants have been very popular and useful in landscaping, they are also highly invasive and difficult to control. The negative impacts far outweigh the positive qualities of these plants in our ecosystems. As the WSDA brochure about the quarantine explains: “Escaped ornamentals are one significant source of infestation. It is often difficult to predict which ornamentals will be invasive and aggressive. Scotch broom, purple loosestrife, and kochia are prime examples of plants which have escaped cultivation and caused enormous economic and environmental damage. The quarantines identify plants known to be invasive and a detriment to the state’s natural resources. These regulations will serve to prevent the continued introduction of these problem plants into Washington.”
You can read more about the state’s noxious weed laws and quarantines on the King County website or the Washington State Noxious Weed Control Board website.