The Washington State Noxious Weed Control Board is considering several significant changes for next year’s state noxious weed list. These include adding small-flowered jewelweed (Impatiens parviflora) and European coltsfoot (Tussilago farfara) as Class A and B noxious weeds, respectively—additions originally proposed by the King County Noxious Weed Control Program.
Small-flowered jewelweed is a widespread invasive annual in Europe, native to parts of Asia, that was recently discovered in Washington. It often grows in shady areas like forests, riverbanks, and also disturbed or cultivated sites. The plant is usually 1 to 3 feet tall and has tiny, pale yellow flowers, each with a short, straight spur. Like other Impatiens, this plant reproduces through seeds that rocket out of their seed pods when touched (hence another of the plant’s common names, “small-flowered touch-me-not”). There are currently only two known small-flowered jewelweed sites in Washington State, both in King County. One location is near the Woodland Park Zoo in Seattle and the other is east of Redmond in northeast King County.
European coltsfoot is a low-growing creeping perennial that grows in disturbed areas such as flood plains and roadsides, especially those with wet soils. It spreads by branched rhizomes that break readily, forming new clones, and by fluffy, dandelion-like seeds that spread in the wind. The flowers emerge on bare stems before the leaves, with each stem producing one yellow aster-type flower. The large, flat leaves emerge from the rhizomes around the time when the flowers go to seed. Although it is similar to Washington’s native sweet coltsfoot (Petasites frigidus var. palmatus), European coltsfoot has yellow flowers instead of white and the leaves aren’t deeply lobed. European coltsfoot is only known to occur in a few locations in western Washington, according to the Washington State Noxious Weed Control Board. One of the larger known infestations in King County is at Three Forks Natural Area on the Snoqualmie River.
Both plants are currently on the state’s monitor list.
The board is also considering proposals to add spotted jewelweed (Impatiens capensis), hybrid watermilfoil (Myriophyllum spicatum x Myriophyllum sibiricum), and cheatgrass (Bromus tectorum) as Class C noxious weeds.
Spotted jewelweed is a 2- to 5-foot-tall hairless annual that grows in “forests, lake and pond edges, riverbanks, sloughs, disturbed wetlands and sunny roadside ditches or canals,” preferring wetter soils at low elevations. Its leaves have rounded teeth and grow alternate on the stems. 1-inch-long orange flowers (rarely white or pale yellow) usually have red or orange spots. Like small-flowered jewelweed, spotted jewelweed spreads by seeds that explode out of their pods when touched. Spotted jewelweed is already widespread in western Washington and is having a significant impact on many King County creeks such as Thornton Creek, Kelsey Creek, and Cottage Lake Creek among others.
Hybrid watermilfoil is a cross between the invasive Eurasian watermilfoil (Myriophyllum spicatum) and native northern watermilfoil (Myriophyllum sibiricum). Watermilfoil is very difficult to identify to species and often requires DNA testing to be certain, partly because of its tendency to hybridize and because of how variable the plants are in different conditions.
Cheatgrass, also called downy brome, is well known as an invasive grass in the western United States. It is a 1- to 2-foot-tall annual grass native to the Mediterranean region. It has invaded a wide variety of ecosystems throughout the United States, but is a particular problem in parts of the west where it dominates open rangeland, creating problems for livestock and wildlife and increasing fire frequency and intensity. This plant reproduces by seed.
You can find more information on these and other changes being proposed to the noxious weed list at the Washington State Noxious Weed Board’s “What’s New” page. For more information on exactly what “Class A, B, and C” mean, visit our website.
The State Weed Board welcomes comments about the proposed changes. You can submit written testimony regarding these proposed changes by email to noxiousweeds@agr.wa.gov, by mail to WSNWCB, P.O. Box 42560, Olympia WA 98504-2560 by Monday, October 30, or by attending the public hearing on October 31 at 1:00 p.m. at the Coast Conference Center in Wenatchee.
Sources: All plant information for this article comes from the Washington State Noxious Weed Control Board website, except that for cheatgrass. Cheatgrass information comes from articles by Oregon State University and the U.S. Forest Service.
Spotted jewel weed is a favorite of our native Anna’s Hummingbirds.
Hi Laurie,
Thank you for your comment. Plant invasions are complex and often there are benefits as well as negative impacts to the invasive plants we are targeting. The goal is to find ways to reduce the negative impacts where they outweigh the benefits, and hopefully find ways to mitigate against the loss of the benefits where we can. One way to do that might be to replace the non-native spotted jewelweed with native species that also benefit hummingbirds, or even to find other non-native species that are beneficial but less invasive.
Spotted jewelweed is a particularly challenging case. You’re right that it is popular with hummingbirds, and is in fact an important plant for hummingbirds in its native range in the eastern United States. However, in the Pacific Northwest, spotted jewelweed isn’t native but was introduced starting in about the 1950’s and has spread considerably since then on its own. Where it has spread along streams and other habitats, it is displacing PNW native plants including a similar species of jewelweed called Impatiens ecornuta, which it is also hybridizing with. I think it would be great for people who remove spotted jewelweed to plant native species that are beneficial to hummingbirds. However, the overall negative impacts of spotted jewelweed are significant enough that it should be removed where it is invading into native habitat areas.
What’s the point of identifying a weed that can only be id’d with DNA testing?
Great question! It does make it challenging for sure. Fortunately there are some ID characters that help us narrow down which species a plant could be, and then the DNA test allows us to distinguish between very similar plants, as with the milfoil species. However, we don’t expect everyone to be able to do this. If someone notices a plant creating an impact, for instance an aquatic weed taking over in a lake, we ask them to contact us so we can send an expert to narrow down which plants could be causing the problem.