Outer bracts at the base of flower head with 1 to 2 mm long spine tips and inner bracts without spines. Crowds out native species and forage for livestock (Zouhar 2002) Skip to main content. Scotch thistle is a Class B noxious weed and control is required in King County. It can invade most any disturbed habitat and grow in dense thickets. The objective of this guide is to aid ... Canada thistle Cirsium arvense (l.) Scop. A species profile for Musk Thistle. Contact the Forest Service . Many insects feed on the leaves, stems, flowers and seeds, while some songbirds also feed on thistle seeds. 2005. Non-native noxious weeds destroy biological diversity, decrease forage, increase erosion potential, and decrease land values … Stems have large spiny wings that form from leaf bases that run down stems. This species is also on the Washington quarantine list (known as the prohibited plants list) and it is prohibited to transport, buy, sell, offer for sale, or to distribute plants or plant parts, seeds in packets, blends or "wildflower mixes" of this species, into or within the state of Washington. Many noxious weeds such as knapweeds, leafy spurge, and Scotch thistle can convert rangeland and grassland, which contain a rich array of native grasses and wildflowers, into monocultures that are less palatable for grazing animals. They have 6 to 10 spine-tipped lobes and tapered leaf bases forming winged leaf stalks. Weed class: A In the lands that I manage, I only control Canada thistle. It can grow up to 8 feet tall and 5 feet wide, with small pink-purple flowers. It poses an economic threat to the agriculture industry by reducing crop yields. For more information, see Noxious Weed Lists and Laws or visit the website of the Washington State Noxious Weed Control Board . Because control is not required in the county, it is on the list of Non-Regulated Noxious Weeds for King County. It germinates in the fall, then overwinters as a rosette (a radiating cluster of leaves) and produces flowering stalks in late spring. The plant forms dark pink to purple, globe-shaped flower heads, 1-2 inches in diameter, which stand alone on branch tips and bloom July-October. Leaves are oblong and prickly with toothed margins. Thistles belong to a large plant family and are mostly native to Asia and Europe. 2005. Leaves are oblong and prickly with toothed margins. Six months later we heard that the weed laws had been rewritten. Other Common Names: Winged Plumeless Thistle This plant is listed by the U.S. federal government or a state. In late 2018, we had an opportunity to give native thistles a boost in Iowa by urging changes to state noxious weeds code. Italian thistle, Carduus pycnocephalus, is similar but it generally has fewer flowerheads (1-5), than slenderflower thistle, Carduus tenuiflorus (5-20 flowerheads). Questions: contact Steve Van Vleet or phone (509) 397-6290. Habitat: Moist meadows, clearings, forest openings usually at middle to high elevations Bloom time: Spring to summer Range: Cascades to Coast in Washington to Central British Columbia When competing with the dense growth of other ungrazed pasture plants, slenderflower thistle may grow soft and etiolated (white from a lack of chlorophyll). An official website of the United States government. See our Written Findings for more information about Slenderflower thistle (Carduus tenuiflorus). Stems grow up to around 6.5 feet and are unbranched to branched and plants are covered in loose, woolly hairs. The plant lists are managed as a joint project of the Washington Native Plant Society and the University of Washington Herbarium at … Yellow starthistle provides poor and potentially damaging forage to cattle, and may poison or kill horses that ingest large quantities over short periods of time. ... State law here in Wisconsin to control the non-native Canada thistle. Browse for native plants, landscape plans, plant photos and create your personal printable shopping list at our Native Plant Guide. Find out how. Spreng.) Class C Washington State Noxious Weed. It is toxic to livestock. Russian thistle plants break off at the base after maturity and tumble with the wind, scattering seeds over great distances. Join the community of plant enthusiasts, whether you are a botanist, hobbyist, parent, or gardener. Why Should I Care? Washington Invasive Species Council. It is considered an invasive weed as it forms dense stands in pastures and rangelands making it difficult to control. ex Willd.) ... Washington State Noxious Weed … Stems are coarse with many spines, and are gray-green and highly branched. Center for Invasive Species and Ecosystem Health, Washington State Noxious Weed Control Board, Columbia Basin Cooperative Weed Management Area, Invasive Species Research, Control, and Policy Forums, Washington’s Urban Forest Pest Readiness Plan, Lake Roosevelt Invasive Mussel Rapid Response Exercise, Scotch Broom Ecology and Management Symposium, Steve Dewey, Utah State Univ., Bugwood.org, Steve Hurst, USDA NRCS PLANTS Database, Bugwood.org. Flowerheads are clustered in groups of 5 to 20+ at branch tips. Scotch thistle invades disturbed areas, such as roadsides, ditch banks, pastures (especially when overgrazed), campgrounds, and burned areas. ... On this page they show a Canadian thistle brought to Washington by settlers in the 1800s that they are fighting hard to … Most biennial thistle species around the state are from the non-native Carduus genus. Many of the species listed within the new Iowa brochure … The Canada thistle bears 1/8-inch long “fruits” that are flattened and brownish with a circle of long hairs. It’s found in dense stands along roadsides, waste areas, pastures are invaded from roadside populations, ditches and disturbed areas. These prickles are an adaptation that protects the plant from being eaten by herbivores.Typically, an involucre with a clasping shape similar to a cup or urn subtends each of a … Restore and maintain healthy native plant communities. Larvae impact Canada thistle (and other thistle) seed production by feeding within developing buds and preventing seed formation. Scotch thistle also is listed as a Class B noxious weed in Washington, meaning it is designated for control in certain state regions. We wish to thank all the WNPS members and others who have enjoyed Washington's flora and took the time to create plant lists for many special places. State of Washington. Displace Native Species and Reduce Biodiversity. Milk thistle occurs on fertile lands of improved pastures that have been overgrazed and poorly managed. Olympia, WA 98504-2560, Washington State Noxious Weed Control Board. Turkish thistle's native habitat stretches from Turkey east to the Himalayas. It can reduce yield and quality of crops. Food. State noxious weed list and schedule of monetary penalties, Chapter 16-750 (24 May 2006). Once established, it spreads quickly replacing native plants. Questions: contact Steve Van Vleet or phone (509) 397-6290. Scotch thistle is on Washington’s Terrestrial Noxious Weed Seed and Plant Quarantine list, meaning it is prohibited to transport, buy, sell, offer for sale, or distribute Scotch thistle plants, plant parts, or seeds (Washington Administrative Code 16-752-610). Washington Native Plant Society. Scotch thistle may be distinguished from all other thistles by the dense, white, woolly covering on its stems and leaves. It is 0.16 to 0.20 inches (4 to 5 mm.) The life cycle of the American goldfinch (Spinus tristis), Iowa’s state bird, is intertwined with native thistles. Why Is It a Noxious Weed? Unfortunately, this plant with a delicate name and flower can escape gardens and aggressively colonize elsewhere. Slenderflower thistle invades pastures, meadows, and fields, displacing native and/or beneficial forage species. Promoting native and desired species also should help slow the spread of Scotch thistle. Photo credits included in pdf. Milk thistle is a Class A noxious weed in Washington State and eradication is required. Is this Weed Toxic? Deferring sheep grazing until autumn has been effective in reducing stand density. Washington Administrative Code. It is not enforced to my knowledge. Its dense stands compete with native plants for resources and can form a physical barrier to water and grazing for animals. Please see WAC 16-752 for more information on the quarantine list.