Claviceps spp. It is adapted to a wide range of soil conditions, and spreads vigorously by wind-borne seeds and by way of its extensive, creeping root system. Canada thistle is a creeping perennial that reproduces from vegetative buds in its root system and from seed. It is difficult to control because its extensive root system allows it to recover from control attempts. Canada thistle was such a problem that it caused the Canadians to write first weed eradication law in North America: the Canada Thistle Eradication Act of 1865. The Canada thistle is a perennial species of flowering plant in the Asteraceae family. According to Dr. Harris Steinman, an allergy expert from South Africa, "Russian thistle can cause dermatitis in persons who come into direct contact with it. This highly invasive thistle prevents the coexistence of other plant species through shading, competition for soil resources and possibly through the release of chemical toxins poisonous to other plants. Not Your Average Thistle Clematis spp. Ontario Weeds Act - noxious; Other provinces - noxious in AB, BC, SK, MB, and QC; Canadian Federal Seeds Act - Class 3 ; U.S. Federal Noxious Weed - no Cirsium arvense (CANADA THISTLE); plant may contain toxic levels of nitrates. Scientific Name: Cirsium arvense (L.) Scop (ITIS) Common Name: Canada thistle, Californian thistle, Canadian thistle, creeping thistle, field thistle, corn thistle, perennial thistle, field thistle. Spotted Knapweed 80. Combining control methods is the best form of Canada thistle management. This thistle is also commonly known as the creeping thistle and field thistle. The dermatitis appears to be due only to mechanical irritation from plant floral bracts, which pierce the skin and stimulate an urticarial reaction." Hoary Cress 55. Canada thistle, flowers in South Dakota - Photo by Chris Evans; University of Illinois. It is native throughout Europe and northern Asia, and widely introduced elsewhere. (ERGOT); an ascomycetous fungus which grows on small grain (e.g., rye); also contains the alkaloid indole. Leafy Spurge 59. Canada Thistle 42. BLM Northwest Regional Noxious … One of the reasons it has been so successful all over the world is that it can reproduce from both seeds and roots. Yellow Starthistle 65. Managing Canada Thistle Canada thistle (Cirsium arvense) is a perennial that has plagued farmers in America since European settlement, and is a Noxious Weed in Pennsylvania. NebGuide: Canada thistle (CIAR4) OK-OSU Extension-Thistles and their Identification (CIAR4) Ohio State University: Identifying noxious weeds (CIAR4) Purdue University: Control practices for Canada thistle (CIAR4) The Nature Conservancy: Wildland Weeds Management & Research Program (CIAR4) UC Davis, IPM: abstract & images (CIAR4) Canada thistle develops seed sparingly and may produce 1,000 to 1,500 seeds per flowering shoot. 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