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Thistles (Cirsium spp.) 

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Thistles are truly unpleasant plants to have around and the most obnoxious specimens are exotic species that readily invade native habitats.  The three worst species are bull thistle (C.vulgare), European swamp thistle (C. palustre), and Canada thistle (C. arvense).  Note that "Canada" thistle is not an exotic from Canada, it's from the Mediterranean region.  Bull and European swamp thistle are bienniels, meaning they flower once every two years.  A little glyphosate herbicide readily eliminates the first-year rosettes.  Failing that, it's rather fun to go "thistle-whacking" on those nice summer days when the tall flower heads are present.  A good machete will prevent the plants from forming seed and reduce the amount of seed floating across the landscape.   However, be careful not to kill our native species, especially Pitcher's thistle (C. pitcheri) found along the Great Lakes sand dunes.  It's on Michigan's "threatened" plant list.

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daisy_button_blue_md_wht.gif  Return to the Purple Flower Page, or to the Michigan Invasive Plant Council home page.

This website is maintained by Bill Cook in cahoots with the Michigan Invasive Plant Council (MIPC).  The MIPC is a loose group of folks (not necessarily a group of loose folks!) working to make information available about invasive plants in Michigan and related issues.  If you have questions or comments about the information on this page, contact Bill

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