Bull thistle = Cirsium vulgare

A citationed defense of Cirsium vulgare and other thistles is presented on pp289-94 of Timothy Lee Scott's book, "Invasive Plant Medicine, The Ecological Benefits and Healing Abilities of Invasives", available from Amazon http://tinyurl.com/34wf28u or from B&N http://tinyurl.com/3ajl2cr

Scott's book and its citations support a rationale wherein "invasive" plants are helping heal damaged ecosystems.