There was a recent article entitled something like, "Every species was invasive once." Seemed to me to be a very useful rationalization for all the alien plants included here. And here's another one. This Eurasian isn't nearly the problem that it's spotted relative is, and it would be a stretch to call it invasive at least in Michigan. This is a very variable species, and there is great variation in botanical opinions of which plants are included in the species. That makes it almost impossible to know where it occurs, or where it was actually a different plant. USDA says brown knapweed has been reported from CA, CT, DE, IA, ID, IL, IN, KY, MA, MD, ME, MI, MT, NC, NH, NJ, NY, OH, OR, PA, RI, UT, VA, VT, WA, WI, WV, BC, NB, ON, QC, and GL. Monroe Co MI, 9/8/15.