invasive.org: "V. bonariensis is native to South America. It has escaped cultivation and become naturalized in disturbed areas across the SE United States and in California. It is drought and heat tolerant and very common along roadsides and in other disturbed areas. V. bonariensis is very similar to V. montevidensis and V. incompta, and all three are invasive species." In Massachusetts so far it has been found in the wild in only two western counties (Hampshire and Hampden). See also http://www.nwcb.wa.gov/detail.asp?weed=165 (monitor list, Washington State)