Distribution
Giant hogweed is native to the Caucasus mountains of southwest Asia. It was first brought to North America in the early 1900s. It is now locally established in the northeastern US and adjacent Canada (USDA-NRCS 2004), including southeastern Ontario, where it has now become locally common (Morton 1978). It has been reported as far west as Ohio, Michigan, and (barely) Wisconsin (USDA-APHIS 2004, S. Trull, pers. comm.), as well as in Oregon, Washington, and British Columbia (Dawe and White 1979, USDA-NRCS 2004).
Giant hogweed has reappeared at a number of new sites in Lower Michigan, western Upper Michigan, and adjacent northeast Wisconsin, as plantings or recent escapes from plantings (USDA-APHIS 2004, S. Trull, pers. comm.). It is likely to continue to show up in new locations, assisted by horticulturalists and gardeners looking for something unusual to plant.
Michigan
Minnesota
For More Information
Wisconsin Background Maps (UW - Stevens Point)