Butterflybush is an introduced garden shrub from northwestern China and Japan that is now escaped and naturalized in the USA (CA, CT, GA, HI, IL, KY, MA, MD, MI, NC, NJ, NY, OH, OR, PA, SC, TN, VA, WA, WV) and Canada (BC) (
USDA 2010). In BC, it is found naturalized in the southwestern part of the province, on southeastern Vancouver Island and in the Fraser Valley. Recent observation has shown spread in the Chilliwack area, including the Chilliwack River and Vedder Canal, as well as along Highway 99 part way to Squamish. It is readily visible and abundant along roadsides when in flower (mid-July to mid-September). Northward spread is temperature limited (tolerant to between -15C and -20C). Efforts to control spread in the Fraser Valley are underway, with some removal in 2009 and inventory to document the extent of spread along the Chilliwack River ongoing (Jeanne Hughes, Fraser Valley Invasive Plant Council, pers. com. 2010).
