The purpose of this paper is to document the spread of Dyssodia papposa (Asteraceae; Fetid Dogweed) along roadsides in eastern Canada. Fetid Dogweed is reported new to the provinces of Manitoba and Québec, Canada, and has greatly expanded its range along southern Ontario highways in the past 15 years. It is expected to continue to expand in northeastern North America. The distinctive appearance of this plant combined with earlier botanical fieldwork along Ontario highways makes it highly unlikely that this species was previously overlooked.