Biological data are provided for Alliaria petiolata (M. Bieb.) Cavara and Grande (garlic mustard). This weed is found in Victoria, British Columbia, in the St. Lawrence valley of Quebec and in Southern Ontario where it attains maximum abundance in Middlesex County. It is most commonly found in shaded sites: in deciduous woodlands, under hedges and in gardens. When crushed, the aboveground parts exude a strong odor of garlic.