Francis, A., Darbyshire, S. J., Clements, D. R. and DiTommaso, A. 2011. The Biology of Canadian Weeds. 146. Lapsana communis L. Can. J. Plant Sci. 91: 553-569. Nipplewort, Lapsana communis, is an annual weed of the Asteraceae native to Europe and western Asia, first detected in northeastern and Pacific northwestern regions of North America in the 19th century. It appears to have been introduced as a contaminant of imported garden material and seeds, but may also have been deliberately introduced as a medicinal herb. After a century of remaining close to its original points of introduction in gardens and ruderal habitats, it spread to neighbouring areas, and now occurs across southern Canada and in many areas of the United States. Possible reasons for this range expansion include forest clearance and changing crop management practices as was observed in Europe, where this plant has become an important weed in grain, forage and vegetable crops. In Ontario, L. communis has recently emerged as a weed in wheat (Triticum aestivum), corn (Zea mays) and soybean (Glycine max) fields. Various herbicides have been effective on L. communis in corn, but control has been less effective in winter wheat, where the herbicides MCPA and 2,4-D used alone have provided little or no control. Control in soybean has yet to be assessed. In Europe both mechanical methods and herbicides have been effective in controlling the weed, but L. communis has recently developed tolerance to MCPA. It is unclear whether this weed will continue to spread or will remain a localized or relatively minor crop pest in Canada.