The Biology of Canadian Weeds. 146. Lapsana communis L. Ardath Francis1, Stephen J. Darbyshire1, David R. Clements2, and Antonio DiTommaso3 1Agriculture and Agri-Food Canada, Eastern Cereal and Oilseed Research Centre, Wm. Saunders Bldg. #49, Ottawa, Ontario, Canada KIA 0C6 (e-mail:
[email protected]); 2Biology Department, Trinity Western University, 7600 Glover Road, Langley, British Columbia, Canada V2Y 1Y1; and 3Department of Crop and Soil Sciences, 903 Bradfield Hall, Cornell University, Ithaca, NY 14853 USA. Received 17 August 2010, accepted 20 December 2010. 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: 553Á569. 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.