The Biology of Canadian weeds. 144. Pastinaca sativa L.

Cain, N., Darbyshire, S. J., Francis, A., Nurse, R. E. and Simard, M.-J. 2010. The Biology of Canadian weeds. 144. Pastinaca sativa L. Can. J. PlantSci. 90: 217-240. The parsnip, Pastinaca sativa, was introduced to North America shortly after European settlement as an important root-crop. It subsequently escaped cultivation and naturalized as a less palatable "wild" form. Cultivation of parsnip has diminished in Canada to the point where it is now only a minor crop, but the wild form has increased as a troublesome weed, particularly in eastern regions. Wild parsnip is most prevalent in eastern Canada and the northeastern United States, but occurs across the continent except in the far north and extreme southeast. As a monocarpic biennial with a large tap root, it reproduces entirely by seed. A wide variety of habitats and soil types are tolerated. It is considered a noxious weed because of its toxic properties (primarily photo-activated dermatitis) to both humans and livestock. It invades disturbed sites, rights-of-way, pastures, perennial crops, and reduced-tillage fields where it effectively out-competes shorter vegetation. In arable fields, wild parsnip is normally controlled by tillage. Manual removal, cutting, and mowing can be effective in reducing seed production, but direct contact with plants or sap is hazardous. Various herbicides have been reported to be useful in the control of wild parsnip (e.g., glyphosate, 2,4-D, triclopyr, etc.), but little quantitative information is available on application rates and levels of control.