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| Wild Parsnip in flower. |
Wild parsnip (Pastinaca sativa) is an aggressive Eurasian member of the carrot family (Apiaceae). It grows in sunny areas and will tolerate dry to wet soil types. It is found along highways, in disturbed fields or meadows, lining farmed fields, invading prairie ecosystems, or in disturbed, un-landscaped portions of new subdivisions.
Each year, a number of Wisconsin landscape crews, rural homeowners and green industry professionals conducting prairie restoration activities have a painful introduction to this plant. Contact with sap from the wild parsnip can cause phytophotodermatitis, a light sensitive reaction on your skin. If the juice from broken stalks, leaves or flowers contacts your skin and then is exposed to sunlight, a skin rash will result 24-48 hours later. Symptoms range from slightly reddened skin to large blisters. The affected area and blisters may produce a sensation similar to a mild to severe sunburn or a stinging, burning sensation. The blisters and ‘burned patches’ do not spread or itch, as poison ivy rashes do, but they are uncomfortable and leave brown scars that can last anywhere from a number of months to two years.
Regrettably, wild parsnip is not well known in the medical community. Symptoms may be mistaken for a severe case of poison ivy. Treatment is based on the severity of the ‘burns’. Treatments may include cool wet dressings, topical steroids or nonsteroidal anti-inflammatory drugs. Severe cases may require systemic steroids. See your doctor if you develop symptoms.
Fortunately, wild parsnip is easy to identify, and thereby, avoid. At maturity, the plant reaches 4-5 feet tall. It bears many large flat clusters of yellow-green flowers on a thick stalk. Flowers appear from the first of June through July in southern Wisconsin. Seeds begin to form around the end of July. The plant will often have both flowers and seedpods on it at the same time. Seeds are flat, oval, yellow-green and about the size of a sunflower seed. The plants have a rosette of basal leaves as well as stem leaves. Both sets of leaves are pinnately compound, ovate and have heavily toothed margins. Stem leaves are arranged alternately on the stem (versus an opposite arrangement). After flowering and producing seeds, the plant begins to brown and die.
Wild parsnip can be confused with prairie parsley, an endangered native species in Wisconsin. Prairie parsley has sparse, light yellow flowers, and oblong pinnately compound leaves with few teeth. However, it is very unlikely that the endangered prairie parsley will be growing on most job sites, and all too likely that wild parsnip will be.
Wild parsnip has been in the state for many, many years, but it has become much more common fairly recently. It is not easy to control, so the best strategy is to prevent its entry into an area if at all possible. When the plant is first detected in an area, it can be cut below ground level with a sharp shovel. Wear long sleeves, long pants and gloves when conducting control measures. Rural homeowners may be able to work after sunset so that exposure to sunlight does not occur.
Wild parsnip can be pulled by hand, if you wear protective gloves. If the population is fairly large, you may use a brush-cutter just after peak bloom and before seed set. Be careful not to get any wild parsnip juice adhering to the machinery on your skin. Remove all the cut material (wear gloves). A few weeks later, repeat the treatment to prevent plants that re-sprouted from flowering. Treatments will probably need to be repeated over several years. Herbicides containing the active ingredient glyphosate are also effective against wild parsnip. In high quality natural areas such as prairies, the Department of Natural Resources recommends burning the site and then applying spot treatments of a 1-3% glyphosate solution to wild parsnip rosettes as they re-sprout after burning.
– Lisa Johnson, UWEX Horticulture Agent, Dane County
