June 22, 2007 When people hear the word "parsnip" they usually think about a root vegetable roasted with beef, or included in a hearty soup. But for natural resource professionals, "wild parsnip" means an invasive plant that can cause blisters on arms or legs while they work outdoors.
"The wild parsnip population along Iowa's roadsides, pastures and abandoned fields is very heavy across Iowa and the Midwest this year and people should avoid it just like poison ivy," said John Walkowiak, forester and land protection leader with the Iowa Department of Natural Resources.
Wild parsnip, Pastinaca sativa, a native of Eurasia is an erect herbaceous plant related to the carrot family growing three to four feet in height. At this time of year, wild parsnip bears hundreds of small yellow flowers, which produce large round yellow seeds.
"Wild parsnip grows in disturbed areas ranging from dry to wet prairies, savanna openings and especially along roadsides. Once an infestation begins, it spreads across an area to form dense stands that are difficult to control," Walkowiak said.
Wild parsnip contains chemicals in the leaves, stems, and flowers that can cause intense, localized skin burning or rashes and even blisters. "It appears that contacting wild parsnip sap increases the skin's sensitivity to sunlight giving a dermatitis like burn, some people call a false or artificial sunburn that can last for several months," he said. "When walking in areas where wild parsnip exists, people should wear gloves, long pants and a long sleeved shirt to avoid contact."
If contact has occurred and causes blisters, it is best cover the affected area with cool, wet cloth, avoid letting the blisters rupture by keeping the area clean and applying antibiotic creams or powders. For serious cases consult your doctor.
"Control of wild parsnip is difficult and requires good timing and persistence," Walkowiak said. To control a small amount of wild parsnip, cut the root one to two inches below the ground with a sharp shovel before the flowering begins. Cutting the plants before they flower in April or May can be successful, but the parsnip may resprout.
"Natural resources land managers find the use of selected herbicides (glyphosate or triclopyr) in the late winter or early spring shows the best results and avoids skin contact with wild parsnip. Using prescribed fire does not harm the plants as it simply re-sprouts," Walkowiak said.
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