Wild parsnip, is a plant that grows along the side of roadways and in open areas, including gardens. It probably looks familiar.
It causes “phyto-photodermatitis:” Its sap plus sunlight will make your skin redden and blister. One client employee told me recently he thought he had gotten into poison ivy – but it was parsip. He ended up with rashes and blisters, needing medical treatment.
Mn/DOT has a brochure on wild parsnip, including pictures of the plant in different seasons, at http://www.dot.state.mn.us/adopt/files/WildParsnip%20IIII_1.pdf

