Wild parsnip (Pastinaca sativa) is a member of the carrot family with origins in Europe and Asia. It’s not known how it came to this country—if it was brought over as a possible food source by immigrants or if a seed was transported accidentally. The first records of this aggressive plant in Wisconsin date back to 1894.
An Invasive Species
Wild parsnip is found throughout Wisconsin in sunny areas along roadsides, bike trails, fence rows, abandoned fields, and prairies. The plant is an invasive species that will spread quickly providing a threat to native plants.
Besides being invasive, wild parsnip has serious health hazards when it comes in contact with human skin. If exposed skin comes in contact with the sap from any part of the plant in the presence of sunlight, the sap will cause a severe burn with blistering, typically 24 to 48 hours after exposure; this reaction is referred to as phytophotodermatitis. Don’t mistake the burn of wild parsnip for the itchy rash of poison ivy.
About Wild Parsley
During July, wild parsnip is one of the dominant yellow-flowered weeds along the roadsides. When flowering, the plant will be between 3 to 6 feet tall. The stem is thick, hairy, grooved, and hollow with leaves arranged alternately on the stem. There are hundreds of tiny yellow flowers with five petals, in flat-topped umbrella like clusters called umbels at the tops of the stems and branches. Besides the hundreds of flowers, one plant will also produce hundreds of flat, oval, ¼ inch seeds. The seeds are dispersed in September and can remain viable in the soil for four years. Wild parsnip seedlings are among the first plants to green up early in the spring. The first year or so, wild parsnips will be a rosette about 6 inches tall. When conditions are right, a flower stalk is sent up; blooms, and then the plant will die
How to Control
There are a few different ways to control wild parsnip. If detected early, the taproot of each plant can be cut with a spade just below ground level, for a larger patch a power brush-cutter could be used. Mowing should be done before seed formation with follow up mowing throughout the summer. Burning is not very effective for controlling wild parsnip; plants will just re-sprout. Herbicides such as those containing glyphosate are effective with the right timing of treatment. Always wear gloves, long pants, and long sleeves when working with wild parsnip. When using a brush-cutter, it’s also advisable to add a face shield.
Wild parsnip can be confused with the endangered native prairie parsley (Polytaenia nuttallii). The websites for the Wisconsin DNR (http://dnr.wi.gov), UW-Extension (http://hort.uwex.edu/), and Invasive Plant Association of Wisconsin (http://ipaw.org/) provide photos and detailed descriptions of wild parsnip for accurate identification of this annoying plant.
Certified Master Gardener