Wild parsnip is a non-native invasive plant that blooms bright yellow in late June through mid-August. In early July this three to five foot plant is often seen in overwhelming numbers along highways and county roads. Right now in late July, the central stalks are turning brown and the bright yellow dill like flowers are beginning turn a dull yellow-brown as seeds begin to form.

Wild parsnip is a non-native invasive weed that has recently begun taking over ditches and roadways in our area.  Besides out-competing native and other desirable plants, wild parsnip is harmful to people. Its sap, activated by sunlight, can cause a severe scarring sunburn on skin that has come in contact with the plant. 

The burn causing chemical is in all parts of the plant: leaves, stems and flowers.

This biennial plant is easily seen in mid-summer when the 3- to 5-foot tall flat topped dill-like yellow flowers are visible.

You can easily avoid the burns with some common sense practices: 

• Make sure your bare skin is fully covered when in contact with the plant. That means long pants, long sleeves, and waterproof gloves. I have safely removed thousands of wild parsnip plants without a single burn. 
• Do not weed whip wild parsnip. Weed whipping slices and dices plants into little pieces that spray not just on the ground, but on you. Any piece that lands on your bare skin or soaks through your clothing will cause burns if sunlight hits it.
• Use a riding mower (not a push mower) to mow wild parsnip so mowed pieces are left on the ground and not on you. If possible, begin mowing in late May and continue through the summer, at a height of 8 inches or less. Mow the area for about three years and the parsnip will be virtually gone.
• Use a Parsnip Predator tool, available online through Prairie Enthusiasts, to easily and safely remove wild parsnip as whole plants. The Predator quickly severs the parsnip tap root and the plant can be pulled from the ground like a knife through butter. 

Wild parsnip can easily be controlled and virtually eliminated within 3-5 years through proper mowing or safe physical removal practices.

Photos/illustrations by Margaret Smith

We need to save (and even encourage expansion) of the native plants along the roadsides — those are very important habitat that is disappearing. They are at risk not only from wild parsnip, but from the blanket spray treatment of wild parsnip that kills all herbaceous plants/forbs/non grass plants that are in the roadside along with the wild parsnip.

Mowing at the right time for 3- 5 years is 90%-100% effective in getting rid of wild parsnip. If you can’t mow throughout the summer, then mow after the flower heads have formed (late June) but before seeds enlarge (about mid to late July, about 2 weeks after flowering). Mowing after seeds have developed actually spreads the seeds that are caught in mower blades. Mowed plants may re-sprout and produce flowers, but rarely are those seeds viable.

Physical removal over a 3-5 year time frame with a spade or Parsnip Predator is 90-100% effective if done correctly. Cut the tap root 1-2 inches below the soil surface with a sharp shovel, spade or easiest of all, the Parsnip Predator.

If the flowering plants are not removed by mowing or physical removal, each plant can set hundreds of seeds within a 10 foot area of the mother plant.  

Once the plant flowers and sets seed, it dies. Keeping new plants from growing or setting seeds for 3-5 years virtually eliminates wild parsnip in an area and allow the native and other desirable plants to flourish to the benefit of both wildlife and humans.

More information

• Controlling biennial invasives without herbicide using a Parsnip Predator – The Prairie Enthusiasts
• Known wild parsnip infestations in the upper Midwest- Great Lakes Early Detection Network

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About the author

Margaret Smith was recently one of only four people across Wisconsin in 2020 to receive an “Invader Crusader” award from the Wisconsin Invasive Species Council, which honors Wisconsin citizens and organizations for their significant contribution to prevent, control or eradicate invasive species that harm Wisconsin’s lands, waters and wetlands.

“Over the past three years, Margaret has worked tirelessly in Pierce and St. Croix Counties on efforts to control invasive and dangerous wild parsnip,” the council says.

Smith spearheaded an effort to collect information on the prevalence of wild parsnip along the roadways of Kinnickinnic township and organized a group of Master Gardeners and other volunteers who used a GPS mapping tool to identify the areas of low or high populations of wild parsnip. This allowed the township to use the best control method for the area, saving money on unneeded pesticide and protecting local wildflowers and pollinators. Margaret also coordinated educational efforts including a class on identification and control for local property owners.

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