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University of Minnesota Extension

Please Don’t Touch the Plants

I spent Saturday working outside, only to find red spots all over my legs at the end of the day. There are many plants in Minnesota that can cause skin irritation and it seems I got into one of them. In the interest of saving you from the same fate, let me introduce you to several of these to avoid this summer.

Wild Parsnip (Patinaca sativa.) is a toxic plant with an edible root that has invaded many of the roadsides in Douglas County. The flowers are yellow and arranged in an umbrella shape, the leaves are coarse with saw–toothed edges, and the stem is somewhat hairy.  Wild Parsnip grows two to five feet tall and is similar the ornamental Queen Anne's Lace. Leaves are course, with saw-toothed edges. Several herbicides exist that provide adequate control of wild parsnip. However, repeated applications may be needed for control.

Giant Hogweed (Heracleum mantegazzianum) is a biennial or perennial herb in the carrot family that grows 15 to 20 feet tall with stout, bristly, dark reddish-purple stems and spotted leaf stalks. The white, umbrella shaped flowers can be as large as 2-2.5 feet in diameter. Giant Hogweed is on the Minnesota Department of Agriculture early detection list. It is not yet present in Minnesota but is making its way here via Wisconsin. 

Cow Parsnip (Heracleum Maximum) is a large-leafed plant that can reach heights of more than seven feet and also has white umbrella shaped flowers. Cow Parsnip is present throughout Minnesota, often seen in late spring and early summer along roadsides in wet ditches. Cow Parsnip is the native counterpart to the highly invasive non-native Giant Hogweed.

The stems and leaves of all the above plants contain furocoumarins, a photosensitive chemical that can lead to rash and blisters on some people after exposure to ultraviolet light. 

Stinging Nettle (Urtica dioica) and Wood Nettle (Laportea canadensis) are both native plants that cause minor skin irritation. The stems and leaves of these plants are covered with long, stinging hairs. At the slightest touch, the hairs break off, their sharp points penetrate skin and release sap that inflames the skin. Both nettles grow 2-7 feet tall. Wood Nettle grows in shaded, wooded areas, and Stinging Nettle grows in full sun. 

Poison Ivy (Toxicodendron radicans and T. rydbergii) can be found in many places and have many forms.   It can grow as a shrub or a 12’ vine.  New leaves are often shiny and reddish, older leaves have a dull cast and are green. The old adage “Leaves of three-let it be” is good advice. Roots, leaves and stems contain an oily resin called urushiol which typically causes an irritating rash, blisters, or swelling when exposed to human skin, and occasionally on livestock. Burning poison ivy is very dangerous, as the smoke can contain urushiol and cause serious respiratory or other systemic health problems if inhaled.

For more information about any of these plants, please the Douglas County Extension Office at 320-762-3890.

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