Surveyers Find Phototoxic Plants Along the Paint Creek Trail

Oakland Township Stewardship technicians surveying the from Dutton Road to Gunn Road Tuesday for the invasive, highly toxic giant hogweed found multiple populations of the native look-alike species cow parsnip, also a toxic plant.

The technicians did declare the area free of giant hogweed, according to a press release from Midwest Invasive Plant Network, though a staff member from the Michigan Department of Agriculture & Rural Development is still investigating the scene.

“I had heard maybe two days ago that somebody had found giant hogweed at that site," said Mike Phillip of the Michigan Department of Agriculture & Rural Development.

“At this point, from our perspective, we can’t say if it’s parsnip or hogweed.”

“The cow parsnip is not as toxic as the giant hogweed," though it is still a toxic plant, said Michele Arquette-Palermo, education and stewardship director of the Clinton River Watershed Council. She added that the stewardship technicians routinely drive the trails in the summer looking for "invasive plants and bad weeds, then (they) pull them out."

Like giant hogweed, the sap of cow parsnip also contains a phototoxin that reacts with ultraviolet light to cause skin irritation ranging from a mild rash to severe blistering, according to the New York State Department of Transportation. It lists cow parsnip as a dangerous plant.

“Just don’t touch it," Phillip said. "It’s the sap that is dangerous."

For the skin reaction – called phytophotodermatitis – to occur, the skin contaminated with plant sap must be moist (usually perspiration) and then exposed to sunlight, according to the Michigan Department of Agriculture.

The MDA says cow parsnip can reach a height of 5-8 feet in Michigan. It has other characteristics:

"Unlike Giant Hogweed, the stem maybe entirely green or have a slight purplish cast, is deeply ridged and only up to 1-2 inches in diameter. Hairs on cow parsnip are fine, soft and fuzzy, rather than coarse like those on giant hogweed. Although present on both leaf surfaces, the soft hairs occur primarily on the lower surface and give the leaves a velvety appearance. Mature leaves measure up to 2 to 2 ½' in diameter. Cow parsnip generally flowers from early June through early July in Michigan, typically several weeks before Giant Hogweed, and produces much smaller, flat-topped flower clusters."

In a 1965 document on cow parsnip by Oregon State University Extension Vegetable Production Specialist Andrew Duncan, he notes that some farmers do not like to grow and handle cow parsnip because of its toxic effect on the skin, particularly from flowering time through maturity.

"When working with parsnip after it has flowered," Duncan advised, "wear gloves and protective clothing."

Phillip said he doubted the plant found along the Paint Creek Trail is actually giant hogweed, though he can't say for sure until the staff member investigates the site.

"19 out of 20 reports for giant hogweed that we get are usually cow parsnip or similar plants," he said. "It's probably parsnip."

For more information about giant hogweed, cow parsnip and other invasive plants, visit the Midwest Invasive Plant Network website.

If you spot giant hogweed, which is highly invasive and listed as a Federal Noxious Weed, call the Michigan Department of Agriculcure & Rural Development at 517-373-1087 or the U.S. Department of Agriculture at 734-942-9005.