Dangerous Hogweed Plant That Causes Blindness Found In Northern U.S.

The dangerous hogweed plant was found in Calhoun County, Michigan. The giant weed can reportedly cause permanent blindness and blistering and scarring of the skin. The sap on the hogweed plant’s roots, leaves, stem hairs, seeds, and flower heads can cause the medical conditions.

Pennfield Township workers have now removed the hogweed plant from where it was found near Battle Creek. The weed can grow up to 18 feet tall and has a green stem with bristles, purple or dark red spots, and a white flower. The invasive weed began spreading across New York recently, according to warnings issued by the state’s Department of Environmental Conservation.

The hogweed plant (Heracleum mantegazzianum) is a member of the carrot family. The weed is not native to the Great Lakes area. It is believed that the dangerous plant was introduced to the region from Central Asia during the 1900s — it was used to display in gardens and arboretums. Michigan agricultural officials launched a “search-and-destroy” plan against the noxious weed in 1998.

“Giant Hogweed is a public health hazard that ranks up there higher than poison ivy, poison oak and poison sumac in respect to its potential to harm humans,” a notice on the Michigan Department of Agriculture & Rural Development website warns.

Hogweed is also listed on the federal noxious weed list, meaning it is illegal to sell or transport the dangerous plant across state lines.


“The plant can be difficult for the outdoor enthusiast to identify,” according to the Michigan State University Extension website. The publication also noted that “with very limited distribution in Michigan, a vigorous tramp through the woods or wetlands is not likely to expose anyone to hogweed.”

“Hogweed sap, which contains photosensitizing furanocoumarins, contacts human skin in conjunction with sunlight, it can cause phytophotodermatitis — a serious skin inflammation,” according to the New York State Department of Environmental Conservation. “In brief, the sap prevents your skin from protecting itself from sunlight, which leads to a very bad sunburn. Heat and moisture (sweat or dew) can worsen the skin reaction.”

The phototoxic blistering reaction on the skin can reportedly begin about 15 minutes after coming into contact with the dangerous hogweed plant. The sensitivity typically peaks between about 30 minutes and two hours after contact with the noxious weed has occurred. Painful blisters begin darkening after five hours, and can remain visible for up to five months. Sensitivity to sunlight while the blisters are present is reportedly common, as is short-term scarring.

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