Giant hogweed was introduced to the United States from Asia in 1917 as an ornamental plant. Pretty as it may be, it is more dangerous than poison ivy and can cause blindness if its sap finds its way into your eyes. It has recently been spotted growing along a road in Calhoun County, southwest Michigan. The county health department has warned people to "be cautious."
Atlas Obscura has more:
Uncommon in the United States, giant hogweed is "a public health hazard that ranks up there higher than poison ivy, poison oak and poison sumac," according to Michigan's Department of Agriculture and Rural Development. A member of the Federal Noxious Weeds list, giant hogweed produces a toxic sap that can cause severe skin irritation—including blistering that leads to permanent scarring—and even blindness if the sap comes into contact with your eyes.
(Image: Rüdiger Wölk/Creative Commons)