The U.S. Department of Agriculture and Departments of Natural Resources of multiple states have issued warnings against Heracleum mantegazzianum, known as the giant hogweed.
The plant, which has huge leaves, hairy stems and "towering, umbrella-shaped white flowers" that bloom in late spring and can grow up to five meters tall. It is a relative of carrots and parsnips, but the resemblance is small: the giant hogweed's sap is released when touched, and the toxic substance can make skin hypersensitive to the sun.
The sap can cause phytophotodermatitis, which can lead to blisters, scarring and discoloration, and leave skin sensitive to the sun for years. And "sap in the eyes can cause temporary or possibly permanent blindess," the U.S. Forest Service warns.
The problem, officials say, is that the plant has a lot of look alikes, including a similar but less harmful plant called cow parsnip and Queen Anne's Lace, that can make it very difficult to effectively eradicate.