This plant is among the nastiest of all, but luckily it remains relatively rare in Illinois, according to the University of Illinois Extension. Giant hogweed is native to Asia and an invasive species here in the United States, likely introduced because of its use as a spice. So far, it has only been identified in a few Illinois counties, but its range continues to expand.
Giant hogweed is, indeed, giant, regularly reaching heights of 10 feet to 15 feet tall and 5 feet wide, according to the U.S. Fish and Wildlife Service. It has thick, hollow stems that can be 2 inches to 4 inches thick. The stems have vertical ridges, and they often have brownish or purplish spots on them. It produces small, white clusters of flowers that typically bloom between May and July.
Contact with sap from giant hogweed in the presence of sunlight can cause severe skin and eye irritation, leading to blistering rashes, permanent scars and blindness. It’s best to avoid handling this plant, the University of Illinois Extension advises. If you must handle it, always wear protective clothing and gloves to ensure your skin does not make direct contact with the plant and its sap.
Spotted water hemlock