Originally from Asia, giant hogweed has been introduced into Europe, Great Britain, Canada, and the United States. Although it is listed as a Federal noxious weed and is illegal to bring into the United States or move across State lines, giant hogweed is known to occur in New York, Ohio, Pennsylvania, and Washington. Reports of infestations have been received from Maine, Michigan, and Washington, DC.
This weed has been planted as an ornamental in the United States and may have also been brought into this country for its fruit, used as a spice (golmar) in Iranian cooking.
As its name indicates it can grow to 15' — 20' high. Except for size, it closely resembles cow parsnip, Heracleum lanatum, a plant native to Washington.
It is further distinguished by a stout dark, reddish-purple stem and spotted leaf stalks. The stem and stalks are hollow, stems vary from 2" — 4" in diameter. The compound leaves of giant hogweed may quickly grow to 5' wide. Each leaflet is deeply incised.
Giant hogweed is a perennial with tuberous root stalks which form perennating buds each year and produces large elliptic dry fruits marked with brown swollen resin canals up to 1 mm in diameter.
Hogweed's clear, watery sap has toxins that cause photo-dermatitis. Skin contact followed by exposure to sunlight produces painful, burning blisters that may develop into purplish or blackened scars that can can last for several years.
Read more: InvasiveSpecies.org