florida Early Detection Network

IPANE Alerts - Giant Hogweed

Downloadable fact sheet

Giant hogweed comparison table - Table with images to compare giant hogweed with similar looking species

Giant hogweed control - Link to CIPWG site

Giant Hogweed (Heracleum mantegazzianum Sommier and Levier) has been found in all six New England states.

Though this plant has not formed extensive stands in New England, in other states, it has been reported in large patches. This plant is a threat due to its ability to cause skin damage. Contact with sap from broken parts of the plant can result in the skin becoming hypersensitive to the sun, resulting in burns.

Giant hogweed is present along roadsides, in vacant lots and along streams and rivers. It prefers rich, moist soil, in semi-shade conditions. This herbaceous plant can reach heights of 15-20ft. (4.3-5.8m). The stem is hollow and usually blotched with purple. The stem can be 2-4in. (4.8-9.6cm) in diameter. The leaves of this plant have a dissected form and can be up to 9.8ft. (3m) in length.

Giant hogweed flowers from June-July. The inflorescence has many white florets that form a flat-topped umbel. Each inflorescence can have a diameter of up to 2.5ft. (0.72m). The fruits are dry and elliptic, being 0.3-0.4in. (8-11mm) in length and 0.25-0.3in. (6-8mm) in width. The fruits have brown resin canals that can be up to 0.04in.(1mm) in diameter. Giant hogweed is commonly misidentified with other similar looking species. For assistance in identification of giant hogweed, there is a comparison chart which compares images of giant hogweed with that of other similar species.

For information on the control of giant hogweed, see the information below from the website of the Connecticut Invasive Plant Working Group (CIPWG).

Additional Giant Hogweed Links

Connecticut Invasive Plant Working Group - List of Resources on Giant Hogweed

Federal Noxious Weed Inspection Guide - General information including natural history

Invasive Species of Concern in Maryland - Brief page with general information

Invasivespecies.gov - Invasive Plant Alert

Lyrics to the Genesis song "The Return of the Giant Hogweed" - Just for fun-lyrics from a real song

Nanaimo, British Columbia - Canadian site with biological and control information

Washington State Noxious Weed Control Board

Oregon Department of Agriculture - Background and images of giant hogweed

Pennsylvania Department of Agriculture - About Giant Hogweed in Pennsylvania

USDA Animal and Plant Health Inspection Service (APHIS) - Giant Hogweed Activity Sheet

USDA Animal and Plant Health Inspection Service (APHIS) Poster on giant hogweed

USDA, ARS, National Genetic Resources Program - General and taxonomic information

USDA Plants Database - Map of distribution, links and other information