Giant Hogweed Information

Invasive 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

Applied Vegetation Dynamics Laboratory - UK site
Background on the plant and its impacts in Great Britain

Connecticut Invasive Plant Working Group
Facts and control information about giant hogweed

Federal Noxious Weed Inspection Guide
General information including natural history

Invasive Species of Concern in Maryland
Brief page with general information
Page with additional links for giant hogweed

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

Massachusetts Department of Agricultural Resources
Pest alert of giant hogweed

Nanaimo, British Columbia
Canadian site with biological and control information

The Noxious Weed Coloring Book-Giant Hogweed
A coloring book picture of giant hogweed

Oregon Department of Agriculture
Background and images of giant hogweed

Pennsylvania Bureau of Plant Industry
About giant hogweed in Pennsylvania

University of New Hampshire - Cooperative Extension site
Information about this plant in New Hampshire

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

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

USDA Plants Database
Map of distribution, links and other information

Washington Department of Ecology
General information and photographs

Washington State Noxious Weed Control Board
Page with pictures, ecological and control information