Giant Hogweed

Giant hogweed (Heracleum/mantegazzianum), an invasive exotic plant, is quickly spreading throughout New York State. Giant hogweed is especially serious because exposure of skin to the plant fluids can cause severe skin reactions in most people. The plant toxins work by altering skin cells' DNA so that the affected skin cannot protect itself from harmful UV radiation. Skin reactions begin with reddish, ringling blotches within a few hours of contact with plant sap along with exposure to ultraviolet light from the sun or other sources. Blisters begin forming within a day or two of exposure and by the third day, broken blisters begin oozing clear to yellowish fluids. Sound serious? That's not the end of it. Even with medical treatment, severe scarring and long-term or permanent purplish skin discolorations and sensitivity to sunlight is likely. The chemical compounds that cause the skin lesions are also known carcinogens.

Unfortunately, this plant is sometimes mistaken for closely related "look-a-likes" including cow parsnip, angelica, and water hemlock. Hogweed's distinctive tri-lobed, compound leaves are 3-5 feet across. Umbrella-shaped white flower heads can be 8 to 24 inches in diameter. Two to four inch think, hairy flower stalks with purple blotches can reach 15 to 20 feet in height in a single growing season. "It's like Queen ann's Lace on growth hormones" say hogweed experts.

Eradication of giant hogweed is the goal. Since New York State does not have a noxious weed law which allows or requires removal of noxious plants by public officials, it is up to individual landowners and municipal workers to deal with he problem. Various counties have recently developed a giant hogweed removal protocol with has been shared with county highway workers and many town highway crews. County highway workers have been told to report areas of hogweed infestation, but they are not supposed to attempt removal of the plants themselves.

Very careful mechanical control is an option, but is challenging. Ideally, hogweed plants should be removed before they flower and spread seeds. All plant parts should be carefully removed, bagged, and sent to a landfill. Herbicides such as glyphostate can be applied, often with repeated applications throughout the season or over a number of years in order to kill off regrowth or new seedlings. Gloves and protective clothing are required. Hogweed control is best left up to professionals who may also use steam sprays or herbicides which can only be applied by licensed applicators.

To report sightings of giant hogweed, call the NYS Agriculture and Markets NYS-HOTLINE at 1 (800) 554-4501 Ext. 2087. Interned users can type "giant hogweed" into their favorite web searching site for a long list of reference sites. some recommended invasive species web pages include: http://plants.usda.gov, http://www.ipcnys.org and http://tncweeds.ucdavis.edu.

Picture Credit: John Whitney, USDA Natural Resources Conservation Service.