Giant Hogweed (Heracleum mantegazzianum)

By Nicole Gibson

The invasive species Giant Hogweed has taken root in Collingwood and the surrounding area. Native to Asia, this ornamental plant has likely escaped from gardens and is spreading through wild and “waste” places (like ditches and vacant fields) in our watershed. This plant is of particular interest to gardeners and outdoorsy folks as it can pose a serious health risk.

Giant Hogweed resembles some of our native species, such as Angelica, Queen Anne’s Lace and Cow parsnip. However, it can grow up to five metres tall and has an herbaceous stem five to 10 centimetres in diameter. The stem and leaf stalks are covered with coarse hairs, and are often purple-spotted. Hogweed also produces a white umbrella-shaped flower from June to July which will create large, flat, oval seeds.

When the leaves, stems, or bristles are broken they secrete a clear sap which can cause painful blistering and dermatitis where the sap has come into contact with skin. Permanent blindness can result if the sap comes in contact with eyes. Generally, reactions occur within 48 hours after exposure. If you believe you have come in contact with Giant Hogweed sap, cover up the affected areas and keep them out of direct sunlight. Wash the affected areas immediately with soap and cold water, and seek medical attention as soon as possible.

The Nottawasaga Valley Conservation Authority is testing an experimental control method, spraying a mixture of soap, salt, and vinegar on Hogweed in a public space in Collingwood. This method is a possible alternative to applying herbicides considering the plants’ close proximity to water. To date the results have been positive, with leaves wilting and burning, but more time is required to determine the experiments effectiveness.

For more information on Giant Hogweed, please visit www.nvca.on.ca and refer to the NVCA’s fact sheet. For help identifying Giant Hogweed or to report a sighting, contact Nicole Gibson at the NVCA at (705) 424-1479, ext. 261 or ngibson@nvca.on.ca. Be prepared to send detailed photos. Giant Hogweed may also be reported to the Ontario Federation of Anglers and Hunters Invading Species Awareness Program through the website www.invadingspecies.com or their hotline: 1-800-563-7711.

 

--Last edited by tracer on 2009-09-08 20:35:44 --

Thanks Tracer, some very good info. I have had to eliminate 2 on my place I placed a large plastic leaf bag over top then ripped out by the roots wear goggles long sleaves and gloves, after pulling burn it.

Sounds like real bad stuff.  Glad we don't have it here yet.