News

Hogweed creeps into northeast Ohio

August 18, 2005

2508

JEFFERSON, Ohio – A weed described as a freak of nature has spread across Pennsylvania and is making its way through Ohio.
The Asian plant, giant hogweed, has a phototoxic sap that can burn your skin when exposed to sunlight, according to David Marrison, Ohio State University Extension educator in Ashtabula County, one of the locations where the weed has been discovered.
Description. Heracleum mantegazzianum, named after the Hercules of ancient mythology, grows 10-15 feet tall, with its compound leaves ranging from 3-5 feet wide.
The robust weed blooms in early July, producing a flower head up to 2.5 feet in diameter.
Its green, hollow stem is 2-4 inches in diameter with dark, reddish-purple blotches.
Hogweed stems do not start out hollow and they don’t bloom until the second to fourth year of development.
It has hairs on the under side of the leaves that are stiff and stubby. The leaf stalks also have short, coarse, white hairs around the junction of the leaves.
Dangerous sap. The sap of the plant causes photo-dermatitis, making skin extremely sensitive to sunlight.
Photo-dermatitis can cause itchiness, redness, swelling and blistering, with symptoms lasting for days, weeks or even months.
The sap can also cause excessive pigmentation, or hyper-pigmentation, triggering painless skin blotches that develop into purplish or brownish scars and can persist for several years.
“Like poison ivy, you have to respect the danger of it,” Marrison said.
The weed poses a greater risk to youngsters because of its huge, intriguing structure.
Children have been known to use the hollow stem as a telescope or sword, exposing the dangerous phototoxic sap, he said.
Also, if animals get the sap on their fur and then your skin comes in contact with the animal, the sap can be transferred.
Identification. It is important to be able to identify the plant since it looks like several other common weeds, Marrison said.
Hogweed can be confused with parsnip, angelica or poison hemlock and also resembles Queen Anne’s lace.
It is possible to walk through it and work around it, as long as you don’t get sap on your skin, he said. The sap isn’t exposed until the plant is punctured.
Federal noxious weed. This member of the carrot or parsley family is listed as a federal noxious weed, making it illegal to propagate, sell or transport.
It has been found in 11 states including: Pennsylvania, Maryland, Connecticut, Washington D.C., Maine, Massachusetts, Michigan, New York, Ohio, Oregon and Washington.
Coming to Ohio. Since the weed has been found in more than 600 sites in Erie County, Pa., it is not surprising it has spread across the border to Ohio.
There are more than 10 confirmed sites in Ashtabula County and a site confirmed in both Lake and Columbiana counties.
There have been reports of the weed through many counties from the northeast corner of Ohio down through Franklin County, but those reports are yet to be confirmed, Marrison said.
It is believed to spread quickly because of its prolific seed and people’s attraction to its massive structure.
When people see how unusual it is, they dig it up and take it home for use in their own gardens, Marrison said.
Disposal. When the weed is found and correctly identified, there is no over-the-counter herbicide that works to successfully kill it, Marrison said. Only restricted-use chemicals can do the job.
It is found in places such as moist road ditches or brush patches that aren’t mowed often.