To the budding field biologist--
Lately, giant hogweed (
Heracleum mantegazzianum) inquiries are frequent. Visitors have asked our Natural Resources staff and Outdoor Experiences staff if the plant species is present in northeast Ohio. Specifically, folks are concerned about the skin irritation that giant hogweed can cause. This plant is an introduced/nonnative species to Canada and the Lower 48. From time to time, it does turn up in Ohio. One such rare occurrence is at a household residence in Pepper Pike, Cuyahoga County. Its North American distribution is typically of more northern latitudes than Cleveland. For example, I've seen and confirmed giant hogweed growing roadside in Vermont and Ontario. What visitors of Cleveland Metroparks are stumbling upon is a look-alike, cow parsnip (
Heracleum maximum). This flowering plant is native to Ohio. But not so fast; hands off. Better safe than sorry!
Let’s dig deeper.
A) To distinguish giant hogweed from cow parsnip, you can look at the overall height and the leaf morphology (shape). Giant hogweed, in its matured state will be taller than you, even if you’re 6-ft tall like me. When visitors submit photos for identification purposes, the camera angle is the first thing to give it away. The shot is typically aimed down from a high profile to capture the image of the lower-growing cow parsnip. Also, a trained eye can look at the leaf sinuses. For example, if you are to look at a webbed duck foot and compare it to your own hand, the space between your fingers are very deeply lobed when compared to the shallow "sinuses" of the webbed duck toes. Giant hogweed has very deep leaf sinuses, like your hand. In addition, giant hogweed leaves are more toothed than cow parsnip, meaning the edges (leaf margins) are highly serrated.
B) Visitors often mention the word poisonous in relation to giant hogweed. In this case it's more appropriate to say, toxic, because it is considered a phototoxic plant. This means that if you are to end up with the sap on your skin while the sun is shining, you would undoubtedly end up with inflamed and irritated skin. From what I've been told, the dermatitis is very bad and may last for multiple years. I’ve never had the pleasure contending with this beast of a plant, just poison ivy, stinging nettle, and the like. Cow parsnip, being so closely related to giant hogweed, may also contain a toxic compound or skin irritant. The dermatitis is not severe like that from the big bad giant hogweed. Enjoying through the lens of your eye or camera is still the safest route, regardless of your skills in identification.
If you're interested in further reading, look up water hemlock (
Cicuta maculata) and Queen Anne's lace (
Daucus carota) through the Plants Database via USDA Natural Resource Conservation Service: [
plants.usda.gov]. These plant species are in the same family as the hogweed and parsnip, the Carrot Family (Apiaceae).
-Marty Calabrese, Naturalist