Giant Hogweed

Beware of Giant Hogweed

Imagine breaking out with severe, blistery rashes—much worse than those caused by poison ivy—after a combination of exposure to a certain weed’s sap and the sun.

This reaction, known as phytophotodermatitis, can be caused by an invasive weed called giant hogweed (Heracleum mantegazzianum). It is a short-lived herbaceous perennial that can grow up to 15 feet tall, producing gigantic, showy, umbel-shaped flowers resembling that of wild carrot, only much larger.

Giant hogweed is native to the Caucasus region in Europe and Central Asia. It was introduced to North America as an ornamental, but has escaped cultivation and invaded natural areas. It has been documented in the neighboring states of Pennsylvania, Maryland and most recently, Virginia—which is considered to be intentionally planted. The plants reproduce both vegetatively, through perennating buds on the crown tissue and root stocks, and by seeds. Despite its vicious sap, it is not toxic to livestock.

Giant hogweed is often confused with the native plant, cow parsnip (Heracleum maximum), which has been reported in several parts of the state. Cow parsnip also contains the chemical, furocoumarins, that is capable of causing rashes upon contact with the sap, but the rashes are not nearly as severe as those caused by its cousin.

Giant Hogweed Identification

The leaves of giant hogweed are more deeply lobed than cow parsnip, resembling fingers of a palm with pointed tips on leaf margins, as opposed to palm-shaped leaves with shallow lobes and blunt serrations. The hairs of cow parsnip are fine and downy, compared to the short stiff hairs of giant hogweed. Other plants that are commonly mistaken for giant hogweed include wild parsnip, angelica, elderberry, poison hemlock and giant ragweed, on occasion.

Managing Giant Hogweed

If you see a plant that fits this description, notify your local WVU Extension office for proper identification, documentation and possible eradication. But most importantly, don’t touch it!

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