Hogweeds and Cowparsnips in Vermont
Members of genus Heracleum are commonly called hogweeds or cowparsnips. We have three species in Vermont:
- Common Cowparsnip (Heracleum maximum)
- European Cow-Parsnip (Heracleum sphondylium)
- Giant Hogweed (Heracleum mantegazzianum)
Only Heracleum maximum is native to Vermont, the other two species are introduced. In particular, Heracleum mantegazzianum, which is highly invasive, has been positively identified at a number of sites, including the following:
- Along the Mallory Brook Trail in East Montpelier (observations)
- Along Lake Ninevah Road in Mt Holly (observations)
- Along Sodom Pond Road in Adamant (observation)
On the other hand, little is known about Heracleum sphondylium in Vermont. New Flora of Vermont [2015] says the species is found along "Roadsides and old fields: occasional (locally common in northeastern Essex Co.). Specimens seen from Essex, Orleans, and Franklin counties." As of July 2023, there are few (if any) positively identified observations of this species in Vermont.
Comments
All three species listed above can cause phytophotodermatitis in humans. There's a lot of misinformation and misunderstanding regarding this potentially serious skin condition. The phototoxic substance responsible for phytophotodermatitis is in the plant sap. Contact with the sap followed by exposure to UV light (e.g., sunlight) are both required for a positive reaction.
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