Giant Hogweed


Hogweed (Heracleum sphondylium) is a large perennial plant that grows in wet shady sites. It has white flowers that are clustered like an umbrella and bloom from spring through summer. The stems are dotted with reddish-purple flecks. The giant hogweed can grow up to 5 meters with leaves spanning 1.5 meters.

Is it toxic?
Contains photosensitive compounds, which are activated by ultraviolet light. These compounds are concentrated in the sap of the stalk, stems and leaves. Contact with skin followed by exposure to sunlight can result in a burning sensation, redness and blisters. Onset of symptoms is usually around 24 hours after exposure. Moist air or high humidity increases the severity of response.

Health Effects:

Skin: The skin must be exposed to the sap from the plant followed by sunlight for a reaction to occur. Approximately 24 hours after this exposure, the area becomes red with a burning sensation and small blisters. Blisters may increase in size over the next 2-3 days. The area gradually heals but an area of hyperpigmentation or darkening of the skin may persist for weeks or months.

What to do:
Skin: Remove any clothing that has come in contact with the plant. Wash skin thoroughly with soap and water. Avoid exposure to sunlight for at least 48 hours. If blisters develop or you have any questions or concerns, contact the Poison Control Centre.

How can I prevent exposure?
Wear water-resistant gloves and clothing, and goggles when handling the plant. Do not get any sap on exposed skin.

Need more information: Contact the Poison Control Centre. See also Invasive Species Council of British Columbia for links to additional resources and WorkSafeBC for downloadable pdf document.

Report sightings of invasive species of plants in BC using the Report-a-Weed app.


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