Date: May 22, 2019

Partly cloudy. 30 percent chance of showers early this evening. Fog patches developing late this evening. Wind southeast 30 km/h gusting to 50 becoming light this evening. Low 12.


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Giant Hogweed

(Heracleum Mantegazzianum)

This page was reviewed or revised on Monday, June 26, 2017 3:55 PM

What is giant hogweed?

Giant hogweed is a hardy perennial plant that comes from Asia and was introduced to North America as an ornamental garden plant.

 The plant can grow 4.5 - 6.0 metres (15-20 feet) tall. Its stem is hollow with dark reddish-purple splotches and coarse white hair. The leaves can grow up to 1.5 metres (5 feet) wide and have hairs on the underside. It produces flat, oval shaped fruit and in the summer, small white flowers.


Photo credit: City of Coquitlam                      

How can it affect my health?

A clear, watery sap found in the stem and plant hairs can cause a reaction that makes the skin sensitive to sunlight.

Photo courtesy of USDA APHIS PPQ Archive, USDA APHIS PPQ,

Reactions can happen up to 48 hours after contact. You can get painful blisters and burns. Blisters can lead to purple and black scars that may last for long periods. Contact with the eyes can cause temporary and sometimes permanent blindness.

What should I do if I contact hogweed?

• Wash affected areas immediately
• Keep the affected area out of the sun
• Seek medical advice

What should I do if I find a giant hogweed?

Because of the possible health effects caused by the Giant Hogweed, remove it from your property as soon as possible. When removing it, avoid getting sap on your skin. Wear protective clothing, including gloves, long sleeves, pants, and eye protection.

For instructions to remove this plant contact:

  • County of Lambton
    Building Services:
  • City of Sarnia
    Community Services:
    519-332-0330 ext. 213

For more information contact:

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