Giant Hogweed
( Heracleum mantegazzianum )
Giant hogweed is a hardy perennial plant. Native to Asia, it was introduced to North America likely as an ornamental garden plant.
What is Giant Hogweed?
Hogweed can grow as high as 6 meters having a dark reddish stem that can grow 5-10 cm in diameter. Leaf stalks are spotted and produce a compound leaf that can expand to 1.5 meters across. Each leaflet is deeply grooved or divided. Both stems and stalks are hollow and produce course hairs around a blister like area on the plant. In summer small white flowers form into a large umbrella-shaped head which can reach up to 1 meter in diameter.
Where is Giant Hogweed found?
It can be found throughout southern Ontario. Isolated plants have even been reported as far north as Haliburton County. Hogweed can grow in a wide variety of habitats, however it is most often found along roadsides, streams and riverbanks.
How does Giant Hogweed Affect you?
The blister like areas on stems and stalks leak a clear watery sap containing furocoumarins (psoralens), which sensitize skin to ultraviolet radiation (sunlight). Exposure to sunlight can cause severe burns that usually result in blistering and painful dermatitis. Inflamed linear lesions on the skin can sometimes appear where the person has brushed against the plant. Blisters occurring from contact with hogweed sap can develop into purplish or blackened scars sometimes up to 48 hours after exposure. Contact can lead to recurring dermatitis. Contact with the eyes can lead to temporary or possibly permanent blindness.
If you become exposed
- Wash the affected areas immediately with soap and water if available
- Keep affected areas out of direct sunlight
- Seek medical advice as soon as possible
What you can do to help
