GIANT HOG WEED

Giant Hogweed, Heracleum mantegazzianum

Human Health Issues

Giant hogweed can be a serious health hazard for humans. Its watery, clear sap contains photosensitizing compounds (furanocoumarins), which, when in contact with human skin and in combination with UV radiation, can cause burning. Content varies depending on plant part, but contact should be avoided at all times. The reaction of the skin depends on individual sensitivity. After 24hrs, reddening and swelling of the skin can be noticed, which is followed by an inflammatory reaction after 3 days. Depending on individual sensitivity, effects can last for months and skin can remain sensitive to UV light for years. Research has also shown that furanocoumarins in general may be carcinogenic and teratogenic.

Often Mistaken For

Giant hogweed has been mistaken for other species, especially others in the carrot family. These species include; Angelica, Wild carrot (daucus carota), Goutweed (aegopodium podagraria), poison hemlock (conium maculatum), water-parsnip (sium suave), spotted water-hemlock (cicuta maculata) and angelica (angelica atropurpurea). Once again, its "giant" size is the easiest distinguishing feature, as it towers above these other species.

Description

Plants forming rosettes to 1m high the first year; in the second year, either sending up a flowering stem, or remaining vegetative and producing a very large rosette of huge leaves, these including their petioles, up to 2m high, and flowering in the third year.

Distribution Map

If you know of a sighting and wish to report it, the Ontario Ministry of Natural Resources is maping Giant Hogweed populations.
Go to: Click here

Giant hogweed invades Russia Click here

Giant Hogweed Video Click here

Media Items

Figure 1: Second year giant hogweed plant with rosette leaves up to 125 cm high plus central stem with 2 leaves emerging through the top of the rosette. Central stem produces large umbel of flowers. Top


Figure 2: Young giant hogweed plant. Top


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Figure 4: Cross-section of giant hogweed stem. Top


Figure 5: Stem of giant hogweed exuding clear, watery sap. Top


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Figure 7: Leaves of giant hogweed. Top


Figure 8: Underside of giant hogweed leaf. Top


Figure 9: Giant hogweed on field edge. Top


Figure 10: Giant hogweed in field. Top


Figure 11: Umbel of giant hogweed flowers. Top


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Figure 12: The Biology of Invasive Alien Plants in Canada
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Figure 13: Education poster for the general public
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Figure 14: Educational poster for outdoor workers.
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