Giant Hogweed

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A plant found in Michigan puts Poison Ivy to shame. It's called the Giant Hogweed.

It resembles a supercharged version of Queen Anne's Lace and grows up to 15 feet tall. The plant has a purple tinged stem and sprays of white blossoms a foot or more across.

A toxin in the sap attacks human skin, causing swelling, burns, blisters, and permanent scars. Officials say the Giant Hogweed is the most dangerous plant in the state and to avoid it at all costs.

It's been found in about a dozen states and in Michigan it's been found in Branch, Jackson, Ingham, and Gogebic counties. Extended Web Coverage

Giant Hogweed

History and Impact

  • Giant Hogweed is originally from Asia.
  • It is similar in appearance to our native cow parsnip, only it is much larger and the hairs on the under surface of the leaf are shorter (about .25 mm long).
  • A public health hazard, hogweed's clear, watery sap has toxins that cause photo-dermatitis.
  • Skin contact followed by exposure to sunlight produces painful, burning blisters that may develop into purplish or blackened scars.

Biology and Morphology

  • A member of the parsley family, its most impressive characteristic is its massive size.
  • It reaches a height of 10 to 15 feet when in flower and has hollow stems, 2 to 4 inches in diameter with dark reddish-purple spots and bristles.
  • Coarse white hairs at the base of the leaf stalk are also purplish, and each purple spot surrounds a blister-based hair.
  • The deeply incised compound leaves grow up to 5 feet in width.
  • Giant hogweed flowers mid-May through July, with numerous white flowers clustered in an umbrella-shaped head that is up to 2.5 feet in diameter across its flat top.
  • The plant produces flattened, 3/8-inch long, oval dry fruits that have a broadly rounded base, and broad marginal ridges.
  • Hogweed prefers moist soil and can quickly dominate ravines and stream banks.

Source: (Department of Natural Resources and Parks Web site) contributed to this report.