Do Not Touch This Plant!

Giant hogweed (Heracleum mantegazzianum) is toxic. Its sap can cause severe skin and eye irritation, painful blistering, permanent scarring and blindness.

Sap can be located in all parts of the plant but the following have higher concentrations: the lower part of the hollow stems and petioles; the hollow hairs on the plant; the foliage, stem, flower, or fruit (seed).


The sap contains photosensitizing furanocoumarins which can cause serious skin inflammation. In brief, the sap prevents your skin from protecting itself from sunlight which leads to a very bad sunburn. Heat and moisture can worsen the skin reaction. The phototoxic reaction can begin as soon as 15 minutes after contact, with sensitivity peak between 30 minutes and two hours after contact.

How to Identify

  • It is a biennial or perennial herb in the carrot family (Apiaceae)
  • It can grow to 14 feet or more.
  • Its hollow, ridged stems grow 2-4 inches in diameter and have dark reddish-purple blotches.
  • Its large compound leaves can grow up to 5 feet wide.
  • Its white flower heads can grow up to 2 1/2 feet in diameter.


  • Painful blisters that form within 48 hours and become dark and pigmented Giant Hogweed can be up to 14 feet tall
  • Scars that last up to six years, though typically only last a few months
  • Long-term sensitivity to sunlight is common
  • Blindness may occur if the sap gets into the eye

Safety precautions

  • Do not touch the plant with bare skin,
  • Do not touch your bare skin with sap-covered gloves,
  • Wear long waterproof gloves, long sleeves, pants, boots, and eye protection,
  • If controlling plants with multiple people, keep a good distance from one another as the sap can splash three to four feet,
  • Apply sunblock before beginning to work,
  • Launder clothes that may have contacted plants,
  • Wash equipment with water immediately after use,
  • Limit exposure to sunlight after control OR work around giant hogweed plants after sunset,
  • DO NOT use a “weed-whacker” or brush cutter – sap may splatter as stems are cut,
  • Keep water, soap, and eye wash near the work area in case of exposure.

When exposed

  • Wash the affected area thoroughly with soap and COLD water as soon as possible,
  • Keep exposed area away from sunlight for 48 hours,
  • If a reaction occurs, topical steroids applied early can reduce the severity of the reaction and ease discomfort,
  • If sap goes in your eyes, rinse them with water and wear sunglasses,
  • If a reaction has occurred, the area of the skin may be sensitive to sunlight for a few years,
  • See a physician if you react,
  • Keep the affected skin away from sunlight for 48 hours.

Where is it found?

Giant hogweed is native to the Caucasus Mountain region between the Black and Caspian Seas. It was introduced to Europe in the late nineteenth century and to North America in the early twentieth century as an ornamental garden plant.

Giant hogweed grows wild throughout Canada and the USA along streams, fields, forests, yards, and roadsides. It prefers open areas with abundant light and moist soil, but it can also grow in partially shaded habitats.

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The Giant Hogweed has beautiful flowers yet its sap is very toxic


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