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Heracleum mantegazzianum
Herkulesstaude fg01.jpg
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Asterids
Order: Apiales
Family: Apiaceae
Genus: Heracleum
Species: H. mantegazzianum
Binomial name
Heracleum mantegazzianum
Sommier & Levier

Heracleum mantegazzianum, commonly known as giant hogweed,[1][2][3] cartwheel-flower,[1][2][3] giant cow parsnip,[4][5] hogsbane or giant cow parsley,[6] is a flowering plant in the family Apiaceae. In New Zealand, it is also sometimes called wild parsnip or wild rhubarb.[2] It typically grows to heights of 2 to 5.5 m (6 ft 7 in to 18 ft 1 in).[7] Superficially, it resembles common hogweed (Heracleum sphondylium), Heracleum sosnowskyi, or garden angelica (Angelica archangelica). It is phototoxic and considered to be a noxious weed in many jurisdictions. Giant hogweed is native to the Caucasus region and Central Asia. It was introduced to Britain as an ornamental plant in the 19th century, and it has also spread to many other parts of Europe, the United States, and Canada.

The sap of giant hogweed causes phytophotodermatitis in humans, resulting in blisters and scars. These serious reactions are due to the furocoumarin derivatives in the leaves, roots, stems, flowers, and seeds of the plant.



Green, red-spotted stem with white hairs

Giant hogweed has a stout, bright green stem that is frequently spotted with dark red and hollow red-spotted leaf stalks that produce sturdy bristles. The stems grow to more than 2 m high.[8] The hollow stems vary from 3–8 cm (1.2–3.1 in) in diameter, occasionally up to 10 cm (3.9 in). Each dark red spot on the stem surrounds a hair, and large, coarse white hairs occur at the base of the leaf stalk.

The plant has deeply incised compound leaves which grow up to 1–1.7 m (3 ft 3 in–5 ft 7 in) in width.

Giant hogweed is a biennial or monocarpic perennial,[7]:827 the plants usually begin dying after they have set seed. It usually flowers in its second year from late spring to midsummer, with numerous white flowers clustered in an umbrella-shaped head that is up to 80 cm (31 in) in diameter across its flat top.

The plant produces 1,500 to 100,000 flattened, 1-centimetre (0.39 in)-long, oval, dry seeds that have a broadly rounded base and broad marginal ridges. Tall dead stems may mark its locations during winter.

Introduction to Europe and North AmericaEdit

Distribution of giant hogweed in Europe (2005)

Giant hogweed was among many foreign plants introduced to Britain in the 19th century as ornamental plants. It is now widespread throughout the British Isles, especially along riverbanks. By forming dense stands, they can displace native plants and reduce wildlife habitats.[9] It has spread in the northeastern and northwestern United States, and southern Canada and is an invasive species in Germany, France, and Belgium, overtaking the local native species, Heracleum sphondylium.[9] Giant hogweed was introduced to the Baltics during the Soviet era as fodder for cattle.[10]

In Canada, the plant has been sighted in British Columbia, Alberta, Saskatchewan, Ontario, Quebec, New Brunswick, Nova Scotia, and in isolated areas of Newfoundland. It has been seen in Quebec since the early 1990s.[11] The plant's spread in Ontario began in the southwest and was seen in 2010 in the Greater Toronto Area and Renfrew County near Ottawa.[12]

Giant hogweed was introduced into New York about 1917, and was recorded in British Columbia in the 1930s. It now occurs in the west in British Columbia, Washington, and Oregon and in eastern North America from Newfoundland and Nova Scotia west to Ontario and Wisconsin and south to Indiana, Maryland, and New Jersey.[13][14] It is also recorded occasionally in Michigan,[15] and in June of 2018, it was reported growing in Virginia and North Carolina.[16][17][18] The plant is a federally listed noxious weed in many US states.[13]


Giant hogweed flower head

The sap of the giant hogweed plant is phototoxic; when the contacted skin is exposed to sunlight or to ultraviolet rays, it can cause phytophotodermatitis (severe skin inflammations). Initially, the skin colours red and starts itching. Blisters form as it burns within 48 hours. They form black or purplish scars that can last several years. Hospitalisation may be necessary.[9] Although media reports have suggested that eye exposure to the sap can lead to temporary or permanent blindness, the risk of permanent blindness is not supported by existing research.[19]

These reactions are caused by the presence of linear derivatives of furanocoumarin in its leaves, roots, stems, flowers, and seeds. These chemicals can get into the nucleus of the epithelial cells, forming a bond with the DNA, causing the cells to die. The brown colour is caused by the production of melanin triggered by furocoumarins.

Authorities advise that children should be kept away from giant hogweed, that protective clothing, including eye protection, should be worn when handling or digging it, and that if skin is exposed, the affected area should be washed thoroughly with soap and water and the exposed skin protected from the sun for several days.[9]


Because of its phototoxicity and invasive nature, giant hogweed is often actively removed.

The European Union funded the Giant Alien project to combat the plant.[20][21] On August 2, 2017, it added the species to its List of Invasive Alien Species of Union concern,[22] thus placing restrictions on keeping, importing, selling, breeding and growing it and requiring governments to detect and eradicate it throughout the EU.

In the UK, the Wildlife and Countryside Act 1981 makes it an offence to plant or cause giant hogweed to grow in the wild.[9][23]

In the US, hogweed is regulated as a federal noxious weed by the US government, and is illegal to import into the United States or move interstate without a permit from the Department of Agriculture.[24] The USDA Forest Service states pigs and cattle can eat it without apparent harm.[5] The New York State Department of Environmental Conservation has had an active program to control giant hogweed since 2008.[25] In 2011, Maine state horticulturists, describing the plant as "Queen Anne's lace on steroids", reported that it has been found at 21 different locations in Maine, with the number of plants ranging from one to a hundred.[26]

In popular cultureEdit

Progressive rock band Genesis tells the story of the plant's introduction to Britain and its invasive nature in "The Return of the Giant Hogweed", a track on their album Nursery Cryme (1971).

See alsoEdit


  1. ^ a b "Heracleum mantegazzianum". Germplasm Resources Information Network (GRIN). Agricultural Research Service (ARS), United States Department of Agriculture (USDA). Retrieved 2013-08-06. 
  2. ^ a b c "National Pest Plant Accord". Ministry for Primary Industries, Government of New Zealand. 2012. p. 70. Archived from the original on 4 February 2018. 
  3. ^ a b "Species Profile- Giant Hogweed (Heracleum mantegazzianum)". National Invasive Species Information Center, United States National Agricultural Library. 
  4. ^ "Giant Hogweed". the Ontario [Canada] Federation of Anglers & Hunters. Archived from the original on 2009-01-16. 
  5. ^ a b "Giant hogweed" (PDF). Center for Invasive Species and Ecosystem Health. USDA/University of Georgia. Retrieved 2011-07-06. 
  6. ^ Forney, Thomas; Miller, Glenn; Myers-Shenai Beth (27 May 2009). "Oregon Department of Agriculture Plant Pest Risk Assessment for Giant Hogweed Heracleum mantegazzianum" (PDF). Archived from the original (PDF) on 28 May 2010. 
  7. ^ a b Stace, C. A. (2010). New Flora of the British Isles (Third ed.). Cambridge, U.K.: Cambridge University Press. p. 450. ISBN 9780521707725. 
  8. ^ Parnell, J. and Curtis, T. 2012. Webb's An Irish Flora. Cork University Press. ISBN 978-185918-4783
  9. ^ a b c d e "Giant hogweed information". NetRegs. U.K. Government. Archived from the original on 2007-02-23. 
  10. ^ Collier, Mike (24 July 2017). "Things of Latvia: Latvānis". LSM. Retrieved 2 August 2017. 
  11. ^ "5 things you need to know about toxic hogweed". CBC News. 
  12. ^ Halfnight, Drew (July 13, 2010). "Giant weed that burns and blinds spreads across Canada". The National Post. 
  13. ^ a b "Plants profile for Heracleum mantegazzianum". 
  14. ^ "Heracleum mantegazzianum". 
  15. ^ "Giant hogweed: Not widely spread in Michigan". 
  16. ^
  17. ^ Diebel, Matthew (18 June 2018). "Giant Hogweed, a Plant That Can Cause Burns and Blindness, Found in Virginia". USA Today. 
  18. ^ Ducharme, Jamie (June 20, 2018). "A Giant Plant That Can Cause Blindness Was Spotted for the First Time in a New State". Time. New York. 
  19. ^ "Giant Hogweed" (PDF). Peterborough, Ont.: Ministry of Natural Resources and Forestry, Government of Ontario. p. 2. Retrieved July 15, 2018. 
  20. ^ "GIANT ALIEN — Result In Brief". Retrieved 2018-07-04. 
  21. ^ "Giant Hogweed (Heracleum mantegazzianum) - A pernicious invasive weed: Developing a sustainable strategy for alien invasive plant management in Europe". Retrieved 2018-07-04. 
  22. ^ "List of Invasive Alien Species of Union concern". Retrieved 2018-07-04. 
  23. ^ Wildlife & Countryside Act 1981 Section 14 and Schedule 9, Part II.
  24. ^ "Invasive and Noxious Weeds: Federal Noxious Weeds". Natural Resources Conservation Service. U.S. Department of Agriculture. 
  25. ^ "NYSDEC Giant Hogweed Control Program". New Paltz, N.Y.: New York State Department of Environmental Conservation. Archived from the original on May 6, 2015. 
  26. ^ "State confirms poisonous plant sightings". The Portland Press Herald. May 22, 2012. Retrieved 2015-06-21. 

External linksEdit