Heracleum mantegazzianum

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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 plant in the family Apiaceae. In New Zealand, it is also sometimes called wild parsnip,[2] or wild rhubarb.[2] It typically grows to heights of 2–5.5 m (6 ft 7 in–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, long-lasting scars, and if it comes in contact with eyes, blindness. These serious reactions are due to the furocoumarin derivatives in the leaves, roots, stems, flowers, and seeds of the plant.


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 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 Western Europe and North America[edit]

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 also spread in the northeastern and northwestern United States, and southern Canada. It is equally a pernicious invasive species in Germany, France, and Belgium, overtaking the local species.[9]

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.[10] 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.[11]

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.[12][13] It is also recorded occasionally in Michigan[14] It is a federally listed noxious weed in many states.[12]


Giant hogweed (close-up)

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] The presence of minute amounts of sap in the eyes can lead to temporary or even permanent blindness.[15][better source needed]

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 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. 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][16] 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.[17] 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, including reporting, database maintenance, and crews for removal or herbicide control.[18][19] 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.[20]

In popular culture[edit]

On the 1971 album Nursery Cryme by the progressive rock group Genesis, the track "The Return of the Giant Hogweed" warns of the spread of H. mantegazzianum after the plant was first "captured" in Russia and brought to England by a Victorian explorer.[21]

See also[edit]


  1. ^ a b John H. Wiersema. "USDA GRIN taxonomy". Ars-grin.gov. Retrieved 2013-08-06. 
  2. ^ a b c d "(New Zealand) National Pest Plant Accord 2008" (PDF). 2008. p. 61. Retrieved 2015-06-21. 
  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. 
  5. ^ a b "Giant hogweed" (PDF). Center for Invasive Species and Ecosystem Health. USDA/University of Georgia. Retrieved 2011-07-06. 
  6. ^ Thomas Forney, Glenn Miller, and Beth Myers-Shenai (2009). "Oregon Department of Agriculture Plant Pest Risk Assessment for Giant Hogweed Heracleum mantegazzianum" (PDF). 
  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.  Cite error: Invalid <ref> tag; name "Stace" defined multiple times with different content (see the help page).
  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. ^ "5 things you need to know about toxic hogweed". CBC News. 
  11. ^ Halfnight, Drew (July 13, 2010). "Giant weed that burns and blinds spreads across Canada". The National Post. 
  12. ^ a b "Plants profile for Heracleum mantegazzianum". 
  13. ^ "Heracleum mantegazzianum". 
  14. ^ "Giant hogweed: Not widely spread in Michigan". 
  15. ^ "Toxic weed discovered in Ottawa". CBC. 2010-07-13. Retrieved 2014-08-14. 
  16. ^ Wildlife & Countryside Act 1981 Section 14 and Schedule 9, Part II.
  17. ^ "Invasive and Noxious Weeds: Federal Noxious Weeds". Natural Resources Conservation Service. U.S. Department of Agriculture. 
  18. ^ "Giant Hogweed". NYS Dept. of Environmental Conservation. Retrieved 2015-06-21. 
  19. ^ "Beware Giant Hogweed brochure" (PDF). New York State Department of Environmental Conservation. Retrieved 2015-06-20. 
  20. ^ "State confirms poisonous plant sightings". The Portland Press Herald. May 22, 2012. Retrieved 2015-06-21. 
  21. ^ Austin, Jon (18 July 2015). "WATCH: Did Genesis bizarrely predict Britain's Giant Hogweed nightmare 44 years ago?". Daily Express (Northern and Shell Media Publications.). Retrieved 6 August 2015. 

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