E-Flora BC: Electronic Atlas of the Flora of British Columbia

Heracleum mantegazzianum Sommier & Lev.
giant cow-parsnip (giant hogweed; hogweed)
Apiaceae

Introduction to Vascular Plants

© Hugh Griffith  Email the photographer   (Photo ID #1155)

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Distribution of Heracleum mantegazzianum
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Introduction

Giant hogweed (a.k.a. giant cow parsnip) is native to the Caucasus region and is introduced and invasive in Europe and North America (Krinke et al. 2005) where it is found in moist to wet disturbed sites. In North America, it is reported from several US states (CT, IL, ME, MI, NY, OR, PA, WA) and some Canadian provinces (BC, NB, ON, QC) (USDA 2010). In British Columbia, it is found in the southwestern corner of the province, along the eastern edge of Vancouver Island, on the Gulf Islands, and in the Lower Mainland. It has recently been reported in the Kootenays in the southeastern region of the province.

Giant hogweed belongs to the genus Heracleum in the the carrot family (Apiaceae). This genus consists of about 80 species worldwide (found in Eurasia, east Africa, 1 in North America), and is comprised of biennial or perennial herbs with taproots or clustered roots; species in the genus may be glabrous or hairy with erect stems that are usually branched, thick, and hollow (Ganders 2010).

Giant hogweed is generally a tall (1.5-5 m), distinctive species that is readily recognized by its large terminal umbels of white flowers and large leaves that are deeply divided into three palmately-lobed segments. It produces abundant seed (20,000 seeds per plant), and dies back after flowering and seed set (Marrison and Goerig 2010?).

Giant hogweed is a species of concern, and a target for eradication, because it is phototoxic and can cause serious burns and painful blisters. We strongly recommend that you do not handle this plant. Read a fact sheet for this species and view videos to learn more about its toxicity and how to recognize it: 1) the story of giant hogweed 2) giant hogweed on the River Tweed 3) giant hogweed in Vermont

Species Information

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General:
Similar to H. lanatum except: Biennial to perennial. Stem (1.5) 2-4.5 m tall, up to 10 cm in diameter, usually with purple blotches.
Stems:
Stem (1.5) 2-4.5 m tall, up to 10 cm in diameter, usually with purple blotches.
Leaves:
Leaves up to 3 m long, blade to 2.6 cm wide, ternately or pinnately divided, lateral segments pinnately lobed, short-hairy below.
Flowers:
Inflorescence, larger ones, 20-50 cm in diameter, rays 50-150. Petals white or rarely pinkish.
Fruits:
Fruit blunt and rounded toward base.
Notes:
This plant can cause severe dermatitis when handled.

Account Author::  Fred Ganders, 2010.

Habitat / Range

Habitat wet to moist disturbed areas in the lowlands, garden escape, well established in Vancouver, North Vancouver, West Vancouver, native to Asia.

Source: The Illustrated Flora of British Columbia

Additional Notes

For further information about control of this species, visit the Great Vancouver Invasive Plant council web site. It is listed by them as one of the top twelve species of concern in the Vancouver Region. It is also listed by the Coastal Invasive Plant Council as one of the top fourteen species of concern on Vancouver Island and adjacent coastal areas. Visit their web site.

Climate

The climate type for this species, as reported in the: "British Columbia plant species codes and selected attributes. Version 6 Database" (Meidinger et al. 2008), is not evaluated, unknown or variable.

Taxonomic and Nomenclatural Links

Additional Photo Sources

Related Databases

Species References

Ganders, Fred. 2010. Personal communication. Unpublished material.

Krinke, Lukas, Lenka Moravcováa, Petr Pyšeka, Vojtech Jarošíka, Jan Pergla and Irena Perglováa. 2005. Seed bank of an invasive alien, Heracleum mantegazzianum, and its seasonal dynamics. Seed Science Research 15: 239 to 248.

Marrison, David L. and David J. Goerig. 2010?. Giant Hogweed (Heracleum mantegazzianum) Fact Sheet. Ohio State University Extension Fact Sheet. Available Online.

USDA. 2010. Plant profile for Heracleum mantegazzianum. United States Department of Agriculture Plants Database. Available Online.

General References