Fact Sheets


Heracleum mantegazzianum Sommier & Levier

Family :

Famille :


Synonym(s) :

Synonyme(s) :

Heracleum grossheimii Manden. (Page et al. 2006; CABI 2022; POWO 2022)

Common Name(s) :

Nom(s) commun(s) :

Giant Hogweed
(English) (GC 2016; CABI 2022; USDA-ARS 2022)
Berce du Caucase (French) (Page et al. 2006; GC 2016)
Cartwheel-flower (English) (Page et al. 2006; USDA-ARS 2022)
Giant cow-parsnip (English) (Page et al. 2006)
Boršcevik drevovidnyj (Russian) (CABI 2022)

  • Heracleum mantegazzianum (giant hogweed) mericarps

  • Heracleum mantegazzianum (giant hogweed) mericarps

  • Heracleum mantegazzianum (giant hogweed) mericarp; outer side

  • Heracleum mantegazzianum (giant hogweed) mericarp; inner side

  • Heracleum mantegazzianum (giant hogweed), teeth along the edge of mericarp, especially near the top of the fruit

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Regulation :

Remarques Réglementation:

  • CFIA Weed Seeds Order - Class 2: Primary Noxious Weed Seeds
  • Quarantine lists of countries e.g. Mexico *may be updated without notice
  • USA Federal Noxious Weed List
  • USA Federal Noxious Weed Seed List

Regulation Notes:

Distribution :

Répartition :

The species is native to the Caucasus region of Asia (i.e., Georgia and southern Russia) and introduced into Europe, North America, Australia and New Zealand (USDA-ARS 2022).

H. mantegazzianum is found in the northeastern United States and the Pacific northwest (Page et al. 2006). In Canada, this species occurs in British Columbia, Ontario, Quebec, New Brunswick, Newfoundland, Nova Scotia, and Prince Edward Island (Brouillet et al. 2010+).

Habitat and Crop Association :

Habitat et Cultures Associées :

Fields, gardens, pastures, grasslands, open forests, forest edges, forested floodplains, shorelines, ditches, landfills, gravel bars, roadsides and urban parks (Darbyshire 2003; Page et al. 2006). Not a common agricultural weed (Page et al. 2006).

Economic Use, cultivation area, and Weed Association :

Utilisation économique, zone de culture et association de mauvaises herbes :

Duration of Life Cycle :

Durée du cycle vital:


Dispersal Unit Type :

Type d’unité de dispersion :

Schizocarp, divided into 2 mericarps

General Information


H. mantegazzianum was planted in European botanical gardens of the early 19th century as an ornamental and was first recorded in Canada in 1949 in Ontario (Page et al. 2006). It favours regions with cool, moist climates and soils with high organic matter (Page et al. 2006; CABI 2022).

H. mantegazzianum plants generally remain vegetative as a rosette for three to five years prior to flowering (CABI 2022). The plants usually die following seed production (Page et al. 2006; CABI 2022). One plant alone reportedly produced over one hundred thousand seeds (Page et al. 2006).

Plant tissues contain toxic furanocoumarins, concentrated in the flowers and the oil ducts of the seeds. These chemicals can cause burns when skin or eyes is exposed to UV radiation or sunlight in both humans and livestock (Cain et al 2010).


Heracleum mantegazzianum infestation (Jan Samanek, Phytosanitary Administration, Bugwood.org)



  • Mericarp


    • Mericarp length*: 7.3 – 11.5 mm; width: 5.4 – 7.6 mm
    *Note: minimum and maximum of 20 mericarps in a normal range of this species using image measurement (ISMA 2020)

    Measurements from literature:

    • Length: 6–18 mm; width: 4–10 mm (Page et al. 2006)
    • Length: 10.6–11.6 mm; width: 5.8–6.2 mm (Klimko et al. 2013)
    • Length: (7) 9-12 (14) mm; width: (5) 6-8 (11) mm (Scher et al. 2015)


    • Long oval, egg-shaped or heart-shaped mericarp, flattened and winged around the outside

    Surface Texture

    • Mericarp surface generally smooth, but may have scattered short hairs (pubescence) on some mericarps
    • One side of the mericarp has five threadlike ribs, while the other side has two running from one end to the other (Scher et al. 2015)
    • Spines generally occur along the edge of the mericarp, especially near the pointed end
    • Viewing with a scanning electron microscope, the mericarp’s outer side is reticulate (slightly ridged) with thin walls and cells elongated in one plane (Klimko et al. 2013)


    • Mericarps dull or shiny straw yellow or brown with reddish-brown oil ducts
    • Four oil ducts (vittae) are visible on the mericarp’s outer side (Page et al. 2006; Klimko et al. 2013), sometimes up to six (Page et al. 2006), and two on the inner side

    Other Features

    Mericarp end with style remnant

    • Style remnant is short and triangular shaped
    • A piece of connective tissue from between the mericarps may remain attached to the style remnant
    • Generally a shallow notch along the edge of the mericarp on either side of the style remnant

    Mericarp end opposite style remnant

    • The curved end opposite the style remnant is slightly curled towards one side

    Other features

    • The oil ducts on the outer side generally extend 3/4 down the mericarp and have enlarged ends, and the inner side ones are generally shorter
    • The oil in the fruit and seed is a strong irritant (Page et al. 2006)
  • Seed


    • Seed length: 6.1 – 7.1 mm; width: 4.0 – 4.4 mm (Klimko et al. 2013)


    • Seed is oval shaped, flattened in edge view
    • Oil ducts may remain attached to the seed, or be removed with the fruit wall

    Surface Texture

    • Seed is smooth


    • Seed is brownish or dark grey coloured

    Other Features

    • Seed coat thin, transparent, adhering to the fruit wall
    • A portion of the oil ducts remain fused to the seed when the fruit wall is removed
    • The oil in the fruit and seed is a strong irritant (Page et al. 2006)
  • Embryo


    • Embryo rudimentary size


    • Embryo is linear


    • Endosperm is soft and oily, translucent grey coloured

    Other Features

    • Embryo is in a basal position

Identification Tips


Several genera within the Apiaceae have straw yellow coloured fruits that are flattened with longitudinal reddish oil ducts, e.g. Heracleum, Aethusa, Angelica and Pastinaca. Heracleum mantegazzianum mericarps have a deep notch at the end with the style remnant, teardrop-shaped oil ducts, teeth along the edge and surface hair may be present or absent (glabrous or pubescent). These features of H. mantegazzianum mericarps generally look similar to Heracleum sosnowskyi and H. persicum mericarps with many overlapping features, but can be separated from H. sphondylium subsp. montanum primarily by the shape of the oil ducts.


Additional Botany Information



  • Flowers have whitish petals (rarely pinkish), up to 1.0 cm in size, the style remnant is cap-like and remains on the fruit at the pointed end (Page et al. 2006).
  • The inflorescence is a compound umbel (Page et al. 2006)

Vegetative Features

  • Stems are ridged, hollow, and 4 – 10 cm wide (Page et al. 2006)
  • Compound leaves are arranged alternately along the stem (Page et al. 2006)
  • Stiff, white hairs cover vegetative plant parts except for the upper surfaces of the leaves (Page et al. 2006)
  • Plants can reach heights of 5.5 metres (Page et al. 2006)
  • Plants exude a musty or resinous smell, especially when broken (Page et al. 2006)

Similar Species


Similar species are based on a study of seed morphology of various species, and those with similar dispersal units are identified. The study is limited by physical specimen and literature availability at the time of examination, and possibly impacted by the subjectivity of the authors based on their knowledge and experience. Providing similar species information for seed identification is to make users aware of similarities that could possibly result in misidentification.

Heracleum sphondylium subsp. montanum (Schleich. ex Gaudin) Briq. (cow-parsnip )

H. sphondylium subsp. montanum mericarps are a similar size (length*: 6.6 – 12.5 mm; width: 4.9 – 8.6 mm) but lack hairs or spines along the edge, and have more narrow oil ducts than H. mantegazzianum.

* Note: minimum and maximum of 20 mericarps in a normal range of this species using image measurement (ISMA 2020)

Heracleum sosnowskyi Manden. (hogweed)

H. sosnowskyi mericarps are a variable size that can overlap with H. mantegazzianum mericarps. Other features of H. sosnowskyi mericarps, such as shape, pubescence, marginal spines and vittae (oil ducts) tend to overlap with H. mantegazzianum, making them difficult to distinguish under optical microscope magnification (up to 60x).
Viewing with a scanning electron microscope, H. sosnowskyi mericarp’s outer side is ridged reticulate with thick walls, compared to the with thin walls and elongated cells seen in H. mantegazzianum (Klimko et al. 2013).
Measurements of H. sosnowskyi mericarps:

• Length*: 4.5 – 9.9 mm; width: 3.6 – 7.9 mm (CFIA-SSTS)
• Length: 10.7 – 14.4 mm; width: 7.0 – 9.8 mm (Klimko et al. 2013)

* Note: minimum and maximum of 10 mericarps in a normal range of this species using image measurement (ISMA 2020)

Heracleum persicum Desf.

H. persicum is native to Iran, Turkey and Iraq but is invading many countries in Europe, including northern European countries of Denmark, Finland, Iceland, Norway and Sweden (Sachajdakiewicz and Bzdęga 2017; CABI 2022). H. persicum was introduced as an ornamental, but may also be spread by demand for its seeds, which are ground for use as a spice (Asgarpanah et al. 2012; Sachajdakiewicz and Bzdęga 2017; CABI 2022) and for medicinal purposes (Asgarpanah et al. 2012; CABI 2022).

Unlike H. mantegazzianum and H. sosnowskyi, plants of H. persicum are perennial and do not die following seed production and are able to reproduce vegetatively. H. persicum plants exude an anise-like smell (Kabuce and Priede 2010; CABI 2022) and not the resinous or musty smell of H. mantegazzianum (Page et al. 2006).

Mericarps may overlap in size (length: 7 – 8 mm (Asgarpanah et al. 2012), length: 8 – 14 mm; width: 6 – 9.5 mm (CABI 2022)) with those of H. mantegazzianum. Generally, H. persicum mericarp’s oil glands are only slightly wider at one end (Asgarpanah et al. 2012; CABI 2022) compared to those of H. mantegazzianum that are noticeably swollen at one end.

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Asgarpanah J., Dadashzadeh Mehrabani G., Ahmadi M, Ranjbar R. and Safi-Aldin Ardebily M. 2012. Chemistry, pharmacology and medicinal properties of Heracleum persicum Desf. Ex Fischer: A review. Journal of Medicinal Plants Research Vol. 6(10), pp. 1813-1820.

Brouillet, L., Coursol, F., Meades, S. J., Favreau, M., Anions, M., Bélisle, P. and Desmet, P. 2010+. VASCAN, the database of vascular plants of Canada. http://data.canadensys.net/vascan/ Accessed June 1, 2021.

Centre for Agriculture and Bioscience International (CABI). 2022. Invasive Species Compendium, CAB International, Wallingford, UK. https://www.cabidigitallibrary.org/journal/cabicompendium Accessed June 01, 2022.

Darbyshire, S. J. 2003. Inventory of Canadian Agricultural Weeds. Agriculture and Agri-Food Canada, Research Branch. Ottawa, ON.

Government of Canada (GC). 2016. Canadian Weed Seeds Order. https://laws-lois.justice.gc.ca/eng/regulations/SOR-2016-93/page-2.html (English) https://laws-lois.justice.gc.ca/fra/reglements/DORS-2016-93/page-2.html (French)

International Seed Morphology Association (ISMA). 2020. Method for Seed Size Measurement. Version 1.0. ISMA Publication Guide.

Kabuce, N. and Priede, N. 2010. NOBANIS – Invasive alien species fact sheet – Heracleum sosnowskyi. Online Database of the European Network on Invasive Alien Species – NOBANIS, http://www.nobanis.org/Factsheets.asp Accessed September 3, 2021.

Klimko M., Truchan M., and Wysakowska I., 2013. Fruit and seed morphology of the genus Heracleum L. (Apiaceae) in Poland. Roczniki Akademii Rolniczej w Poznaniu. Botanika – Steciana 17: 13-24.

Page, N. A., Wall, R. E., Darbyshire, S. J. and Mulligan, G. A. 2006. The Biology of Invasive Alien Plants in Canada. 4. Heracleum mantegazzianum Sommier & Levier. Canadian Journal of Plant Science 86: 569–589.

Plants of the World Online (POWO). 2022. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet; http://www.plantsoftheworldonline.org/ Accessed June 01, 2022.

Sachajdakiewicz, I. and Bzdęga, K. 2017. Harmonia+PL – procedure of negative impact risk assessment for invasive alien species and potentially invasive alien species in Poland (Appendix A). http://projekty.gdos.gov.pl/files/artykuly/127062/Heracleum-persicum-Barszcz-perski-EN_icon.pdf

Scher, J. L., D. S. Walters, and A.J. Redford. 2015. Federal noxious weed disseminules of the U.S., Edition 2.2. California Department of Food and Agriculture, and USDA APHIS Identification Technology Program. Fort Collins, CO. http://idtools.org/id/fnw Accessed July 27, 2022.

U.S. Department of Agriculture-Agricultural Research Services (USDA-ARS). Germplasm Resources Information Network – (GRIN), https://npgsweb.ars-grin.gov/gringlobal/taxon/taxonomysimple.aspx Accessed June 01, 2022.



Jennifer Neudorf, Angela Salzl, Ruojing Wang, Karen Castro, Katrina Entwistle

Canadian Food Inspection Agency