Weed Seed: Heracleum mantegazzianum (Giant hogweed)
Primary Noxious, Class 2 in the Canadian Weed Seeds Order, 2016 under the Seeds Act.
Canadian: Occurs in BC, ON, QC, NB, NL, NS (Page et al. 2006Footnote 1).
Worldwide: Native to the Caucasus region of Asia (Georgia, Russia) and introduced in Europe, North America, Australia and New Zealand (USDA-ARS 2016Footnote 2).
Duration of Life Cycle
Monocarpic perennial (dies after flowering)
Seed or fruit type
Schizocarp, divided into 2 mericarps
- Mericarp length: 6.0 - 18.0 mm
- Mericarp width: 4.0 - 10.0 mm
- Long oval-shaped mericarp, flattened
- Mericarp smooth, dull
- Mericarp straw yellow with reddish oil ducts
- Teeth along the edge, especially near the top of the mericarp
- The oil ducts extend 3/4 down the mericarp and have enlarged ends
- The ventral side of the style remnant at the top of the mericarp is M-shaped
Habitat and Crop Association
Fields, gardens, pastures, grasslands, open forests, forest edges, forested floodplains, shorelines, ditches, landfills, gravel bars, roadsides and urban parks (Darbyshire 2003Footnote 3, Page et al. 2006Footnote 1). Not a common agricultural weed (Page et al. 2006Footnote 1).
Giant hogweed 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. 2006Footnote 1). It favours regions with cool, moist climates and soils with high organic matter (Page et al. 2006Footnote 1, CABI 2016Footnote 4).
Cow parsnip (Heracleum sphondylium subsp. montanum)
- Cow parsnip mericarps are similar size, oval shape, reddish oil ducts and straw yellow colour as giant hogweed.
- Cow parsnip mericarps have an arrow shape on the ventral side of the style remnant, no teeth on the margin, and have thinner oil ducts compared to giant hogweed.
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