Heracleum mantegazzianum - Sommier & Levier
Giant Hogweed
Taxonomic Status: Accepted
Related ITIS Name(s): Heracleum mantegazzianum Sommier & Levier (TSN 502954)
French Common Names: berce du Caucase
Unique Identifier: ELEMENT_GLOBAL.2.153454
Element Code: PDAPI15020
Informal Taxonomy: Plants, Vascular - Flowering Plants - Carrot Family
 
Kingdom Phylum Class Order Family Genus
Plantae Anthophyta Dicotyledoneae Apiales Apiaceae Heracleum
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Concept Reference
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Concept Reference: Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
Concept Reference Code: B94KAR01HQUS
Name Used in Concept Reference: Heracleum mantegazzianum
Conservation Status
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NatureServe Status

Global Status: GNR
Global Status Last Changed: 22Mar1994
Rounded Global Status: GNR - Not Yet Ranked
Nation: United States
National Status: NNA
Nation: Canada
National Status: NNA (02Nov2012)

U.S. & Canada State/Province Status
United States Maine (SNA), Michigan (SNA), New York (SNA), Pennsylvania (SNA), Washington (SNA)
Canada British Columbia (SNA), New Brunswick (SNA), Nova Scotia (SNA), Ontario (SNA), Prince Edward Island (SNA)

Other Statuses

NatureServe Global Conservation Status Factors

Other NatureServe Conservation Status Information

Distribution
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U.S. States and Canadian Provinces
Color legend for Distribution Map
NOTE: The distribution shown may be incomplete, particularly for some rapidly spreading exotic species.

U.S. & Canada State/Province Distribution
United States MEexotic, MIexotic, NYexotic, PAexotic, WAexotic
Canada BCexotic, NBexotic, NSexotic, ONexotic, PEexotic

Range Map
No map available.

Ecology & Life History Not yet assessed
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Economic Attributes Not yet assessed
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Management Summary Not yet assessed
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Population/Occurrence Delineation Not yet assessed
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Population/Occurrence Viability
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U.S. Invasive Species Impact Rank (I-Rank)
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Disclaimer: While I-Rank information is available over NatureServe Explorer, NatureServe is not actively developing or maintaining these data. Species with I-RANKs do not represent a random sample of species exotic in the United States; available assessments may be biased toward those species with higher-than-average impact.

I-Rank: Medium/Low
Rounded I-Rank: Medium
I-Rank Reasons Summary: Heracleum mantegazzianum forms a dense canopy and once established, crowds out native plant species and reduce species richness. It has invaded riparian areas and also occurs on disturbed sites. Its current range is restricted to relatively small areas within certain states. However, it appears to have the potential to expand substantially and has been found in a number of new states in the last few years.
Subrank I - Ecological Impact: Medium/Low
Subrank II - Current Distribution/Abundance: Medium/Low
Subrank III - Trend in Distribution/Abundance: High/Medium
Subrank IV - Management Difficulty: Medium
I-Rank Review Date: 06Jan2004
Evaluator: Tomaino, A.
Native anywhere in the U.S?
Native Range: Eurasia (Swearingen et al. 2002), Caucasus Mountains and southwestern Asia (WA State 2003).

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Screening Questions

S-1. Established outside cultivation as a non-native? YES
Comments: Established outside cultivation (Kartesz 1999).

S-2. Present in conservation areas or other native species habitat? Yes
Comments: Establishes along stream banks (WA State 2003).

Subrank I - Ecological Impact: Medium/Low

1. Impact on Ecosystem Processes and System-wide Parameters:Low significance
Comments: Increases soil erosion along the stream banks where it occurs (WA State 2003). On riverbanks, large stands may destabilize the soil and increase soil erosion (Weber 2003).

2. Impact on Ecological Community Structure:Moderate significance
Comments: Attains a maximum height of 4 to 5 m which is taller than our native herbaceous vegetation (Case and Beaman 1992), thus creating a new layer.

3. Impact on Ecological Community Composition:Medium/Low significance
Comments: It forms a dense canopy and once established, crowds out native plant species (WA State 2003). Forms extensive populations whose large rosettes crowd out native species and reduce species richness (Weber 2003).

4. Impact on Individual Native Plant or Animal Species:Unknown

5. Conservation Significance of the Communities and Native Species Threatened:Medium significance/Insignificant
Comments: Occurs in riparian habitats, which could be of high quality, as well as disturbed sites such as roadsides, rights-of-way, and vacant lots (WA State 2003).

Subrank II. Current Distribution and Abundance: Medium/Low

6. Current Range Size in Nation:Moderate significance
Comments: Occurs in Maine, New York, Pennsylvania, Michigan, and Washington state according to Kartesz (1999). Kartesz (2002 draft) reports from three additional states Connecticut, Illinois, and Oregon. Also reported from Massachusetts, Vermont, and Maryland but it is unknown whether it occurs in conservation areas in these states (Cooperative Agriculture Pest Survey Program 2003).

7. Proportion of Current Range Where the Species is Negatively Impacting Biodiversity:Medium significance/Insignificant
Comments: Reported from several locations in western Washington State, especially in the Seattle area (WA State 2003). One site known in Michigan as of 1992 (Case and Beaman 1992). It occurs in Oregon, but is currently under eradication or is restricted to a small area (Systma 2003).

8. Proportion of Nation's Biogeographic Units Invaded:Medium/Low significance
Comments: At most 30% of units, based on Kartesz (1999) and TNC (2001).

9. Diversity of Habitats or Ecological Systems Invaded in Nation:Insignificant
Comments: It has invaded river or stream edges, and floodplain forest (Mehrhoff et al. 2003), so only riparian habitats .

Subrank III. Trend in Distribution and Abundance: High/Medium

10. Current Trend in Total Range within Nation:High significance
Comments: The spread of this plant appears to be slow but steady (WA State 2003). The number and size of populations in the Seattle area, where it has been observed over the past four years, continue to grow annually (WA State 2003). From Kartesz (1999) to Kartesz (2002 draft) its range has increased by three states, one from the northeast, one in the midwest, and one in the northwest.

11. Proportion of Potential Range Currently Occupied:Moderate significance
Comments: Roughly 10-30%, based on USDA (1990).

12. Long-distance Dispersal Potential within Nation:Medium/Low significance
Comments: Wind tunnel experiments have shown that wind could account for short-distance dispersal but would not explain long-distance dispersal (Case and Beaman 1992). Experiments in Scotland were unable to document any instance where birds were taking the seeds, even when these were deliberately set out with other food items (Clegg and Grace 1974 in Case and Beaman 1992). Water dispersal was studied and it was found that fruits can remain afloat for three days (Clegg and Grace 1974 in Case and Beaman 1992). Giant hogweed seeds were found to travel 10-50 meters by wind but further when water is the transport mechanism (Caffrey 1994 in Mayer 1999).

13. Local Range Expansion or Change in Abundance:High/Low significance
Comments: The number and size of populations in the Seattle area, where it has been observed over the past four years, continue to grow annually (WA 2003). It was confirmed as a new state record in Connecticut in 2001 (CIPWG 2003). As of August 2003, it has been found in 16 towns and 6 counties in Connecticut (CIPWG 2003). It is unknown when these sites originated but it is apparently expanding. The species forms extensive populations whose large rosettes crowd out native species (Weber 2003).

14. Inherent Ability to Invade Conservation Areas and Other Native Species Habitats:Moderate significance
Comments: It is water dispersed and establishes along streams and rivers and in floodplain forests (Mehrhoff et al. 2003). Riparian habitats may be likely to have some disturbances but it does not seem to establish only in areas where major disturbance has occurred in the last 20 years.

15. Similar Habitats Invaded Elsewhere:Moderate significance
Comments: It is a problem in Europe where it has followed a similar pattern in all countries, moving from gardens to riparian zones and then to forest edges, and meadows (Mayer 1999). It was found that once giant hogweed does establish in terrestrial areas it actually prefers terrestrial areas to riparian zones (Mayer 1999). In the Czech republic in 1950, 66.7% of giant hogweed was in riparian areas but in 1990, only 26.4% of giant hogweed populations were in riparian zones (Pysek 1994 in Mayer 1999). In the United States, the conservation areas that giant hogweed is most common in are riparian habitats and it is considered an invasive freshwater weed (WA 2003). Its behavior in Europe suggests it could invade terrestrial habitats in the United States.

16. Reproductive Characteristics:High significance
Comments: Each plant may produce up to 120,000 seeds (Dodd 1994 in Mayer 1999). Seeds can remain viable in the soil for up to 7 years (Anderen 1994 in Mayer 1999). It also has a persistent root stalk and reproduces vegetatively from perennating buds (WA State 2003). If the plant is cut, it can regrow quickly from the auxilliary buds (Caffrey 1994 in Mayer 1999). It also has hermaphorditic flowers which allows it to reproduce asexually (Caffrey 1999 in Mayer 1999).

Subrank IV. General Management Difficulty: Medium

17. General Management Difficulty:Moderate significance
Comments: It is very difficult to control (Swearingen et al. 2002). Chemical treatment is the most used and most effective (Mayer 1999). Mechanical removal is not as effective and is dangerous due to the poisonous sap the plant exudes (Mayer 1999). In most studies, chemical treatment resulted in greater than 80% mortality with a small reestablishment of giant hogweed the following growing season (Mayer 1999). There is a need for long term monitoring and management as seeds can remain viable in the soil for up to 7 years and if nearby seed sources are not eliminated the plant could become reestablished (CIPWG; Mayer 1999).

18. Minimum Time Commitment:Moderate significance
Comments: Seeds can remain viable in the soil for up to 7 years (Anderen 1994 in Mayer 1999).

19. Impacts of Management on Native Species:Medium/Low significance
Comments: Glyphosate is considered the safest and only effective chemical treatment for giant hogweed in riparian zones (Mayer 1999). Within four weeks of application, native grasses were growing on triclophyr sites, whereas no vegetation grew on sites treated with glyphosate (Caffrey 1994 in Mayer 1999). Glyphosate should be used cautiously around desirable species since it is nonselective (WA State 2003). Mechanical treatment is another option, although less effective than chemcial treatment in the short-term, if done persistently it is effective (Mayer 1999).

20. Accessibility of Invaded Areas:Insignificant
Comments: The plant exudes a sap which causes severe burns to skin and scaring (WA State 2003); eye contact may result in blindness (CIPWG 2003). Landowners who are aware of these health hazards would welcome treatment.
Authors/Contributors
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Botanical data developed by NatureServe and its network of natural heritage programs (see Local Programs), The North Carolina Botanical Garden, and other contributors and cooperators (see Sources).

References
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  • Case, M. A., and J. H. Beaman. 1992. Heracleum mantegazzianum (giant cow parsnip): another exotic in the Michigan flora. Michigan Botanist 31: 152-154.

  • Connecticut Invasive Plant Working Group (CIPWG). 2003. August-last update. Giant Hogweed in Connecticut. Online. Available: http://www.hort.uconn.edu/CIPWG. Accessed 2004, January 7.

  • Cooperative Agriculture Pest Survey Program. 2003. December 23-last update. National Agricultural Pest Information System (NAPIS), Pest Information for Giant Hogweed (Heracleum mantegazzianum). Online. Available: http://www.ceris.purdue.edu/napis/pests/index.html. Accessed 2004, January 7.

  • Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.

  • Kartesz, J.T. 1999. A synonymized checklist and atlas with biological attributes for the vascular flora of the United States, Canada, and Greenland. First edition. In: Kartesz, J.T., and C.A. Meacham. Synthesis of the North American Flora, Version 1.0. North Carolina Botanical Garden, Chapel Hill, N.C.

  • Kartesz, J.T. 2002. A synonymized checklist and atlas with biological attributes for the vascular flora of the United States, Canada, and Greenland. Second edition (including county distribution). In: Kartesz, J.T., and C.A. Meacham. Synthesis of the North American Flora, Draft of Version 2.0. North Carolina Botanical Garden, Chapel Hill, N.C.

  • Mayer, L. K. 2000. Comparison of management techniques for Heracleum mantegazzianum in north and central Europe. Restoration and Reclamation Review 6. On-Line Journal. Available: http://www.hort.agri.umn.edu/h5015/rrr.htm. Accessed 2004, January 6.

  • Mehrhoff, L.J., J.A. Silander, Jr., S.A. Leicht and E. Mosher. 2003. IPANE: Invasive Plant Atlas of New England. Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT. Online. Available: http://invasives.eeb.uconn.edu/ipane/.

  • Swearingen, J., K. Reshetiloff, B. Slattery, and S. Zwicker. 2002. Plant Invaders of Mid-Atlantic Natural Areas. National Park Service and U.S. Fish & Wildlife Service, 82 pp.

  • Systma, M. 2003. Invasive Species in Oregon Report Card 2003. Oregon Invasive Species Council. Online. Available: www.oda.state.or.us/plant/Inv_spp. (accessed 2004).

  • The Nature Conservancy. 2001. Map: TNC Ecoregions of the United States. Modification of Bailey Ecoregions. Online . Accessed May 2003.

  • USDA Agricultural Research Service. 1990. USDA Plants Hardiness Zone Map. Misc. Publ. Number 1475.

  • Washington State Noxious Weed Control Board. 2003. September 2 last update. Written findings of the State Noxious Weed Control Board for giant hogweed (Heracleum mantegazzianum) Class A Weed. Online. Available: http://www.nwcb.wa.gov/weed_info/hogweed.html. Accessed 2004, January 6.

  • Weber, E. 2003. Invasive plant species of the world: a reference guide to environmental weeds. CABI Publishing, Cambridge, Massachusetts. 548 pp.

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