Heracleum mantegazzianum (giant hogweed)
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PicturesTop of page
|Caption||Heracleum mantegazzianum (giant hogweed); urban infestation showing habit. Plants can reach 5m in height, with flower umbels up to 50cm in diameter. (Note person for scale.) Stevenage, Hertfordshire, UK.|
|Copyright||©Richard H. Shaw/CABI BIOSCIENCE|
|Habit||Heracleum mantegazzianum (giant hogweed); urban infestation showing habit. Plants can reach 5m in height, with flower umbels up to 50cm in diameter. (Note person for scale.) Stevenage, Hertfordshire, UK.||©Richard H. Shaw/CABI BIOSCIENCE|
|Caption||Heracleum mantegazzianum (giant hogweed); inflorescence and flowers. Suffolk, UK.|
|Copyright||©Chris Parker/Bristol, UK|
|Inflorescence||Heracleum mantegazzianum (giant hogweed); inflorescence and flowers. Suffolk, UK.||©Chris Parker/Bristol, UK|
|Caption||Heracleum mantegazzianum (giant hogweed) flowering plant. Suffolk, UK, 2003.|
|Copyright||©Chris Parker/Bristol, UK|
|Habit||Heracleum mantegazzianum (giant hogweed) flowering plant. Suffolk, UK, 2003.||©Chris Parker/Bristol, UK|
|Caption||Heracleum mantegazzianum (giant hogweed); flowering plant. Suffolk, UK.|
|Copyright||©Chris Parker/Bristol, UK|
|Habit||Heracleum mantegazzianum (giant hogweed); flowering plant. Suffolk, UK.||©Chris Parker/Bristol, UK|
|Caption||Heracleum mantegazzianum (giant hogweed); urban infestation showing typical habit. (Note person for scale) Stevenage, Hertfordshire, UK.|
|Copyright||©Richard H. Shaw/CABI BIOSCIENCE|
|Infestation||Heracleum mantegazzianum (giant hogweed); urban infestation showing typical habit. (Note person for scale) Stevenage, Hertfordshire, UK.||©Richard H. Shaw/CABI BIOSCIENCE|
|Caption||Heracleum mantegazzianum (giant hogweed); habit, showing developing leaves. In leeward coastal dune vegetation, showing its vegetative habit before inflorescences emerge. Nr Den Hague, Netherlands. May 2016.|
|Habit||Heracleum mantegazzianum (giant hogweed); habit, showing developing leaves. In leeward coastal dune vegetation, showing its vegetative habit before inflorescences emerge. Nr Den Hague, Netherlands. May 2016.||©Andrew Praciak-2016|
IdentityTop of page
Preferred Scientific Name
- Heracleum mantegazzianum Sommier & Levier (1895)
Preferred Common Name
Other Scientific Names
- Heracleum asperum M. Bieb. (1819)
- Heracleum caucasicum Steven (1812)
- Heracleum circassicum Mandenova (1970)
- Heracleum giganteum Fischer ex Hornem. (1819)
- Heracleum grossheimii Mandenova (1950)
- Heracleum lehmannianum Bunge
- Heracleum panaces Willd. ex Steven
- Heracleum sibiricum Sphalm
- Heracleum speciosum Weinm.
- Heracleum stevenii Manden.
- Heracleum tauricum Steven
- Heracleum villosum Fischer ex Sprengel (1818)
International Common Names
- English: cartwheel flower; giant cow parsnip; giant hogweed
- French: berce de Caucase; berce de Mantegazzi; berce géante
- Russian: boršcevik drevovidnyj; boršcevik Mantegacii; boršcevik sibirskij
Local Common Names
- Canada: giant cow parsnip
- Czech Republic: bolševník velkolepý
- Denmark: kæmpe-bjørneklo
- Finland: kæmpe-bjørneklo; kaukasianjattiputki
- Germany: Herkuleskraut; Herkulesstaude; Kaukasischer Bärenklau; Riesen-baerenklau
- Italy: Panace di Mantegazza; Panace gigante
- Netherlands: bereklauw, Perzische; Reuzenbereklauw
- Norway: kjempebjørnekjeks
- Poland: barszcz kaukaski; barszcz mantegazyjski; barszcz Mantegazziego
- Sweden: jättebjörnfloka; Kaukasisk jättefloka
- USA: cartwheel flower; giant cow parsnip
- HERMZ (Heracleum mantegazzianum)
Summary of InvasivenessTop of page
H. mantegazzianum has spread rapidly in a number of European countries after introduction as an ornamental from its native area in Russia and Georgia. It continues to be available as an ornamental, and also occurs as a contaminant of food produce in international trade, and is therefore likely to spread further. It is an undesirable invader on account of its large size, prolific seed production and vigorous growth leading to gross changes in vegetation, obstruction of access to river banks, soil erosion, and serious dermatological effects on skin contact. A large volume of information on this weed is incorporated into the volume by Pysek et al. (2007b).
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Plantae
- Phylum: Spermatophyta
- Subphylum: Angiospermae
- Class: Dicotyledonae
- Order: Apiales
- Family: Apiaceae
- Genus: Heracleum
- Species: Heracleum mantegazzianum
Notes on Taxonomy and NomenclatureTop of page
Other names used for Heracleum mantegazzianum in the British Isles (Tiley et al., 1996) have included H. asperum M. Bieb., H. caucasicum Steven, H. circassicum Manden., H. giganteum Fischer ex Hornem., H. grossheimii Manden., H. lehmannianum Bunge, H. panaces Willd. ex Steven, H. persicum Desf. ex Fischer, H. sibiricum Sphalm, H. speciosum Weinm., H. stevenii Manden., H. tauricum Steven, and H. villosum Fischer ex Sprengel, but it is understood that some of these (H. lehmannianum, H. persicum, and H. villosum) are treated as distinct species by at least some authorities (Satsyperova,1984; Jahodová, 2007a,b; Denness et al., 2013) and are not strictly synonyms. Jahodová et al. (2007a,b) reported AFLP studies which show H. persicum to be genetically distinct from H. mantegazzianum. Denness et al. (2013) showed distinct morphometric differences in the fruits of H. mantegazzianum and H. lehmannianum. Brummitt (1968) commented that the taxonomy and nomenclature of the naturalized plants from south-west Asia require further investigation. They are very variable in duration, height, shape, dissection and pubescence of the leaves and shape and size of fruit, and probably represent more than one species. Perennial plants with leaves pinnately divided into five segments may perhaps be referable to H. lehmannianum from central Asia. H. persicum is probably distinct and occasionally naturalized in Europe. See Similarities to Other Species for further comment on these and other species.
DescriptionTop of page
H. mantegazzianum is a monocarpic perennial herb, growing from a yellow, branched root system 40-60 cm deep and up to 15 cm across at the crown when mature. The root is somewhat contractile pulling the crown down to about 10 cm below the soil surface. While still vegetative, there is a rosette of leaves, increasing in size each year. These are alternate, the lowermost eventually up to 3 m long, to 1.7 m broad, ternately or pinnately lobed and coarsely toothed. Upper leaves on the flowering stem are progressively smaller. The upper leaf surface is glabrous but the underside and petiole are covered in bristles. When it finally flowers, usually after 3-5 years, there is a single hollow stem up to 2-5 m high and 10 cm in diameter. The stem is ridged, with purple blotches, and covered in pustulate bristles. The main inflorescence is a terminal compound umbel up to 80 cm across with about 100 unequal hairy rays, each 10-40 cm long. There are also up to eight satellite umbels which overtop the main one, and others developing on branches below. The main umbel is hermaphrodite; the lower ones, maturing earlier, may be only male. Flowers, on pedicels 10-20 mm long, are white or pinkish with petals up to 12 mm long. Numerous fruit flattened, elliptical, 6-18 mm long by 4-10 mm wide, narrowly winged, the larger fruits occurring on the main inflorescence and the smaller on satellites; glabrous to villous, splitting into two mericarps, each with 3-5 elongated oil ducts. For the first few years, the above-ground growth dies down each winter. Once it has flowered, the plant dies altogether (from Tiley et al., 1996.) Nielsen et al. (2005) have excellent line drawings of H. mantegazzianum and related species.
Plant TypeTop of page
DistributionTop of page
H. mantegazzianum is native to the southern slopes of the western Greater Caucasus in southern Russia and Georgia. Korovin et al. (1951) refer to its distribution as 'Caucasus: Ciscaucasus, W. Transcaucasus (N.)'. However, it is now becoming widely naturalised throughout northern Europe, with a continually increasing distribution. Pyšek et al. (1998), Collingham et al. (2000) and Nielsen et al. (2008) showed that winter temperatures are the best explanation factor for the species' distribution in Europe. It is also established and spreading in Canada, USA, Australia and New Zealand. Some of the spread into Russia could be natural but elsewhere the initial establishment is due to mainly deliberate introductions over the past 190 years.
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
|Country||Distribution||Last Reported||Origin||First Reported||Invasive||References||Notes|
|Georgia (Republic of)||Restricted distribution||Native||GRIN, 2002; EPPO, 2014|
|Iraq||Absent, no pest record||EPPO, 2014|
|Canada||Localised||Introduced||1944||Invasive||Page et al., 2006; Tiley et al., 1996; EPPO, 2014||Increasingly common in southwestern British Columbia and southern Ontario|
|-British Columbia||Present||EPPO, 2014; Morton, 1975; Dawe & White, 1979; Page et al., 2006|
|-New Brunswick||Present||Introduced||2000||Page et al., 2006|
|-Nova Scotia||Present||Introduced||1980||Page et al., 2006|
|-Ontario||Widespread||Introduced||1949||Invasive||Page et al., 2006|
|-Quebec||Present||Introduced||1990||Page et al., 2006|
|USA||Localised||Introduced||Invasive||USDA-NRCS, 2007; Tiley et al., 1996; EPPO, 2014|
|-District of Columbia||Restricted distribution||EPPO, 2014|
|-Florida||Restricted distribution||EPPO, 2014|
|-Indiana||Restricted distribution||EPPO, 2014|
|-Maine||Localised||Introduced||1981||Invasive||USDA-NRCS, 2007; EPPO, 2014|
|-Maryland||Restricted distribution||EPPO, 2014|
|-Massachusetts||Restricted distribution||EPPO, 2014|
|-Michigan||Localised||Introduced||1992||Invasive||USDA-NRCS, 2007; Case & Beaman, 1992; EPPO, 2014|
|-New York||Widespread||Introduced||1981||Invasive||USDA-NRCS, 2007; Berenbaum, 1981; PLANTS, 2002; EPPO, 2014|
|-North Carolina||Restricted distribution||EPPO, 2014|
|-Oregon||Restricted distribution||EPPO, 2014|
|-Pennsylvania||Localised||Introduced||Invasive||USDA-NRCS, 2007; EPPO, 2014|
|-Vermont||Localised||Introduced||Westbrooks, 1991; EPPO, 2014|
|-Washington||Widespread||Introduced||1953||Invasive||Morton, 1975; USDA-NRCS, 2007; EPPO, 2014|
|Austria||Restricted distribution||Introduced||Invasive||Tiley et al., 1996; Brummitt, 1968; EPPO, 2014|
|Belgium||Restricted distribution||Introduced||Invasive||Tiley et al., 1996; Brummitt, 1968; EPPO, 2014|
|Czech Republic||Widespread||Introduced||1862||Invasive||Pysek, 1994; Tiley et al., 1996; Pergl et al., 2012; EPPO, 2014|
|Denmark||Widespread||Introduced||Invasive||Tiley et al., 1996; Brummitt, 1968; EPPO, 2014|
|Estonia||Restricted distribution||EPPO, 2014||As HERMZ (Heracleum mantegazzianum)|
|Finland||Localised||Introduced||Invasive||Tiley et al., 1996; Brummitt, 1968; EPPO, 2014|
|France||Widespread||Introduced||Invasive||Tiley et al., 1996; Brummitt, 1968; EPPO, 2014|
|-Corsica||Absent, no pest record||EPPO, 2014|
|Germany||Widespread||Introduced||Invasive||Tiley et al., 1996; Brummitt, 1968; EPPO, 2014|
|Hungary||Localised||Introduced||1962||Invasive||Pysek, 1994; Tiley et al., 1996; Brummitt, 1968; EPPO, 2014|
|Iceland||Present||Introduced||Jahodová et al., 2007a|
|Ireland||Widespread||Introduced||1800s||Invasive||Tiley et al., 1996; Brummitt, 1968; EPPO, 2014|
|Italy||Localised||Introduced||Invasive||Tiley et al., 1996; Brummitt, 1968; EPPO, 2014|
|Latvia||Restricted distribution||Introduced||Fowler et al., 1991; Brummitt, 1968; EPPO, 2014|
|Liechtenstein||Localised||Introduced||Invasive||Tiley et al., 1996; Brummitt, 1968; EPPO, 2014|
|Netherlands||Localised||Introduced||Invasive||Tiley et al., 1996; Brummitt, 1968; EPPO, 2014|
|Norway||Widespread||Introduced||Invasive||Tiley et al., 1996; Brummitt, 1968; EPPO, 2014|
|Poland||Restricted distribution||EPPO, 2014|
|Russian Federation||Localised||Native||Korovin et al., 1951; EPPO, 2014|
|-Southern Russia||Restricted distribution||Native||Korovin et al., 1951; EPPO, 2014|
|Slovakia||Widespread||Introduced||Invasive||Tiley et al., 1996; EPPO, 2014|
|Sweden||Widespread||Introduced||1800s||Invasive||Lundstrom, 1984; Tiley et al., 1996; EPPO, 2014|
|Switzerland||Widespread||Introduced||Invasive||Tiley et al., 1996; Brummitt, 1968; EPPO, 2014|
|UK||Restricted distribution||Introduced||1817||Invasive||Tiley et al., 1996; Brummitt, 1968; EPPO, 2014|
|Australia||Localised||Introduced||Westbrooks, 1991; EPPO, 2014|
|-South Australia||Restricted distribution||EPPO, 2014|
|-Tasmania||Restricted distribution||EPPO, 2014|
|New Zealand||Present||Introduced||Weber, 2003|
History of Introduction and SpreadTop of page
H. mantegazzianum has been repeatedly introduced to other countries as a garden ornamental, often initially via botanic gardens, as is known for UK (Jahodová et al., 2007a). It was available as seed from Kew Botanic Gardens in 1817, presumably brought in from the Caucasus, and by 1828 was recorded as naturalised in Cambridgeshire. It was subsequently recorded in the Netherlands, Switzerland, Germany, Ireland, Denmark and, by 1862, in the Czech Republic. First records for other countries are indicated in the Distribution Table. Nielsen et al. (2005) produced a table showing the first records of H. mantegazzianum in the wild for 16 European countries, the latest being Slovakia and Iceland in about 1945. Whether it arrived directly from the Caucasus or via elsewhere in Europe is not generally known, but Jahodová et al. (2007a,b) suggested that it is likely that the current pattern of genetic diversity in Europe resulted from multiple introductions.
Spread following initial introduction is usually delayed, with a lag of 10-50 years being typical. Pysek et al. (2007d) indicated that it was first found in the wild in Czech Republic in 1877, 15 years after first introduction. Pysek and Prach (1993) and Pysek (1994), discussing the weed's spread in the Czech Republic, indicated that from 1862 up to about 1943, spread appeared to be exclusively due to cultivation as a garden ornamental but after that there was natural spread along the main rivers, and later along roadsides and railways. A genetic study from the western Swiss Alps (Henry et al., 2009) also reported anthropogenic as well as natural long-distance dispersal along rivers as main historical drivers of invasion. The role of the two mechanisms of spread appears to change with scale, with humans play a crucial role at the continental and regional scale and species traits at local level (Pyšek et al., 2008).
Risk of IntroductionTop of page
There is certainly risk of further spread – to further countries in Europe, and to further states in USA and Canada. This risk may be enhanced by some apparent adaptation of the weed to warmer climates, whereby it may need less cold winters for completion of the ‘stratification’ process to break dormancy (Jahodova et al., 2007a, quoting Krinke et al., 2005). Conversely, global warming could help to counteract this trend. Spread may occur by natural means (wind, water, etc) but also both accidentally and deliberately by human action. Although movement across borders is now restricted by quarantine regulations in many countries, there is still the temptation to import this very striking plant as an ornamental. It is freely available via internet mail-order.
HabitatTop of page
H. mantegazzianum in its native areas shows a wide ecological amplitude, occurring in a variety of habitats between 50 and 2000 m altitude, with annual rainfall between 1000 and 2000 mm per annum and a temperate, continental climate of hot summers and cold winters. At lower elevations it occurs as a constituent of nitrophilous tall-forb vegetation (Galio-Urticetae) in alluvial forests and old fields. At higher altitudes it grows in sub-alpine meadows and sub-alpine tall-forb vegetation (Mulgedio- Aconitetea) but is not dominant in these species-rich communities (Otte et al., 2007). In other areas, it has been commonly introduced to gardens as an ornamental and has spread from these foci to invade a variety of habitat types, especially along roadsides, river banks, railways, woodland fringes, graslands and arable fields, scrublands and ruderal sites such as rubbish dumps and waste ground. It is also increasingly found, in Germany and the Czech Republic, in abandoned grasslands and even at grasslands managed less intensively (Pyšek and Pyšek, 1995; Thiele and Otte, 2008;). In the Czech Republic, it has flourished in military areas. These sites are characterised by rich resource supply and disturbance but lack of regular or intensive management (Tiley et al., 1996; Thiele et al., 2007; Thiele and Otte, 2008). In Germany, the species dominates ruderal Arrhenatherion grasslands (endangered semi-natural grasslands) and Galio-Urticetea tall-forb stands (secondary successions from grasslands to woodlands after land abandonment). Maximum densities occur prevalently at young successional stages (Thiele and Otte, 2006). Invasion is discouraged by regular land use, shading by trees and low soil nutrients (Thiele et al., 2007). Pyšek et al. (2007d) showed that H. mantegazzianum changes its habitat preferences during the course of invasion.
Habitat ListTop of page
|Coastal areas||Secondary/tolerated habitat||Harmful (pest or invasive)|
|Disturbed areas||Principal habitat||Harmful (pest or invasive)|
|Managed grasslands (grazing systems)||Secondary/tolerated habitat||Harmful (pest or invasive)|
|Rail / roadsides||Principal habitat||Harmful (pest or invasive)|
|Urban / peri-urban areas||Principal habitat||Harmful (pest or invasive)|
|Natural forests||Secondary/tolerated habitat||Harmful (pest or invasive)|
|Natural grasslands||Secondary/tolerated habitat|
|Riverbanks||Secondary/tolerated habitat||Harmful (pest or invasive)|
|Scrub / shrublands||Secondary/tolerated habitat||Harmful (pest or invasive)|
|Wetlands||Secondary/tolerated habitat||Harmful (pest or invasive)|
Hosts/Species AffectedTop of page
H. mantegazzianum is not normally a weed of crops but there are reports of its encroachment into crop fields, such as potatoes in Sweden (Lundstrom, 1984). It has also been reported spreading into forest margins and sparse forest canopies (Thiele et al., 2007).
Biology and EcologyTop of page
The chromosome number is 2n = 22 (Tiley et al., 1996). This number is shared by most if not all Heracleum species. Hybridization is recorded with H. sphondyllium in the UK (Stace, 1991; Tiley et al., 1996), and in Germany (Ochsmann, 1996), H. sphondylium always being the female parent (Steward and Grace, 1984; Perglova et al., 2007), but this is relatively infrequent even where both species occur. The hybrids are virtually sterile.
Propagation is completely by seeds, which are produced in very large numbers, varying from 5000 to 100,000 per plant, on the flowers produced after 2-5 years, after which the plant dies (Perglová et al., 2007). Fruits comprise a pair of mericarps, which separate from each other before being shed and dispersed over a short distance (2-10 m) by wind. Longer-distance dispersal is achieved by water; seeds are reported to be able to float for 8 hours (Moravcová et al., 2007) or up to 3 days (Dawe and White, 1979). Seeds can also be spread by man (via vehicles or collecting the seed-heads for ornament).
The main umbel is hermaphrodite; the lower ones, maturing later, may be only male. Reproduction is amphimictic, the flowers being insect-pollinated and self compatible, though, within any umbel, all the anthers normally dehisce before the stigmas are receptive, ensuring out-crossing. There can, however, be some self-fertilization between primary and secondary or lower umbels (Perglová et al., 2006). Selfing can be seen as an advantage to an invasive species, allowing reproduction from widely isolated individuals. Flowers are visited by a wide range of insects, many of which are believed to be involved in pollination, including a number of Hymenoptera and Diptera and at least one Coleoptera (Tiley et al., 1996; Perglova et al., 2007). A detailed description of the phenology of flowering is provided by Otte and Franke (1998) and Perglova et al. (2006, 2007). In central Europe, elongation of the flowering stem begins in early June and first flowers open at the end of June. The terminal umbel flowers for about 10 days and fruits are mature after 44 days. Secondary, third, and fourth-order umbels flower successively later, but flowering finishes about the end of August as seed shed begins. Plant produce 20,000 seeds on average (Perglová et al., 2006).
Seeds when shed have an underdeveloped embryo and will not germinate in the autumn after shedding but require moist chilling, about 2 months below 8°C (stratification), over the winter to allow maturation of the embryo and breaking of dormancy (Moravcová et al., 2006, 2007). Germination can then occur, if slowly, at temperatures as low as 2°C (Moravcová et al., 2007). In practice this occurs in January to March in the UK. Drying tends to delay eventual germination or results in a requirement for additional or longer stratification. This may account for the association of the species with moist habitats. Inundation, however, can result in rotting of the seeds. Exposure to light is not apparently required for germination (Tiley et al., 1996).
Although seeds of H. mantegazzianum may remain viable for up to 15 years when stored dry (Lundström, 1989), their longevity in the field is normally much shorter. Moravcova et al. (2007) classify it has having a short-term persistent seed bank. They quote results of a trial in which over 90% of seeds germinated (or decayed) after the first winter, leaving 8.8% viable. This proportion declined to 2.7 and 1.2% in the following years. In one study no viable seeds were found after 7 years (Tiley et al., 1996).
Physiology and Phenology
After germination, a strong tap-root is formed which soon contracts to pull the crown downwards. The first true leaf develops about April, small and almost round, replaced in succession by steadily larger leaves, the fifth or sixth taking the adult form. Tiley et al. (1996) have detailed descriptions and drawings. The established vegetative plant has 3-4 leaves at any time.
The above-ground parts of the plant senesce and die down in late September/October (in the UK) and growth begins again from February/March (Tiley et al., 1996). Flowering occurs mainly in the third or fourth year of growth but may occur in the second year or be delayed to 5 or more years. This appears to depend on the size of the crown and reserves in the root system. Pergl et al. (2006) record some plants as old as 12 years. Plants destined to flower begin growth early, in January/February (Caffrey, 1999; Pergl et a., 2006), and have more erect leaves. Stem elongation is apparent in April/May in UK, in June in Czech Republic. The terminal bud, sheathed in bracts, appears in June and flowers are open from June to August, but mainly in July. Once the plant has flowered, it normally dies altogether. Detailed description of the phenology of flowering is provided by Perglova et al. (2007).
There are no marked differences in the phenology of H. mantegazzianum in native and invaded areas.
Climatic requirements include reasonable moisture with cold winters, with some degree of protection from prevailing winds. Cold winters are required to ensure germination, but may also be necessary for flowering. Although it is generally a plant of open ground, it can establish and grow successfully in open woodland, glade edges and partially shaded habitats. In secondary ranges, it invades nutrient-rich semi-natural grasslands, forest edges, riparian and anthropogenic (disturbed) habitats (Pyšek and Pyšek, 1995; Thiele al., 2007; Nielsen et al., 2008). However, it is also able to establish in nutrient-poor habitats such as peaty meadows or acidic soils in forest clearings (Pyšek et al., 2012). The weed needs moist conditions for much of the year, but can tolerate moderate summer droughts (Tiley et al., 1996). In its native Caucasus range it occupies large altitudinal gradient from 70 to 1950 m above sea level (Otte et al., 2007).
Although the weed tends to be associated with lowland sites in the UK, it was suggested by Willis and Hulme (2002) that this is mainly due to the sources of infestation being originally associated with gardens in the lowlands, and not due to a climatic limitation. In the Czech Republic, it rarely occurs in dry and warm lowlands (Pyšek et al., 2012). The seeds are shown to germinate at all elevations up to 600 m in north-east England.
Occurrence along river banks is usually associated with sandy or silty soils, but it is also recorded on a wide range of soil textures from gravels to clay. Highly organic or water-logged soils are also tolerated. It is usually found on alkaline or only slightly acid soils, from pH 6.0 upwards to 8.5, and appears to favour soils high in nitrogen (Pyšek and Pyšek, 1995). It is occasionally found close to the sea and apparently has some tolerance of salt spray.
ClimateTop of page
|Cs - Warm temperate climate with dry summer||Preferred||Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers|
|Cw - Warm temperate climate with dry winter||Tolerated||Warm temperate climate with dry winter (Warm average temp. > 10°C, Cold average temp. > 0°C, dry winters)|
|Ds - Continental climate with dry summer||Tolerated||Continental climate with dry summer (Warm average temp. > 10°C, coldest month < 0°C, dry summers)|
|Dw - Continental climate with dry winter||Tolerated||Continental climate with dry winter (Warm average temp. > 10°C, coldest month < 0°C, dry winters)|
Latitude/AltitudeTop of page
|Latitude North (°N)||Latitude South (°S)||Altitude Lower (m)||Altitude Upper (m)|
Air TemperatureTop of page
|Parameter||Lower limit||Upper limit|
|Absolute minimum temperature (ºC)||-17|
|Absolute minimum temperature (ºC)||-17||0|
|Mean annual temperature (ºC)||5||12|
|Mean maximum temperature of hottest month (ºC)||13||24|
|Mean minimum temperature of coldest month (ºC)||-6||5|
RainfallTop of page
|Parameter||Lower limit||Upper limit||Description|
|Dry season duration||0||7||number of consecutive months with <40 mm rainfall|
|Mean annual rainfall||500||2500||mm; lower/upper limits|
Soil TolerancesTop of page
- seasonally waterlogged
- seasonally waterlogged
- very alkaline
Special soil tolerances
Notes on Natural EnemiesTop of page
Hansen et al. (2006b, 2007) recorded 162 species of herbivore on H. mantegazzianum, though only 24 of the more genus- or family-specific species are tabulated. They include Coleoptera, gall-forming Diptera and leaf-mining Agromyzidae, sap-sucking Hemiptera, and stem-boring Lepidoptera. None recorded from the native range was specific to H. mantegazzianum. Hansen et al. (2006a) found two leaf-sucking aphids negatively influencing the plant growth and one stem-sucking aphid living in mutualistic relationship with ants and plant. In their review, Tiley et al. (1996) concluded that none of the organisms they listed caused consistently serious damage, though the damage to roots by the curculionid Liophloeus tesselatus has resulted in suggestions for its exploitation for biocontrol (Burki and Nentwig, 1998). However, Hattendorf et al. (2006) found that mature plants are quite tolerant to herbivory, and successful biological control could not thus be guaranteed. Research should instead be concentrated on earlier stages in the weed’s life cycle. Burki and Nentwig (1998) also listed 34 arthropod species associated with H. mantegazzianum in Switzerland. Berenbaum (1981) studied the insects attacking H. mantegazzianum and other members of Umbelliferae in New York State, USA, and noted that this species, together with H. lanatum, Pastinaca sativa and Angelica atropurpurea, were attacked by a narrower range of insects than other Umbellliferae. This was apparently due to the presence of angular furanocoumarins, which are more toxic than the more widely present linear furanocoumarins, and were not tolerated by the more generalist feeders. The significance of these defence substances is discussed in detail by Hattendorf et al. (2007).
Fowler et al. (1991) record only two fungal pathogens attacking H. mantegazzianum. Seier and Evans (2007) listed 12 species recorded before their own surveys for natural enemies in the native area of the Caucasus began in 2002 with the aim of identifying potential biological control agents (Seier et al., 2003; Seier and Evans, 2007). These revealed an extensive mycobiota associated with H. mantegazzianum, most species being new records for this host. They list 11 species on H. mantegazzianum in its native range and 24 in the invaded range, several occurring in both. Several pathogens were collected, belonging to the genera Ramulariopsis, Septoria, Phloeospora and Phoma, and three of these, including Phloeospora heraclei and Septoria heracleicola, were evaluated further (Seier et al., 2003; Seier and Evans, 2007). See Biological Control for further discussion.
Means of Movement and DispersalTop of page
Natural Dispersal (Non-Biotic)
Propagation is completely by seed, which are produced in very large numbers. Short-distance dispersal (2-10 m) is by wind, whereas longer-distance dispersal is achieved by water. The seeds are reported to float for 8 hours (Moravcová et al., 2007) or up to 3 days (Dawe and White, 1979). Several authors have shown the importance of long-distance dispersal in the species spread (Nehrbass et al. 2007; Pergl et al., 2011; Moenickes and Thiele, 2013).
Vector Transmission (Biotic)
Movement occurs by man, collecting the seed-heads for ornament and then disposing on rubbish heaps; also as a result of movement of soil in the course of building works, and by attachment to vehicles or in the slip-stream of road and rail vehicles.
Fowler (1998) notes that H. mantegazzianum is one of the three commonest proscribed species to be intercepted at entry points to USA, comprising 14% of all such interceptions. At least some of these instances are accidental, as in the accidental contamination of cumin seed (Westbrooks, 1991).
The interceptions recorded by Fowler (1998) are probably mainly deliberate introductions, such as for use as an ornamental. Such introduction is encouraged by the availability of seed from commercial nurseries via mail-order catalogues and from websites in, for example, Canada, the Netherlands and the UK.
Pathway VectorsTop of page
|Aircraft||Interception at ports of entry||Yes||Fowler, 1998; Westbrooks, 1991|
|Debris and waste associated with human activities||Yes|
|Land vehicles||Yes||Tiley et al., 1996|
|Luggage (incl. sailors’ sea chests)||Interception at ports of entry||Yes||Fowler, 1998; Westbrooks, 1991|
|Soil, sand, gravel etc.||Yes||Tiley et al., 1996|
|Water||Yes||Tiley et al., 1996|
|Wind||Yes||Tiley et al., 1996|
Plant TradeTop of page
|Plant parts liable to carry the pest in trade/transport||Pest stages||Borne internally||Borne externally||Visibility of pest or symptoms|
|Bark||larvae||Yes||Pest or symptoms not visible to the naked eye but usually visible under light microscope|
|Leaves||hyphae; nymphs; spores||Yes||Pest or symptoms not visible to the naked eye but usually visible under light microscope|
|Plant parts not known to carry the pest in trade/transport|
|Bulbs, Tubers, Corms, Rhizomes|
|Flowers, Inflorescences, Cones, Calyx|
|Fruits (inc. pods)|
|Growing medium accompanying plants|
|Seedlings, Micropropagated plants|
|Stems (above ground), Shoots, Trunks, Branches|
|True seeds (inc. grain)|
Economic ImpactTop of page
H. mantegazzianum is an alternative host of the carrot fly, Psila rosea, and of Sclerotinia sclerotiorum (Tiley et al., 1996). Lundstrom (1984) suggests that the presence of the weed may increase the risk of crops being affected by S. sclerotiorum but there are no records of direct impact on crops. There are, however, highly significant cost involved in measures taken to control the weed in amenity and other areas. Thiele and Otte (2007) quote estimates by Reinhardt et al. (2003) for annual costs in Germany amounting to over 12 million euro, including 1 million in health costs, 1.2 million in nature reserves, 2.1 million in road management, 2.4 million in municipal management and 5.6 million in district management.
Environmental ImpactTop of page
Impact on Habitats
Vanderhoeven et al. (2007) found increased concentrations of exchangeable essential nutrients under the canopy of exotic invasive plants, including H. mantegazzianum in Belgium, most strikingly in K and Mn (32% and 34% increase, respectively). Jandová et al. (2014) showed that longer invasion history increases soil conductivity, pH and extractable phosphorus, and decreased fungal/bacterial ratios. This result fits in well with previous reports of enhanced N dynamics in invaded sites, partly due to higher net primary productivity in exotic invasive plants compared to native vegetation. There are also reports of increased soil erosion resulting from the shading by H. mantegazzianum leading to suppression of grass and other low-growing plants, and bare soil exposed as the weed dies off in winter (Thiele and Otte, 2007). Wille et al. (2013) showed limited evidence for H. mantegazzianum having an allelopathic effect on the germination of native species.
Impact on Biodiversity
In amenity areas, established colonies compete strongly with, and rapidly replace, most other plants except trees (Williamson and Forbes, 1982). H. mantegazzianum tends to form monospecific stands with large standing biomass and extensive litter production. Its early germination allows it to develop populations well ahead of native species (Pyšek et al., 2007b). Nielsen et al. (2007) noted that the weed may change the composition and species diversity of indigenous plant communities, and in central Europe, investigations have shown a reduction in species richness and densities by up to 50-60% in areas that have been invaded (Hejda et al., 2009). However, in older H. mantegazzianum stands both population size and negative impact on biodiversity seem to be reduced (Nehrbass et al., 2006; Dostál et al., 2013). Dense monospecific stands reach the carrying capacity of the habitat and thus stagnate. In contrast, open stands and gaps created from disturbances are quickly filled by expanding population (Pergl et al., 2007).
Substantial programmes have been instituted in a number of European countries and EU Commission in order to control the weed, partly because of the human health hazards involved, but equally to reduce the possibility of environmental damage. Such programmes are described by Lundstrom (1984) in Sweden, Williamson and Forbes (1982) and Tiley and Philp (1992) in Scotland, and Caffrey and Madsen (2001) in Ireland. However, Thiele and Otte (2007) in a detailed analysis of the environmental effects of H. mantegazzianum
conclude that its effects are most pronounced in ruderal situations where the species it is displacing or influencing are themselves very common transient species, and where other dominant species such as Urtica dioica
may have a similar effect. In these situations its impact can be seen as a symptom of human-driven changes rather than a particular effect of the weed itself. The greatest danger is along river banks, where it can almost totally replace the natural vegetation and threaten biodiversity (Wade et al., 1997). In Sweden it can build up to a 'giant hogweed landscape' (Lundstrom, 1984).
Social ImpactTop of page
The bristly hairs on H. mantegazzianum contain furanocoumarins and any contact of skin with the plant can result in phyto-photodermatitis (Dennes et al., 2013; Mehta and Statham, 2007). Symptoms range from painful watery blisters, well illustrated by Nielsen et al. (2005), to full chemical burn (Chan et al., 2011). This occurs within 1-3 days on exposure to sunlight (Jakubska-Busse et al., 2013). Under cloudy conditions there may be no reaction. It may occasionally cause a recurrent dermatitis which can become a serious handicap (Williamson and Forbes, 1982; Klimaszyk et al., 2014). The compounds contained in seed essential oils may pose a risk to the eyes, skin and respiratory system (Jakubska-Busse et al., 2013). Large doses of furanocoumarins can cause cancer or fetus malformation (Nielsen et al., 2005). Immediately after exposure, the skin should be washed with soap and cold water to remove plant sap, and protected from sunlight until at least 48 hours post-exposure even if asymptomatic. Severe cases possibly require hospitalisation (Derraik, 2007). The health hazards of this species are one of the main reasons for concern over its spread. In tests on bacteria, Clarke (1975) showed that the sap of H. mantegazzianum could be mutagenic.
Dense infestations can lower the recreational value of the landscape and seriously interfere with access to amenity areas and river banks. Along roadsides, large stands can reduce visibility and result in a safety hazard.
Risk and Impact FactorsTop of page
- Causes allergic responses
- Competition - monopolizing resources
- Competition - shading
- Induces hypersensitivity
- Produces spines, thorns or burrs
- Rapid growth
- Ecosystem change/ habitat alteration
- Modification of successional patterns
- Negatively impacts animal health
- Negatively impacts human health
- Negatively impacts tourism
- Reduced amenity values
- Reduced native biodiversity
- Benefits from human association (i.e. it is a human commensal)
- Fast growing
- Has high reproductive potential
- Has propagules that can remain viable for more than one year
- Highly adaptable to different environments
- Highly mobile locally
- Long lived
- Pioneering in disturbed areas
- Proved invasive outside its native range
Likelihood of entry/control
- Highly likely to be transported internationally deliberately
- Highly likely to be transported internationally illegally
UsesTop of page
Buttenschøn and Nielsen (2007) commented that H. mantegazzianum has been widely grown as a forage plant in eastern Europe in the past. In invasive stands fresh weights of up to 94 t/ha have been measured and dry weights of 6-7 t/ha above ground and 2.4 t/ha below. However, its use has now declined due to problems of tainting of milk, and availability of alternatives.
Westbrooks (1991) reports that it is used as a spice in Iranian cooking.
H. mantegazzianum has been widely grown as an ornamental in Europe, thanks to its striking appearance and usefulness in flower arranging. It is still available via the Internet from commercial nurseries in Europe and North America.
A study in Hungary suggested that acetone extracts of H. mantegazzianum could have useful allelopathic effects on other weeds (Solymosi, 1994).
H. mantegazzianum has economic value to those who sell seed, but the growing plant has no consistent value that is not counter-balanced by its noxious characteristics.
Uses ListTop of page
Animal feed, fodder, forage
- Botanical garden/zoo
Similarities to Other Species/ConditionsTop of page
The commonest other Heracleum species in Europe, H. sphondylium, and the correspondingly common species in the USA, H. montanum Bartr. (= H. lanatum Michx.) are not readily confused with H. mantegazzianum, being much smaller, rarely over 2 m high, with grey-green, hairy, less acutely toothed leaves. More readily confused are some of the other more closely related species in Section Pubescentia, including H. persicum which is also smaller, rarely over 2 m, with stems violet, leaves more elongate, with 2-3 pairs of lateral leaf segments, and broad, short lobes, less deeply serrate. It is a true perennial, flowering more than once. This species is native to Turkey and Iran and naturalized locally in Scandinavia. H. sosnowskyi has a native range in the East Caucasus. It resembles H. mantegazzianum more closely in being monocarpic (flowering only once before dying) but is more densely hairy with umbel rays finely scabrous-hairy; it also has less dissected leaves and smaller petals on the marginate flowers. This was also grown as a forage crop in Russia and persists there and in countries bordering the southern and eastern Baltic. See Jahodova et al. (2007a) for discussion of relationships between the large Heracleum spp. Nielsen et al. (2005) have excellent line drawings, descriptions and colour plates of H. mantegazzianum and related species.
Prevention and ControlTop of page
H. mantegazzianum is already prohibited as a noxious weed in the USA (USDA-NRCS, 2002). In the UK, it is included in legislation requiring land owners to take steps to control it and prevent further spread (Willoughby, 1996). In the EU, a legislation on prevention and management of the introduction and spread of invasive alien species (COM (2013)620) is now prepared with H. mantegazzianum being a candidate for invasive alien species of the greatest EU concern.
Nielsen et al. (2005) provided a useful section on preventive measures, early detection and eradication, providing a checklist of actions, from the establishment of policies and guidelines, identification of routes of possible entry, identification of habitats most at risk, awareness campaigns, surveys of incidence and spread, eradication campaigns where necessary, followed up by monitoring. They note that mapping incidence and spread is made easy by the size and conspicuousness of the weed, ensuring that the public can provide reliable help, and even allowing clear monitoring from aerial photographs taken when the weed is in flower (Müllerová et al., 2005, 2013). Fonji et al. (2014) presented successful a project of public participation GIS involving school students monitoring H. mantegazzianum in Latvia.
Cultural Control and Sanitary Measures
H. mantegazzianum is not effectively controlled by light grazing, but intensive grazing, especially by sheep has provided good control and the rooting of pigs can also be highly effective (Tiley et al., 1996). Anderson and Calov (1996) reported on a 5-year study in Denmark in which the population of the weed was much reduced after 2 years of sheep grazing and completely eliminated after 5 years, when no viable seeds were found to remain in the soil. The weed may be slightly less palatable to cattle, but grazing by cattle as well as pigs is recommended in Ireland (Lucey, 1994).
Buttenschøn and Nielsen (2007) confirm that sheep and goats seek out young plants of H. mantegazzianum and recommend grazing to begin in mid-spring. Herds should preferably include individuals already familiar with the weed to reduce the risk of over-eating and poisoning. Dark-skinned, thick-pelted animals are less likely to suffer dermatitis. Nielsen et al. (2007) give more detail on the management of grazing for control of the weed.
Hand-pulling (with gloves) can be effective on young seedlings but is impractical on larger plants. Mechanical cutting is frequently used to clear river banks, but provides no long-term control, as there is rapid re-growth from below ground, and it may encourage the perennation of flowering shoots which would otherwise die after flowering. Cutting in May and June is somewhat more effective in reducing seed production and/or re-growth than cutting in March, but no single cutting can be relied on to prevent eventual seeding. Even four mowings per year for two years failed to kill the plant (Nielsen et al., 2007). There is a trade-off between early treatment with high regeneration and later umbel removal with more efficient reduction in fecundity, but with a necessity to handle more developed fruits that are able to ripen even on cut-off umbels (Pyšek et al., 2007c). Digging or ploughing to destroy the crown (below 10 cm soil depth), or otherwise severing the tap-root from the crown (‘root-cutting’) can completely kill the plant (Pyšek et al., 2007e).
Apart from the use of grazing animals, no other biological control method has yet been developed, though the possibilities have been discussed by Fowler et al. (1991); Fowler and Holden (1994); Burki and Nentwig (1998); and most recently by Cock and Seier (2007). The latter comment that there had been cause for optimism when the intensive ‘Giant Alien’ project was initiated in 2002, but after detailed appraisal of all the potential biocontrol agents listed by Hansen et al. (2007) and Seier and Evans (2007), they can only state that ‘there are still some areas that need clarification before concluding that there is no prospect of finding host-specific natural enemies for biological control of giant hogweed.’ All the most damaging insects and fungi have insufficiently narrow host range and can damage other Apiaceae such as parsnip (Pastinaca sativa L.).
In the UK, herbicides recommended for control of H. mantegazzianum include glyphosate, triclopyr and imazapyr but all must be applied early in the season (March to May) for best effect. Imazapyr has a residual effect in the soil that will prevent further germination but may also have a later effect on non-target species. Glyphosate is the most widely used compound, usually applied in April or May, when plants are 20-50 cm high, but owing to risks of toxicity to fish and algae, a buffer zone of 2 m should be left unsprayed adjacent to any river or other water body (Marcher, 2001). Nielsen et al. (2005; 2007) comment that the use of herbicides is increasingly controversial in parts of Europe, and there is a general (voluntary) ban on their use in public areas in Denmark. However, this ban was relaxed specially for the use of glyphosate on H. mantegazzianum. They do, however, suggest that herbicide should generally be regarded only as one of the first steps in an integrated control programme.
Tiley and Philp (1992) described an integrated two year programme of spraying with glyphosate in April/May, combined with cutting below ground when or where spraying is not feasible, and dealing with large plants threatening to flower before dealing with vegetative plants. Nielsen et al. (2007) discussed the various factors to be considered in arriving at an optimal integrated control system, such as the relative suitability of cutting, umbel removal, root cutting, chemical control and cultivation, according to the size and density of the infestation, and whether eradication or containment is the aim. They also presented a table showing the seasonal schedule for the different operations. Nielsen et al. (2005) produced a table showing the different range of options appropriate to small, medium and large populations of the weed and detailed estimates of the costs of each control method. They also emphasised the importance of re-vegetation as a component of any integrated management strategy. Ravn et al. (2007) discussed this in more detail, though their work mainly relates to H. sosnowskyi. Williamson and Forbes (1982) emphasised that due to the likely spread of seed down a river, it is important to ensure that upstream infestations are dealt with before attempting eradication further down. Müllerová et al. (2005) suggested targeted eradication towards new satellite dispersal foci and linear structures serving as invasion drivers. Deciding on an optimum control programme may be helped by the development of a ‘model-assisted evaluation of control strategies’ by Nehrbass and Winkler (2007), and risk maps predicting the species spread in the future (Cook et al., 2007; Nielsen et al., 2008; Thiele et al., 2008; Wallentin, 2013). Thiele et al. (2008) stated that although the models might not be precise enough for targeted eradication measures in heavily invaded landscapes, they may serve well to identify habitats prone to H. mantegazzianum invasion. Nielsen et al. (2005) finished with a section on ‘Planning a management programme’ with valuable suggestions for defining priorities. Remote sensing means were successfully applied for species monitoring and control to ensure early detection, targeted eradication and regular monitoring (Müllerová et al., 2005, 2013).
The value of re-vegetation following control programmes is discussed under IPM programmes.
Gaps in Knowledge/Research NeedsTop of page
Further study of potential biocontrol agents is required to clarify whether or not there is some chance of their successful use in control.
ReferencesTop of page
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ContributorsTop of page
30/04/2014 Updated by:
Jana Mullerova, Academy of Sciences of the Czech Republic, Czech Republic
30/09/2007 Updated by:
Chris Parker, Consultant, UK
Top of page
- = Present, no further details
- = Evidence of pathogen
- = Widespread
- = Last reported
- = Localised
- = Presence unconfirmed
- = Confined and subject to quarantine
- = See regional map for distribution within the country
- = Occasional or few reports