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 Add this item to the list   Heracleum mantegazzianum


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 Author(s):Sommier & Levier 
 Vernacular names:Giant hogweed (UK), reuzenberenklauw (NL) 
 Botanical thesaurus:
 Factsheet link (English):
 Factsheet link (French):
 Factsheet link (Dutch):


 Height of plant (m):2 - 5 
Roots and stem
 Description of subterranean parts:Taproot, yellow, branched, 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. 
 Description of stem:herbaceous, unbranched, ridged, with purple blotches, and covered in pustulate bristles. Plant sparsely hairy 
Fruit and seeds
 Description of fruit:flattened, elliptical, 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. 
 Description of propagule:seeds 
 Number of propagules per plant:5000 - 100000 
 Description of leaf:Ternately or pinnately lobed and coarsely toothed. Lowermost leaves the largest, upper leaves progressively smaller. The upper leaf surface is glabrous but the underside and petiole are also covered in bristles. 
alternate yes
opposite no
decussate no
whorled no
 Description of inflorescence:The main inflorescence is a terminal compound umbel up to 80 cm across with 30--150 unequal spreading-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. 
 Description of flower:pedicels 10-20 mm long 
Colour of flower:
white yes
yellow no
orange no
pink yes
brown no
red no
purple no
blue no
green no

Additional information

 Uses:H. mantegazzianum has been cultivated for silage in Russia and has been suggested as a forage crop in Poland. 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; also as a bee plant. 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). 
 Similar species:Heracleum sosnowskyi is generally smaller (1--3 m tall), more or less densely hairy, with smaller inflorescences (30--50 cm across and with 30--75 rays) and rays of umbels and umbellets finely scabrous-hairy. 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, including H. persicum which is also smaller, rarely over 2 m, and with leaves more divided with two pairs of lateral leaf segments, less deeply serrate. This species is apparently naturalized locally in the UK, Norway and possibly Finland. H. lehmannianum has leaves divided pinnately into five segments.(Hybridization is recorded with H. sphondyllium in the UK (Tiley et al., 1996), and in Germany (Ochsmann, 1996), but this is relatively infrequent even where both species occur, perhaps because of the lack of common insect visitors for pollination. The hybrids are virtually sterile.) 
 Look-alike link:

Distribution information

 Original distribution:Georgia, Russian Federation (S) (southern Russia and south-west Asia) 
 Current distribution:Austria, Belgium (1945), Czech Republic, Denmark, Estonia (1814 seedlist Tartu Univ bot garden; 1883 first record in herbarium), Finland, France, Germany, Hungary, Iceland, Ireland, Italy, Latvia (introduced in 1932), Liechtenstein, Netherlands, Norway, Poland, Slovakia, Sweden, Switzerland, United Kingdom (1817 Kew seedlist; 1828 first record natural population), Canada, USA, Australia, New Zealand 
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Biochemistry and molecular data

 Ploidy:2n = 22 (Tiley et al., 1996). This number is shared by most if not all Heracleum species. 


Life cycle:
annual no
perennial no
monocarp no
biennial no
 Competitiveness:H. mantegazzianum competes with natural vegetation, reducing grass and other low-growing plants. In amenity areas, established colonies compete strongly with, and rapidly replace most other plants except trees (Williamson and Forbes, 1982). Along river banks, it can almost totally replace the natural vegetation and threaten biodiversity. In Sweden it can build up to a giant hogweed landscape (Lundstrom, 1984). It has not been documented as a problem in national parks but has the capacity to be so. 
Flowering time in Europe:
January no
February no
March no
April no
May no
June variable
July yes
August variable
September no
October no
November no
December no
 Pollination characteristics:Insect-pollinated and self compatible; anthers normally dehisce before the stigmas are receptive, ensuring out-crossing. There can, however, be some self-fertilization between primary and secondary umbels. 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). 
 Dormancy:Seeds will not germinate in the autumn after shedding but require moist chilling (stratification) over the winter to break dormancy. Germination then 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). Seeds may remain viable for up to 15 years when stored dry but in the field this period is apparently much shorter and in one study no viable seeds were found after 7 years (Tiley et al., 1996). 
 Habitat requirements:H. mantegazzianum in its native areas is a plant of forest edges and glades, often along stream-sides, in montane areas with annual rainfall between 1000 and 2000 mm per annum and a temperate, continental climate of hot summers and cold winters. 
 Ecological amplitude:Climatic amplitude (estimates)- Mean annual rainfall: 500 - 2500 mm- Rainfall regime: uniform- Dry season duration: 0 - 7 months- Mean annual temperature: 5 - 12ºC- Mean maximum temperature of hottest month: 13 - 24ºC- Mean minimum temperature of coldest month: -6 - 5ºC- Absolute minimum temperature: -17 - 0ºCSoil descriptors- Soil texture: light; medium; heavy- Soil drainage: free; impeded; seasonally waterlogged- Soil reaction: neutral; alkaline- Special soil tolerances: shallow 
 Habitat elsewhere:In other areas, it has been commonly introduced to gardens as an ornamental and has spread from these foci, especially along river courses, roads and railways to invade river banks, damp places, rubbish dumps and waste ground (Tiley et al., 1996). Weed in natural forests, rail / roadsides, coastal areas, urban areas, managed grasslands, wetlands. 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 woodland, glade edges and partially shaded habitats. The weed needs moist conditions for much of the year, but can tolerate moderate summer droughts (Tiley et al., 1996). Although the weed tends to be associated with lowland sites in the UK, it is 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. 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. Pysek and Pysek (1995) state that it does not occur on acidic soils in the Czech Republic, but does appear to be favoured by soils high in nitrogen. It is occasionally found close to the sea and apparently has some tolerance of salt spray. 

Invasiveness, risk and control

Dispersal mechanism:
wind yes
water yes
others yes
endozoochorous no
ectozoochorous no

Link to other websites / databases

 Link to other websites_Url: