Heracleum mantegazzianum, Heracleum sosnowskyi and Heracleum persicum
2009; Wiley; Volume: 39; Issue: 3 Linguagem: Inglês
10.1111/j.1365-2338.2009.02313.x
ISSN1365-2338
Tópico(s)Botany, Ecology, and Taxonomy Studies
ResumoEPPO BulletinVolume 39, Issue 3 p. 489-499 Free Access Heracleum mantegazzianum, Heracleum sosnowskyi and Heracleum persicum First published: 27 November 2009 https://doi.org/10.1111/j.1365-2338.2009.02313.xCitations: 17AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Identity of Heracleum mantegazzianum Scientific name: Heracleum mantegazzianum Sommier & Levier Synonyms: Heracleum circassicum Mandenova, Heracleum grossheimii Mandenova, Heracleum giganteum Hornemann. Taxonomic position: Apiaceae. Common names: giant hogweed, giant cow parsnip, cartwheel flower (English), kæmpe-bjørneklo (Danish), berce du caucase, berce de Mantegazzi (French), Herkulesstaude, Riesenbärenklau, kaukasischer Bärenklau (German), kaukasianjättiputki (Finnish), kjempebjønnkjeks (Norwegian), barszcz mantegazyjski (Polish), kaukasisk jättefloka (Swedish), hiid-karuputk (Estonian), tröllahvönn, bjarnarkló (Icelandic), mantegaca latvnis (Latvian), mantegaco barštis (Lithuanian), reuzenberenklauw (Dutch) (Klingenstein, 2006), bolševník velkolepý (Czech). EPPO code: HERMZ. Notes on taxonomy and nomenclature Nomenclature is difficult due to unclear taxonomy. Heracleum mantegazzianum and related tall Heracleum spp. originate from the Caucasus region (one of two centres of diversity for Heracleum spp., the other being China), and synonymy therefore depends on botanical explorations in that region. The main sources of synonymy are: (i) historical – before the taxonomic description of a full range of Heracleum spp., plants were referred to as those described first (beginning of the 19th century); (ii) modern – due to intensive taxonomic work by Russian botanists (in the 20th century), who generally accept a narrower species concept. Historical synonyms include: Heracleum speciosum Weinmann, Spondylium pubescens Hoffmann and Pastinaca pubescens (Hoffmann) Calestani. These were early names that are no longer in taxonomic use and cannot be regarded as true synonyms. Heracleum pubescens (Hoffmann) Marschall von Bieberstein (now considered an endemic of Crimea, Ukraine) was the first tall Heracleum sp. to be described (in 1819), and many plants were later referred to as this species. Modern synonyms are quoted above (see ‘synonyms’). Other historical synonyms include Heracleum asperum Marschall von Bieberstein, Heracleum caucasicum Steven, Heracleum lehmannianum Bunge, Heracleum panaces Steven, Heracleum stevenii Mandenova, Heracleum tauricum Steven and Heracleum villosum Sprengel. The names of two other species now naturalized in Europe (Heracleum persicum Fischer and H. sosnowskyi Mandenova) are also historical synonyms of H. mantegazzianum. The name Heracleum trachyloma Fischer & C.A. Meyer has recently been used for the most widespread Heracleum sp. naturalized in the UK (Sell & Murrell, 2009). Phytosanitary categorization: EPPO List of invasive alien plants. Identity of Heracleum sosnowskyi Scientific name: Heracleum sosnowskyi Mandenova Taxonomic position: Apiaceae. Common names: Sosnowskyi’s hogweed (English), бopщeвик Cocнoвcкoгo (Russian), sosnovska latvānis (Latvian), sosnovskio barštis (Lithuanian), sosnovski karuputk (Estonian), barszcz Sosnowskiego (Polish), Sosnowsky’s Bärenklau (German), bolševník Sosnowského (Czech). EPPO code: HERSO. Notes on taxonomy and nomenclature Heracleum sosnowskyi was only described in 1944, so, until then, plants of this species were recorded as some of the previously described Heracleum spp. These include H. pubescens (described in 1819 from Crimea and Eastern Greater Caucasus, now considered as endemic of Crimea, Ukraine), H. wilhelmsii (described in 1841 from Georgia) or H. mantegazzianum (described in 1895 from Western Greater Caucasus) (Jahodováet al., 2007). The plants naturalized in the Western European countries have generally been known as H. mantegazzianum, without consideration of the possibility that H. sosnowskyi or another invasive Heracleum sp. (e.g. H. persicum Fischer) might also be present. Phytosanitary categorization: EPPO A2 list of pests recommended for regulation. Identity of Heracleum persicum Scientific name: Heracleum persicum Fischer Synonyms: Heracleum laciniatum auct. scand., non Hornem, H. tromsoensis, H. Cf. pubescens Marschall von Bieberstein. Taxonomic position: Apiaceae. Common names: persischer Bärenklau (German), perzische bereklauw (Dutch), Tromsøpalme (Norwegian), persianjättiputki (Finnish). EPPO code: HERPO. Notes on taxonomy and nomenclature This plant was described in 1829 and some of the subsequent identifications of the plant as Heracleum persicum were probably mistaken with H. mantegazzianum and H. sosnowskyi (Nielsen et al., 2005). In Norwegian, Danish and Swedish floras, the plant has been called H. laciniatum, but recent morphological and genetic analyses have shown that it is synonymous with H. persicum (Jahodováet al., 2007; Lars Fröberg, unpublished data). Phytosanitary categorization: EPPO A2 list of pests recommended for regulation. Geographical distribution of Heracleum mantegazzianum EPPO region: Austria, Belgium, Czech Republic, Denmark, Estonia, Finland, France, Georgia (native), Germany, Hungary, Iceland, Ireland, Italy, Liechtenstein, Netherlands, Norway, Poland, Russia (Southern Russia) (native), Slovakia, Sweden, Switzerland, United Kingdom. Asia: Georgia (native). North America: Canada (British Columbia, Ontario, Newfoundland), USA (Connecticut, Illinois, Indiana, Maine, Maryland, Massachusetts, Michigan, New York, Oregon, Pennsylvania, Vermont, Washington). Oceania: Australia, New Zealand. Note: the plant is listed as a noxious weed not occurring in North Carolina and Florida. History of introduction and spread Heracleum mantegazzianum is native to the Western Greater Caucasus (Russia, Georgia). It is now becoming widely naturalized throughout Western Europe with a continuing increase in its distribution. It is considered invasive in most of the countries where it has repeatedly been introduced as a garden ornamental from the 1800s, after which there has been natural spread along rivers. The first known record in Europe came from the Royal Botanic Garden, Kew (UK) in 1817. Details on the spread of H. mantegazzianum across Europe are summarized by Jahodováet al. (2007). It was introduced as early as 1917 into North America as a garden curiosity. In Canada, the first record of H. mantegazzianum comes from a herbarium specimen collected in Ontario in 1949, although it may have been present in British Columbia in the 1920s or 1930s. Further spread has recently been observed in the USA, with new state records from Vermont in 2002, Maryland and Michigan in 2003 and Indiana in 2004 (NAPIS, 2004). In the Czech Republic, a front of populations of H. mantegazzianum has been observed advancing at an average rate of about 10 m per year, the total area increasing by some 1200 m2 each year. The number of host localities has doubled every 14 years during the phase of rapid invasion (Pyšek et al., 2007). Geographical distribution of Heracleum sosnowskyi EPPO region: Armenia (native), Azerbaijan, Belarus, Estonia, Georgia (native), Germany, Hungary, Latvia, Lithuania, Poland, Russia (Karachay-Cherkessia, Kabardino-Balkaria, North Ossetia, Ingushetia, Chechnya, Dagestan and possibly Black Sea coast) (native) Central and Northern Russia (introduced), Turkey (introduced), Ukraine (introduced). History of introduction and spread Heracleum sosnowskyi is native to the Eastern and Central Caucasus (first described from Georgia), Central, Eastern and South-Western Transcaucasia and N.E. Anatolia in Turkey. It was introduced into North-West Russia at the end of the 1940s, for evaluation in experimental farms as a potential forage crop. From the 1960s, it was cultivated for forage over wider areas in Russia, Belarus, Ukraine and the Baltic States. It was also tested in the former German Democratic Republic, Hungary and Poland. Heracleum sosnowskyi started to spread very rapidly at the end of the 1980s as agricultural production systems and markets changed. In Russia, H. sosnowskyi has been hybridized in breeding programmes, with various other Heracleum spp. from different parts of the former USSR. Such hybrids may also have been naturalized. In 2008, the Latvian NPPO detected 7956 ha of territories invaded by H. sosnowskyi. Geographical distribution of Heracleum persicum EPPO region: Denmark, Finland, Norway, Sweden. Asia (native): Iran, Iraq, Turkey. Note: Possible occurrence in Hungary and in the UK. History of introduction and spread The earliest record for introduction originates from the seed list at the Royal Botanic Garden, Kew (UK), where the plant was received in 1819. Seeds from London populations of a similar plant were taken by English horticulturalists and planted in northern Norway as early as 1836 (Nielsen et al., 2005). The species may have been sent to botanical gardens around Europe, but surprisingly, naturalized populations are only reported from Scandinavia, principally from Norway. Heracleum persicum is known as the Tromsøpalm as it is the most common of the Heracleum sp. in Northern Norway. Heracleum persicum is in a stage of rapid expansion in the North and East of Norway especially in the region around Trondheim (Fremstad & Elven, 2006; Fremstad, 2007). In Finland, H. persicum is established but rare in the South of Finland and found occasionally in the North. Heracleum persicum has been established in Northern Sweden since the 1940s with seeds originating from Norway. It is found locally in Northern Sweden around settlements and towns (Often & Ericssonn, 1996). Morphology Plant type Heracleum mantegazzianum and H. sosnowskyi are herbaceous, monocarpic, perennial, seed-propagated plants (Tkachenko, 1989). Heracleum persicum is a herbaceous, polycarpic (flowering several times) perennial seed-propagated plant. Description of Heracleum mantegazzianum Heracleum mantegazzianum grows from a yellow branched root system 40–60 cm deep, which reaches 15 cm in diameter at the crown when mature. The species persists in the form of a vegetative rosette for several years, and then flowers (after the plant has accumulated enough resources for reproduction). Perglováet al. (2007) report that H. mantegazzianum is strictly monocarpic and dies after flowering, but there are some reports of polycarpy. The flowering stem can reach 5 m in height and 10 cm in diameter at the base. The stem is ridged, with purple blotches, and covered with pustulate bristles. Leaves are alternate, up to 3 m long and 1.7 m wide, ternately or pinnately lobed and coarsely toothed; upper leaves are progressively smaller, with the upper leaf surface glabrous and the underside pubescent, as is the petiole. The inflorescences are compound umbels of four orders. The main inflorescence (first-order) is a terminal compound umbel up to 80 cm in diameter with about 100 unequal hairy rays, each 10–40 cm long. There are also up to 8 satellite umbels which usually overtop the main one, and others developing on branches below. The main umbel is hermaphrodite; the umbels of higher orders, maturing later, may be only male. Flowers, on pedicels 10–20 mm long are white or pinkish with petals up to 12 mm long. Fruits are flattened and elliptical; 6–18 mm long by 4–10 mm wide; narrowly winged; with the larger fruits occurring on the main inflorescence and the smaller on satellites and branches, glabrous to villous; splitting into two mericarps; each with 3–5 elongated oil canals. Description of Heracleum sosnowskyi Heracleum sosnowskyi is closely related to H. mantegazzianum and can easily be confused with it. Plants have a thick taproot and are usually smaller than those of H. mantegazzianum since they are up to 3 m tall instead of 5 (Nielsen et al., 2005). Heracleum sosnowskyi is distinguishable by having less divided leaves, the leaves of mature plants being divided to a varying extent, either into three approximately equal parts, which may themselves be similarly divided, or into more than three leaflets arranged in rows along the central rachis (pinnate). Outer petals are radiate, 9–10 mm long, while those of H. mantegazzianum are 12 mm long. The fine hirsute indumentum of the rays of the umbel is also characteristic of this species. Each compound umbel has 30–150 rays (Nielsen et al., 2005) and only short hairs. Fruits are oval to elliptical, broadly winged and comprise a pair of mericarps, which separate from each other before being shed, each containing a seed. Fruits from the terminal umbels tend to be smaller: some 10.5–16.5 mm long and 5.3–8.7 mm wide (Moravcováet al., 2007). Mature fruits are brown with swollen brown oil canals ¾ of the length of the fruits. This is a distinctive character of the species. Description of Heracleum persicum Heracleum persicum is closely related to H. mantegazzianum and can easily be confused with it. Plants are most often 1–2 m in height, especially for newly established plants, but can reach 3–4 m. Each plant often has more that one stem. Each stem is purple, 1.5 to 2 cm thick, with large even areas of purple to purple-red colour at the base. Leaves are more divided than for H. mantegazzianum. They may be up to 2 m in length and deeply incised with very sharp points, with 2–3 pairs of lateral leaf segments and less deeply serrate. The whole plant smells of aniseed. Umbels of H. persicum are more convex than those of H. mantegazzianum, which has flat umbels. Whereas H. mantegazzianum has especially large umbels with side umbels as well developed as the main umbel, and all umbels develop fruit, the side umbels of H. persicum are rather small compared with the main umbel and often do not develop fruit. According to Lars Fröberg (Fremstad & Elven, 2006), another characteristic which may be used in distinguishing the two species is the shape and placement of hairs on the two plants. Heracleum mantegazzianum has transparent, very curly hairs which stand out at 45 degrees from the stem. Heracleum persicum has somewhat stiffer and whiter hairs, which stand straight out from the stem. (1) [ Drawings of H. mantegazzianum, H. sosnowskyi and H. persicum seeds by J. C. Schou (in Nielsen et al., 2005). ] The morphological characteristics of H. persicum vary according to the environmental conditions in which it grows, which makes identification difficult. Similarities to other species Heracleum spp. hybridize easily, thus causing confusion in identification. The common Heracleum spp. in Europe, H. sphondylium, H. sibiricum and the correspondingly common species in the USA, H. montanum Bartr. (= H. lanatum Michx.) are not easily confused with H. mantegazzianum, being much smaller, rarely over 2 m high, with grey-green, pubescent and less acutely toothed leaves. Biology and ecology Heracleum mantegazzianum Seeds germinate in early spring after dormancy is broken by the cold and wet conditions of autumn and winter, by temperatures within the range of 1–6°C (Moravcováet al., 2007). Germination then occurs from January to March in the United Kingdom. Drying tends to delay eventual germination or results in a requirement for additional or longer stratification. Exposure to light is apparently not required for germination. After germination, a strong tap-root is formed which soon contracts to pull the crown downwards. In the Czech Republic, the first leaves of the rosette are usually visible at the end of February or in March (they often start growth under the snow cover). Stem elongation is apparent at the end of May and the peak of flowering occurs at the end of June and beginning of July. The first true leaf develops in April, small and almost round, replaced in succession by steadily larger leaves, the fifth or sixth taking the adult form. The established vegetative plant has 3–4 functional leaves at any time. Flowering occurs mainly in the third year of growth but under unfavourable conditions such as grazing, cutting or nutrient deficiency, flowering is postponed until sufficient reserves have been accumulated. In pastures, flowering may be delayed up to 7 years, which appears to be driven by the size of the crown and reserves in the root system. Individuals 12 years old have been reported from extremely dry sites (Pergl et al., 2006). The flowers of H. mantegazzianum are insect-pollinated and self-compatible (Perglováet al., 2007). Self-pollination has been identified as advantageous in some colonizing species (Rejmánek et al., 2005) and may lead to accelerated spread (Daehler, 1998). Heracleum mantegazzianum has unspecialized flowers which are pollinated by unspecialized insects; Coleoptera, Diptera, Hemiptera and Hymenoptera are the most frequent visitors (Grace & Nelson, 1981). Most fruits ripen in the second half of July and start to be released (Perglováet al., 2007). Propagation is exclusively by seeds, which are produced in very large numbers. Some 10 000 to 20 000 fruits are produced per plant in Europe, the maximum reaching some 50 000 fruits (Perglováet al., 2007). Each mericarp contains one seed (Moravcováet al., 2007). Seeds may remain viable for up to 15 years when stored dry, but in the field this period is apparently much shorter – only 8.8% of seeds buried in the soil survived 1 year, 2.7% lasted 2 years and 1.2% remained viable and dormant after 3 years (Moravcováet al., 2007). Correspondingly, no viable seeds were found in a Heracleum site after 7 years of sheep grazing (Andersen & Calov, 1996). The vertical distribution of seeds in the soil seed bank shows that 94% of the total seeds, including dead seeds, are in the upper 0.5 cm of the soil layer, with few in the deeper layers of 6–10 cm and 11–15 cm (Moravcováet al., 2007). In the United Kingdom, the above ground parts of the vegetative plants senesce and die back in late September/October. The chromosome number of H. mantegazzianum is 2n = 22, as in most, if not all Heracleum sp. Hybridization is recorded with H. sphondyllium in Germany and the United Kingdom (Ochsmann, 1996; Tiley et al., 1996), but this is relatively infrequent even where the two species occur together, perhaps because of the lack of common insect visitors for pollination. The hybrids are virtually sterile. Heracleum sosnowskyi Seeds germinate in early spring after morphophysiological dormancy is broken by the cold and wet conditions of autumn and winter. Autumn germination under favourable conditions may also be possible (though not observed), as seeds of H. sosnowskyi require a shorter period of cold stratification to break dormancy (2 months or less) than those of H. mantegazzianum (Moravcováet al., 2007). Experiments in the Czech Republic have shown that the seed bank is very quickly depleted by rapid germination in spring and seeds do not survive for more than one season. However, experiments in regions where H. sosnowskyi is invasive are needed to verify this. Germination of H. sosnowskyi seeds under laboratory conditions is very high (71–94% in different temperature regimes) (Moravcováet al., 2007). Flowering occurs from June to August. As with H. mantegazzianum, the flowers of H. sosnowskyi are insect pollinated, visited by a wide range of insects, including a number of Hymenoptera, Diptera and Coleoptera. The plant is reported to live up to 6 years when planted for biomass and silage production (Satsyperova, 1984). Propagation is exclusively by seeds. An average plant of H. sosnowskyi is reported to have produced 8836 fruits in the Leningrad area, Russia (Tkachenko, 1989). The majority of seeds (98.2%) are distributed in the upper soil layer of 0–5 cm, with little in the deeper layers of 6–10 cm and 11–15 cm (Moravcováet al., 2007). Seeds are dispersed locally near the parent plants over longer distances by watercourses. When the plant is established, its huge size, fast growth and voluminous green mass suppress companion plant species, so that it forms a single-species stand. Heracleum persicum The plant has a growth and development similar to those of H. mantegazzianum. Pollination by insects is common, but self-pollination also occurs. The species is spread by seeds and does not reproduce vegetatively. Because the side umbels of the plant are often poorly developed and do not always produce ripe fruits, the potential of H. persicum for seed production is thought to be inferior to that of H. mantegazzianum. The leaves of H. persicum wilt in the autumn, but the plant over winters with buds below the soil surface. Nutrients are stored in the root system and the size and development of the root system determine the time for flowering. The plant needs one or more years to build up a nutrient reserve in its root system to be able to flower. Habitat Heracleum mantegazzianum in its native range is a plant of forest edges and glades, often alongside streams, in mountain areas with annual rainfall of 1000–2000 mm, characterized by temperate, continental climates of hot summers and cold winters. The species is a good colonizer of open and bare ground, and benefits from man-induced habitat disturbances (i.e. a pioneer species). Both in the native and introduced range it can be found forming dense populations in man-made stands. In the introduced range, a high proportion of stands include rivers, roads, railway banks, damp places, rubbish dumps and waste ground (Pyšek & Prach, 1993; Pyšek & Pyšek, 1995; Tiley et al., 1996). In addition to rural habitats, the plant occurs in urban areas, gardens and parks (Pyšek & Pyšek, 1995). Although it is generally a plant of open ground, it can establish and grow successfully in woodland, the edges of clearings, and partially shaded habitats. According to a German study (Thiele et al., 2007), the most common habitat types are linear structures along traffic routes (roadsides, railway margins) and flowing waters. These habitats can be completely open or partly shaded by tree lines, single trees or shrubs. Heracleum mantegazzianum can often be found at fringes and margins of woodlands and grasslands. In terms of area covered by stands of H. mantegazzianum, abandoned grasslands are the most represented habitat types, followed by tall-herb stands which can be found at long-abandoned former grassland sites or at other disused sites. Ruderal places (i. e. site that recently have been severely disturbed by human activities) are suitable habitats (e. g. sand pit, building sites, rubbish dumps). Managed grasslands are marginal habitats, as the plant is not invasive as long as regular management is applied. Moreover, Thiele et al. (2007) found out according to their study in Germany that sites invaded by H. mantegazzianum are not subject to regular land use except for marginal occurrences in managed grasslands. Indeed, 71% of plots examined were disused, 17% were maintained by rather irregular mowing or removal of shrubs and trees, and only 12% of sites were under agricultural land use. The native range of H. sosnowskyi is in the Caucasus where it grows in mountain areas alongside streams, in forests or in alpine meadows. The climate in the natural habitat is continental, with hot summers and cold winters. In other areas, H. sosnowskyi has been introduced as an agricultural crop and has spread rapidly, infesting grasslands, forests, wetlands, riverbanks/canal sides, rail/roadsides, urban areas, as well as abandoned agricultural land, particularly in Latvia (Thiele et al., 2007). Heracleum persicum colonizes the same habitats as H. mantegazzianum: cultural landscapes, areas strongly influenced by anthropogenic factors, urban areas (along roadsides and railroads), grasslands and wetlands (Klingenstein, 2006). It is common in meadows, pasturelands or agricultural fields that are no longer in use and in ruderal areas or wastelands, as well as in riparian habitats, growing along streams and rivers. It has been reported growing on mountainsides and on mountain slopes and in cracks where the soil layer is quite thin, but it is not known whether it will flower in this habitat. It has also been found in coastal habitats (beaches) where H. mantegazzianum has not been found. In Tromsø, H. persicum has been found growing among the seaweed vegetation on beaches. Its presence on unpopulated islands indicates that it may be spread with sea water (Alm, 1988; Alm & Jensen, 1993). In Norway it is becoming more common growing at the edge of forests and has been reported as growing in the birch forest (Betula spp.) probably because of the high light conditions of this ecosystem (Fremstad & Elven, 2006). It does not flower in the forest, but survives for a long time in the shade under the trees. Environmental requirements Climatic preferences include temperate (no dry season), and cold (no dry season) climatic regions, with reasonable moisture and cold winters. Cold winters are required to ensure germination. Moist conditions are favoured for much of the year, but moderate summer droughts can be tolerated (Tiley et al., 1996). Heracleum mantegazzianum tends to be associated with lowland sites in the United Kingdom, mainly due to the sources of infestation being originally associated with gardens in the lowlands, and not due to a climatic limitation (Willis & Hulme, 2002). The seeds are shown to germinate at all elevations up to 600 m in North-East England. In the Czech Republic the plants occur in a wide range of altitudes from 154 to 1249 m. In the native distribution range it grows in the altitudes up to 2200 m (Otte & Thiele, 2007). A study by Thiele et al. (2007) in Germany showed that H. mantegazzianum needs fairly high nutrient rich soils and moisture levels for optimal growth. With respect to pH values, H. mantegazzianum was found in a wide range of conditions from acidic to alkaline. Extreme values were 4.0 and 8.5. In its native distribution range, it was found growing on soils of pH ranging from 5.34 to 6.68 (Pergl et al., unpublished data). Occurrence along riverbanks is usually associated with sandy or silty soils, but a wide range of soil textures are also tolerated from gravels to clay and highly organic or waterlogged soils. It is occasionally found close to the sea and apparently has some tolerance of salt spray. Growth of the species in semi-shade is fairly good, but it cannot grow in full shade (Thiele et al., 2007). Heracleum sosnowskyi develops in fresh and slightly moist, neutral soils, rich in nutrients, in the pH range 6.3–7.0. Heracleum sosnowskyi communities have developed in artificial and seminatural habitats over the last 20 years. They are nitrophilous and their expansion is stimulated by eutrophication of the environment (Laivins & Gavrilova, 2003). Heracleum sosnowskyi is a light demanding plant which cannot tolerate shade in the first growth stages (Oboļeviča, 2001). Nevertheless, it is considered more shade-tolerant than H. mantegazzianum (Nielsen et al., 2005). Climatic and vegetational categorization Heracleum mantegazzianum is associated with areas with warm to hot summers and cool winters. It is not favoured by drier conditions. Hardiness is not specified, but the plant is probably hardy to zone 6 (−23 to −18°C). It is associated with the vegetation zones: temperate deciduous forests and mixed conifer forests. A study of climatic effects on H. mantegazzianum in its invaded range in the Czech Republic conducted by Pyšek et al. (1998) showed that the distribution of the species was significantly affected by January isotherm; the species was less represented in areas with warmer January isotherm. Heracleum sosnowskyi, like H. mantegazzianum, is associated with areas with warm to hot wet summers and cool wet winters. It is considered to be more suited to continental climates and is not adapted to drier conditions. It is winter hardy down to −25°C. The new shoots of H. sosnowskyi are rather cold-resistant and can survive −4 to −7°C. It is found that starting from the second year, they can survive up to −25°C, and under a snow cover, even down to −45°C (Oboļeviča, 2001). Seeds germinate in early spring (but not during summer) and require a period of cold stratification for breaking dormancy (<2 months). Natural enemies Surveys for natural enemies in the native area of the Caucasus were conducted in 2002 with the aim of identifying potential biological control agents (Seier et al., 2003). Many fungi were found associated with H. mantegazzianum, most species being new records for this host. However, none of the pests assessed, either insects or fungal pathogens, exhibited sufficient specificity to be considered safe for introduction into Europe (Cock & Seier, 2007). Uses and benefits Heracleum mantegazzianum has been widely grown as an ornamental plant in Europe, because of its striking appearance and usefulness in flower arranging. It is reported to be widely sown in Switzerland by bee-keepers to increase food resources for bees (Westbrooks, 1991). Heracleum sosnowskyi has been cultivated for silage and honey production in Russia and the Baltic States. Average yield of green matter reached 50–100 t ha−1 in the third year of growing. Honey yield per plant was theoretically 12.7 g from one plant or 270 kg ha−1. In Russia, two cultivars were grown, ‘Uspekh’ and ‘Severzhanin’. Heracleum persicum has also been used as an ornamental. Pathways of movements Natural dispersal Propagation is exclusively by
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