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Giant hogweed

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Contents
  1. Etymology
  2. Description
  3. Identification
  4. Life cycle
  5. Reproduction and spread
  6. History of introduction
  7. Health hazards
  8. Ecological impact
  9. Control
  10. Legal status
  11. In culture
  12. See also
  13. References

“Hogweed” redirects here. For other uses, see Hogweed (disambiguation).

This article is about the invasive giant hogweeds. For the native species of meadows and verges, see Common hogweed. For practical advice, see Control of giant hogweed.

The neutrality of this article is disputed. Relevant discussion may be found on the talk page. Please do not remove this message until conditions to do so are met. (May 2026)

Giant hogweed is the common name for several species of very tall, invasive flowering plants in the genus Heracleum of the carrot family, Apiaceae — principally Heracleum mantegazzianum, H. sosnowskyi and H. persicum.1 Native to the Caucasus and south-west Asia, they were brought into Europe during the nineteenth and twentieth centuries, first as ornamental curiosities and later as high-yield fodder. All three have escaped cultivation and are now counted among the most problematic invasive plants of the Northern Hemisphere.2

A mature plant can reach 5 metres (16 ft) in height, with a hollow, purple-blotched stem and a flat-topped compound umbel up to 80 cm across.3 A single plant sheds on average some 20,000 seeds, and exceptionally more than 46,000; the terminal umbel alone produces nearly half of them.4 The seeds settle in the upper layer of the soil, where they form a seed bank that outlives the parent plant.5

The sap contains furanocoumarins, which make skin acutely sensitive to sunlight. Contact itself is painless: injury appears only after the skin has been exposed to light, typically a day or two later, and its marks may last for months or years.6 Because of this delay, many of those affected do not connect their injuries with the plant.

Control is difficult and, when poorly executed, counter-productive. Cutting or mowing without destroying the root does not kill the plant; it regrows from buds on the crown and flowers again, often with more heads than before.78 Lasting control treats the root, continues for several seasons until the seed bank is exhausted, and is co-ordinated across every property in the affected catchment.3

Etymology

The English name hogweed was applied from at least the early eighteenth century to plants “eaten by hogs, or deemed fit only for them”; the leaves of the native common hogweed were gathered as pig fodder.9 The generic name Heracleum, published by Linnaeus in 1753, is usually taken to refer to Heracles, although Linnaeus himself glossed it as honouring Heraclides, the father of Hippocrates (see Heracleum).10 If it is Heracles, the association is apt: the plant’s response to cutting recalls the Lernaean Hydra, which grew two heads for each one removed (see hydra effect).

The specific epithets honour two men. Mantegazzianum was given by the Florentine botanists Sommier and Levier, who brought seed back from the Caucasus in 1890, to their friend Paolo Mantegazza (1831–1910), physiologist and anthropologist, who never wrote about the plant.11 Sosnowskyi honours the Caucasian botanist Dmitrii Sosnowsky (see Sosnowsky’s hogweed).

In Russian the genus is called borshchevik (борщевик) and in Polish barszcz; both words originally named the plant itself, from which an early form of borscht was made.12 In Poland a lacto-fermented soup of common hogweed, first recorded in 1595, was eaten in Lent by the professors of the Jagiellonian University in Kraków. By the eighteenth century it had become a food of the poor, and beetroot took over both the dish and its name.13

Description

Plate II Compound umbel

Anatomy of the compound umbel. Up to 150 rays spring from a single point at the top of the stem; each carries an umbellet of small white flowers.

Giant hogweed is a monocarpic perennial. For several years it grows only as a rosette of large leaves, accumulating reserves in a stout taproot; then, in a single season, it produces a flowering stem, sets seed and dies.14

Stem. The flowering stem is usually 2–4 m tall and exceptionally 5 m, 5–10 cm and exceptionally up to 15 cm in diameter at the base,4 hollow, ridged and covered with coarse bristles. It is marked with dark purple blotches, or is purple throughout.3

Leaves. The basal, or radical, leaves are up to 3 m long, deeply divided into three to five segments with sharply toothed lobes. Leaves higher on the stem are smaller.

Inflorescence. The terminal umbel is up to 80 cm across, and has been measured at 85 cm. It is made up of 30 to 150 rays, each ending in a smaller umbel of white flowers, and is surrounded by satellite umbels on side branches, which flower a little later.34 A plant carries up to four orders of umbels, and the lower the order, the less seed it sets; see Umbel.

Fruit. Each flower yields a dry, flattened fruit which splits into two mericarps, usually called seeds, about 1 cm long and marked with conspicuous, club-shaped oil ducts (vittae).

Root. The taproot is thick and fleshy. The shoots arise from buds on the crown, at or just below the surface. What the passer-by sees — stem, leaves and umbels — is only the visible superstructure: it is renewed each year from the base.

Apical dominance

As in most plants, the growing tip suppresses the development of lateral buds. When the terminal umbel is removed — decapitation, in the horticultural sense — the lateral buds are released and grow out, producing several smaller umbels in its place. In a field study, nearly half of all plants whose umbels had all been cut off regenerated in the same season, and umbels cut at the early fruiting stage and left lying on the ground still ripened a fifth of their normal crop.8

Identification

Most tall umbellifers are harmless, and misidentification is common in both directions. Giant hogweed is distinguished chiefly by its size.

Giant hogweed and its common look-alikes
SpeciesHeightStemUmbelHazard
Heracleum mantegazzianum
giant hogweed		2–5 m5–10 cm, purple blotches, bristlyup to 80 cmsevere
Heracleum sosnowskyi
Sosnowsky’s hogweed		1.5–3 mpurple-spotted, ribbed30–50 cmsevere
Heracleum sphondylium
common hogweed		to 2 mhairy, green, occasionally flushed purpleup to 20 cmmild
Anthriscus sylvestris
cow parsley		to 1.5 mgreen, hollow, downyup to 10 cmnone
Angelica sylvestris
wild angelica		to 2 msmooth, often purple-tingedup to 15 cmslight

When in doubt, observers should not touch the plant, should photograph it with an object for scale, and should report it to the local authority.

Life cycle

Fig. 1 Life cycle

The life cycle of a monocarpic perennial. The cycle can be written S → P → S′, where the seed produced (S′) far exceeds the seed that began it (S).

Seeds are shed from late summer onwards. They are dormant when shed and germinate only after a period of cold, moist conditions — stratification, supplied in nature by winter; in the laboratory about two months at 2–4 °C suffices.15 Germination takes place in early spring, often at very high densities.

In the invaded range most plants flower in their third or fourth year; on pasture and in the native Caucasus they flower later.7 Flowering is postponed, not abandoned, when conditions are poor: a plant that is grazed, shaded or short of nutrients simply waits, persisting as a rosette on the reserves in its root.3 The oldest individual on record flowered at the age of twelve, on an unusually dry site.7 Flowering is the plant’s highest and final stage: once it has begun, the plant dies at the end of the season even if it is cut down, and in an experiment none of twenty cut plants lived to the next year.16

Reproduction and spread

Giant hogweed reproduces only by seed. The terminal umbel produces about 45 per cent of a plant’s seed, the satellite umbels 29 per cent, and umbels on lower branches most of the remainder.4 The seed that reaches the ground forms a short-lived but abundant seed bank, 95 per cent of it in the top 5 cm of soil.5 About 9 per cent of buried seed survives its first year, 3 per cent its second and 1 per cent its third;15 a very few survive seven years.17

Wind moves most seed only a few metres: 60–90 per cent lands within 4 m of the parent.3 Accounts that credit the plant’s spread to the invisible hand of the wind overstate its role. Long-distance dispersal is the work of water — floods carry seed kilometres downstream along rivers18 — and, above all, of people, who move seed in soil, on tyres and mowers and in dried flower heads.3 Stands therefore follow the routes of trade: rivers, roads and railways.

In a well-established stand the plant’s reproductive return consistently exceeds the growth of the vegetation it displaces; once r > g, dominance becomes self-reinforcing.[clarify]

History of introduction

Fig. 2 Invaded range in Europe

Where each giant hogweed is the characteristic invader: # H. mantegazzianum, % H. sosnowskyi, @ H. persicum; + the native range in the Caucasus. Schematic, by country; after EPPO and Jahodová et al.1

Britain and western Europe

H. mantegazzianum appears on the seed list of the Royal Botanic Gardens, Kew, in 1817. It was admired by nineteenth-century gardeners for its size and planted on estates and in parks; the first record of the plant growing wild dates from 1828, at Shelford in Cambridgeshire.3 In The Wild Garden (1870) William Robinson recommended the giant cow parsnip for rich soil near river banks, wherever a striking effect was wanted at a distance.19 By the edition of 1883 he was advising that the plants, which sow themselves, should not be allowed to monopolise the ground.20 From the gardens it followed rivers into the countryside, and by the late twentieth century it lined watercourses throughout Britain and much of western and central Europe.14

Soviet Union and successor states

Main article: Sosnowsky’s hogweed

H. sosnowskyi was described from the Caucasus by the botanist I. P. Mandenova in 1944. From 1947 it was trialled as a silage crop at the Polar-Alpine Botanical Garden in Kirovsk, with seed collected near Nalchik, and it was subsequently promoted for its extraordinary productivity: between 1962 and 1966 some 5,500 kg of seed of the new silage plants were sent to nearly 1,500 farms.21 Cultivation stopped in the 1980s.22

The decisive expansion followed the end of collective management of the land. As collective farms were dissolved in the late 1980s and 1990s, large areas of farmland were abandoned, and the plant spread from former fields and silage pits into meadows, roadsides and villages across the region.22 Genetic analysis has since suggested that some of the founding plants of the Soviet trials were in fact H. mantegazzianum.23 H. sosnowskyi was struck off the Russian State Register of breeding achievements in 2012, as having lost its economic usefulness, and added to the national classifier of weeds in 2015.24

Scandinavia

Main article: Persian hogweed

H. persicum was introduced to Norway as an ornamental in the 1830s. It began spreading from gardens towards the end of the nineteenth century and is today a familiar sight in the towns of northern Norway, where it is known as the Tromsø palm.25

North America

Giant hogweed was introduced to North America in the early twentieth century as a garden curiosity, and was present in New York State by about 1917.26 It is listed as a federal noxious weed in the United States.27

Health hazards

Fig. 3 Mericarp, ×6

A mericarp, showing the club-shaped vittae. Sap is present in every part of the plant, seeds included.

Main article: Phytophotodermatitis

The sap of giant hogweed contains linear furanocoumarins, which bind to the DNA of skin cells when activated by ultraviolet light. The result is a severe burn — phytophotodermatitis — which develops only after exposure to light, typically over 24 to 72 hours.6 The skin may remain darkened for months and sensitive to sunlight for several years.3 Sap in the eyes is a medical emergency.

Children are at particular risk: attracted by the plant’s size, they use the hollow stems as pea-shooters or telescopes.3 Cutting the plant with a strimmer throws sap over the operator, a hazard first described in grounds staff as “strimmer rash”.28

First aid. Wash the skin at once with soap and plenty of cold water, keep the area covered and out of sunlight for at least 48 hours, including on dull days, and seek medical advice.6

Ecological impact

Giant hogweed forms dense stands in which a single species takes most of the light. Its leaves unfold early and cast deep shade: five centimetres above the ground, the share of daylight is on average 56 per cent lower than in uninvaded grassland.29 Invaded plots in the Czech Republic held 40 per cent fewer plant species than uninvaded ones,30 and in a comparison of adjacent plots, about half as many.31 Claims that the canopy benefits the plants growing under it have not been substantiated; nothing trickles down.[citation needed]

The damage is not permanent. At grasslands invaded for up to 48 years, native species tended to recover after about 30 years, while the hogweed declined, apparently undermined by changes in its own soil (see Enemy release hypothesis).32 When the plants die back in winter they are reported to leave riverbanks bare and prone to erosion.33

The plant’s nectar is visited by many insects, and some beekeepers[who?] continue to regard the species as a net benefit to the community.[dubious – discuss] In twentieth-century Germany it was propagated as a bee plant, and deliberate sowing by beekeepers probably explains its appearance in remote places.34 A survey of twenty Czech sites found its visitors numerous but few in kind, dominated by a handful of generalist flies and the honey bee, and concluded that the plant is not a necessary resource for local flower visitors (see Umbel § Pollination).35

Control

Main article: Control of giant hogweed

Methods differ chiefly in whether they destroy the root. Mowing, strimming and the removal of flower heads prevent seeding for a season at best and prolong the life of the plant;8 cutting the taproot at least 10 cm below the soil surface kills it.3 Because the seed bank persists for several years, a programme must continue until no new seedlings appear, and because seed moves downstream, it must cover the whole catchment. No safe biological control agent has been found: a search of the plant’s native range in the Caucasus found no natural enemy specific enough to be released.36

In Great Britain giant hogweed is listed in Schedule 9 of the Wildlife and Countryside Act 1981, which makes it an offence to plant it or otherwise cause it to grow in the wild.37 In the European Union H. sosnowskyi and H. persicum were placed on the list of invasive alien species of Union concern in 2016,38 and H. mantegazzianum was added in 2017.39 Listed species may not be imported, kept, grown or sold, and member states must manage established populations. Since 1 March 2026 Russian law has obliged holders of land to destroy dangerous invasive plants listed by their region, on pain of losing the land.40

In culture

“The Return of the Giant Hogweed”, on the Genesis album Nursery Cryme (1971), tells of a Victorian explorer who brings the plant from Russia to Kew; it escapes, spreads, and survives every attempt to destroy it.41 It has been connected with British press reports of children burned by the plant in the summer of 1970.11 The album entered the British charts only in 1974, at number 39.42 The standard scientific monograph on the plant opens one of its chapters with an epigraph from the song.43

See also

Footnotes

  1. Jahodová, Š.; Trybush, S.; Pyšek, P.; Wade, M.; Karp, A. (2007). “Invasive species of Heracleum in Europe: an insight into genetic relationships and invasion history”. Diversity and Distributions. 13 (1): 99–114. doi:10.1111/j.1366-9516.2006.00305.x. ↩ ↩2

  2. Pyšek, P.; Cock, M. J. W.; Nentwig, W.; Ravn, H. P., eds. (2007). Ecology and Management of Giant Hogweed (Heracleum mantegazzianum). Wallingford: CAB International. ISBN 978-1-84593-206-0. doi:10.1079/9781845932060.0000. ↩

  3. Nielsen, C.; Ravn, H. P.; Nentwig, W.; Wade, M., eds. (2005). The Giant Hogweed Best Practice Manual: Guidelines for the management and control of an invasive weed in Europe. Hørsholm: Forest & Landscape Denmark. ISBN 87-7903-209-5. ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7 ↩8 ↩9 ↩10 ↩11

  4. Perglová, I.; Pergl, J.; Pyšek, P. (2006). “Flowering phenology and reproductive effort of the invasive alien plant Heracleum mantegazzianum”. Preslia. 78: 265–285. ↩ ↩2 ↩3 ↩4

  5. Krinke, L.; Moravcová, L.; Pyšek, P.; Jarošík, V.; Pergl, J.; Perglová, I. (2005). “Seed bank of an invasive alien, Heracleum mantegazzianum, and its seasonal dynamics”. Seed Science Research. 15 (3): 239–248. ↩ ↩2

  6. New York State Department of Environmental Conservation. “Giant Hogweed”. Retrieved 26 September 2026. ↩ ↩2 ↩3

  7. Pergl, J.; Perglová, I.; Pyšek, P.; Dietz, H. (2006). “Population age structure and reproductive behavior of the monocarpic perennial Heracleum mantegazzianum (Apiaceae) in its native and invaded distribution ranges”. American Journal of Botany. 93 (7): 1018–1028. doi:10.3732/ajb.93.7.1018. ↩ ↩2 ↩3

  8. Pyšek, P.; Krinke, L.; Jarošík, V.; Perglová, I.; Pergl, J.; Moravcová, L. (2007). “Timing and extent of tissue removal affect reproduction characteristics of an invasive species Heracleum mantegazzianum”. Biological Invasions. 9 (3): 335–351. doi:10.1007/s10530-006-9038-0. ↩ ↩2 ↩3

  9. “hogweed”. Online Etymology Dictionary. Retrieved 26 September 2026. ↩

  10. Burkhardt, L. (2018). Verzeichnis eponymischer Pflanzennamen – Erweiterte Edition. Berlin: Botanic Garden and Botanical Museum Berlin. doi:10.3372/epolist2018. ↩

  11. Fagioli, S. (2024). “Mantegazza pop. Dall’Heracleum mantegazzianum di Sommier & Levier a The return of the Giant Hogweed dei Genesis e oltre”. Archivio per l’Antropologia e la Etnologia. 154: 83–97. doi:10.36253/aae-3089. ↩ ↩2

  12. Vasmer, M. Etymological Dictionary of the Russian Language, s.v. “борщ”. ↩

  13. Łuczaj, Ł.; Szymański, W. M. (2007). “Wild vascular plants gathered for consumption in the Polish countryside: a review”. Journal of Ethnobiology and Ethnomedicine. 3: 17. doi:10.1186/1746-4269-3-17. ↩

  14. Tiley, G. E. D.; Dodd, F. S.; Wade, P. M. (1996). “Biological Flora of the British Isles No. 190: Heracleum mantegazzianum Sommier & Levier”. Journal of Ecology. 84 (2): 297–319. doi:10.2307/2261365. ↩ ↩2

  15. Moravcová, L.; Pyšek, P.; Pergl, J.; Perglová, I.; Jarošík, V. (2006). “Seasonal pattern of germination and seed longevity in the invasive species Heracleum mantegazzianum”. Preslia. 78: 287–301. ↩ ↩2

  16. Pyšek, P.; Perglová, I.; Krinke, L.; Jarošík, V.; Pergl, J.; Moravcová, L. (2007). “Regeneration ability of Heracleum mantegazzianum and implications for control”. In Pyšek, P.; et al. (eds.). Ecology and Management of Giant Hogweed. Wallingford: CAB International. pp. 112–125. doi:10.1079/9781845932060.0112. ↩

  17. Moravcová, L.; Pyšek, P.; Krinke, L.; Müllerová, J.; Perglová, I.; Pergl, J. (2018). “Long-term survival in soil of seed of the invasive herbaceous plant Heracleum mantegazzianum”. Preslia. 90 (3): 225–234. ↩

  18. Trottier, N.; Groeneveld, E.; Lavoie, C. (2017). “Giant hogweed at its northern distribution limit in North America: experiments for a better understanding of its dispersal dynamics along rivers”. River Research and Applications. 33 (7): 1098–1106. doi:10.1002/rra.3149. ↩

  19. Robinson, W. (1870). The Wild Garden. London: John Murray. p. 78. ↩

  20. Robinson, W. (1883). The Wild Garden (new ed.). London: John Murray. ↩

  21. Shadrin, D.; Dalke, I.; Zakhozhiy, I.; et al. (2023). “Heracleum sosnowskyi or Heracleum mantegazzianum? DNA-based identification of invasive hogweeds (Apiaceae) in two key regions of the species’ invasion history in the territory of the former Soviet Union”. Research Square (preprint). doi:10.21203/rs.3.rs-3296382/v1. ↩

  22. Ozerova, N. A.; Krivosheina, M. G. (2018). “Patterns of secondary range formation for Heracleum sosnowskyi and H. mantegazzianum on the territory of Russia”. Russian Journal of Biological Invasions. 9: 155–162. doi:10.1134/S2075111718020091. ↩ ↩2

  23. Shadrin, D. M.; Dalke, I. V.; Zakhozhiy, I. G.; et al. (2024). “DNA barcode marker analysis of Heracleum sosnowskyi Manden. and Heracleum mantegazzianum Sommier & Levier (Apiaceae) from European Russia”. Russian Journal of Biological Invasions. 15 (3): 416–431. doi:10.1134/S2075111724700309. ↩

  24. Luneva, N. N.; Konechnaya, G. Yu.; Smekalova, T. N.; Chukhina, I. G. (2018). “On status of Heracleum sosnowskyi Manden. on the territory of Russian Federation”. Vestnik Zashchity Rastenii. 3 (97): 10–15. doi:10.31993/2308-6459-2018-3(97)-10-15. ↩

  25. Alm, T. (2013). “Ethnobotany of Heracleum persicum Desf. ex Fisch., an invasive species in Norway, or how plant names, uses, and other traditions evolve”. Journal of Ethnobiology and Ethnomedicine. 9: 42. doi:10.1186/1746-4269-9-42. ↩

  26. Gucker, C. L. (2009). “Heracleum mantegazzianum”. Fire Effects Information System. USDA Forest Service. doi:10.2737/feis-species-review-herman. ↩

  27. Code of Federal Regulations, title 7, § 360.200: Designation of noxious weeds. ↩

  28. Freeman, K.; Hubbard, H. C.; Warin, A. P. (1984). “Strimmer rash”. Contact Dermatitis. 10 (2): 117–118. doi:10.1111/j.1600-0536.1984.tb00357.x. ↩

  29. Jandová, K.; Klinerová, T.; Müllerová, J.; et al. (2014). “Long-term impact of Heracleum mantegazzianum invasion on soil chemical and biological characteristics”. Soil Biology and Biochemistry. 68: 270–278. doi:10.1016/j.soilbio.2013.10.014. ↩

  30. Pyšek, P.; Pyšek, A. (1995). “Invasion by Heracleum mantegazzianum in different habitats in the Czech Republic”. Journal of Vegetation Science. 6 (5): 711–718. doi:10.2307/3236442. ↩

  31. Hejda, M.; Pyšek, P.; Jarošík, V. (2009). “Impact of invasive plants on the species richness, diversity and composition of invaded communities”. Journal of Ecology. 97 (3): 393–403. doi:10.1111/j.1365-2745.2009.01480.x. ↩

  32. Dostál, P.; Müllerová, J.; Pyšek, P.; Pergl, J.; Klinerová, T. (2013). “The impact of an invasive plant changes over time”. Ecology Letters. 16 (10): 1277–1284. doi:10.1111/ele.12166. ↩

  33. Thiele, J.; Otte, A. (2007). “Impact of Heracleum mantegazzianum on invaded vegetation and human activities”. In Pyšek, P.; et al. (eds.). Ecology and Management of Giant Hogweed. Wallingford: CAB International. pp. 144–156. doi:10.1079/9781845932060.0144. ↩

  34. Thiele, J. (2007). Patterns and processes of Heracleum mantegazzianum invasion into German cultural landscapes on the local, landscape and regional scale. Doctoral dissertation. Giessen: Justus-Liebig-Universität. ↩

  35. Bogusch, P.; Vojtová, T.; Hadrava, J. (2023). “High abundance but low diversity of floral visitors on invasive Heracleum mantegazzianum (Apiaceae)”. NeoBiota. 86: 193–207. doi:10.3897/neobiota.86.100625. ↩

  36. European Commission, CORDIS. “Searching for effective biological control enemies for the giant hogweed”. Retrieved 26 September 2026. ↩

  37. Wildlife and Countryside Act 1981 (c. 69), s. 14 and Schedule 9. ↩

  38. Commission Implementing Regulation (EU) 2016/1141 of 13 July 2016. Official Journal of the European Union L 189: 4. ↩

  39. Commission Implementing Regulation (EU) 2017/1263 of 12 July 2017. Official Journal of the European Union L 182: 37. ↩

  40. Federal Law of the Russian Federation of 31 July 2025 No. 294-FZ “On amendments to the Land Code of the Russian Federation and certain legislative acts of the Russian Federation”. Official publication. ↩

  41. Genesis (1971). Nursery Cryme. Charisma Records. ↩

  42. Official Charts Company. “Nursery Cryme – Genesis”. Retrieved 26 September 2026. ↩

  43. Pyšek, P.; Müllerová, J.; Jarošík, V. (2007). “Historical dynamics of Heracleum mantegazzianum invasion at regional and local scales”. In Pyšek, P.; et al. (eds.). Ecology and Management of Giant Hogweed. Wallingford: CAB International. pp. 42–54. doi:10.1079/9781845932060.0042. ↩

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