Persian hogweed

“Tromsø palm” redirects here. For the film prize, see § In culture. For the invasive giant hogweeds in general, see Giant hogweed.

Persian hogweed (Heracleum persicum) is a tall perennial hogweed native to Iran and the neighbouring parts of Turkey and Iraq. In Iran its dried fruits are the spice golpar. In Norway, where it arrived as a garden plant in the nineteenth century, it is the Tromsø palm (Norwegian tromsøpalme): an unofficial emblem of the city of Tromsø, and an alien species of very high risk whose import, release and sale are banned.¹²³ Unlike the other two giant hogweeds invasive in Europe, which die after flowering once, it flowers year after year from the same root.⁴⁵

The two countries value the plant in opposite ways. In Iran golpar is gathered from the wild and sold in the herbal markets, and the Slow Food Foundation lists it among foods at risk of disappearing, citing declining wild stands.⁶⁷ In northern Norway it lines roads, shores and waste ground,² and the national risk assessment of 2018 found no possibility of getting rid of it there within the current interglacial.⁸ Fruits imported from Iran are sold in Norway’s immigrant grocery shops as a spice, at a price that, according to Artsdatabanken, makes it unlikely that anyone will sow them.²dear where it is wanted, free where it is not

Taxonomy

The name

The name Heracleum persicum first appeared in 1832, in a supplement to the catalogue of the Paris botanical garden, as a bare entry that gave the plant’s origin as Persia and said nothing else about it.⁹¹⁰ It was validly published in 1841 by F. E. L. Fischer, C. A. Meyer and J. L. E. Avé-Lallemant, in the list of seeds that the Imperial Botanical Garden of St Petersburg offered to other gardens in exchange.⁹¹¹ Their Latin description tells of a very showy plant about a fathom high, with liver-coloured leaf stalks and very large, sticky, strongly scented fruits; the seed had been sent by the collector Szovits from the province of Azerbaijan in northern Persia.¹¹ The name is therefore cited as H. persicum Desf. ex Fisch., C.A.Mey. & Avé-Lall.⁹offered for mutual exchange, not for sale

Several standard works, among them the Best Practice Manual for giant hogweed, date the species to 1829, the year of the main part of the Paris catalogue.⁵¹² The name is not in it.¹⁰

The Scandinavian plant

For more than a century the plant of northern Norway went under other names. The English visitor who sowed it near Hammerfest in 1836 called it Heracleum giganteum; others called it H. panaces; and twentieth-century Scandinavian floras used H. laciniatum, a name that properly belongs to another plant.¹³⁴¹⁴ In 1987 the botanist D. O. Øvstedal rejected H. persicum for the Tromsø plant, because it did not match Turkish herbarium specimens.⁴ A DNA study of the invasive hogweeds of Europe in 2007 grouped the plants labelled H. laciniatum with H. persicum,¹² and the Nordic flora of 2010 adopted the name.⁴

The identification is not quite closed. The ethnobotanist Torbjørn Alm left open the possibility of an unidentified hybrid.⁴ Artsdatabanken, Norway’s biodiversity information centre, assigns the plant to H. persicum with fair confidence, but notes a few genes not found in Iranian material.² A name proposed for the Norwegian plant alone, H. tromsoensis, remains unpublished.¹⁵

Golpar and other names

In Persian the plant is golpar (گلپر), and in the regional languages of Iran kolpar (Gilaki), kūla(k) (Mazandarani) and karso (Lori), among others.¹ Golpar is not a single species. Encyclopaedia Iranica applies the name to at least five aromatic hogweeds of the humid mountains of Iran, which are sold under one name because their users ignore the characters that tell them apart.¹ Most food and pharmacological studies take golpar to be H. persicum.¹⁶⁴

Some twenty Norwegian names have been recorded. Most are derived from the Latin genus name, such as herakleum, rakleum, orakleum and høyrakel, or borrowed from other umbellifers. A few were coined for this plant: stormtræ, “storm tree”, for the dead stems that stand through the winter gales; three pejorative names involving rats, “rat seed”, “rat poison” and “rat grass”; and tromsøpalme.⁴

The earliest written record of tromsøpalme that Alm could find is in a German guide to the flora and fauna of Norway written in 1944 for the occupying troops, which says that the soldiers called the plant the “Tromsö-Palme”. Alm reads it as a soldiers’ joke: the Arctic posting’s answer to the palms of the Mediterranean and Africa.⁴ The name spread in Norway after the war, became official when the standard Norwegian flora adopted it in 1963, and has since displaced most of the others.⁴ Other Nordic names are the Swedish tromsöloka, the Danish hårfrugtet bjørneklo, “hairy-fruited hogweed”, the Finnish persianjättiputki and the Northern Sámi romssaboska.^17181915

Description

Persian hogweed is a polycarpic perennial: after flowering it survives and flowers again from the same root, whereas giant hogweed and Sosnowsky’s hogweed die after flowering once.⁴⁵ It usually grows to about 1.5–2.5 m, and occasionally to more than 4 m.²²⁰ One root crown can send up several stems, as many as five, hollow and evenly purplish at the base. The leaves are pinnate, with two to four pairs of broad, bluntly toothed leaflets, and can be 2 m long. The umbels are domed rather than flat, 30–50 cm across.²¹¹⁷²² The whole plant smells of anise; the oil of its leaves and stems is dominated by anethole, the compound that gives anise its flavour.⁵²³²⁴

Most of the seed is set by the terminal umbels. The side umbels open after the terminal ones have set seed, and their female flowers usually wither, leaving them to serve as pollen donors, as the lower umbels do in giant hogweed.²⁵²¹ Estimates of the seed set by one plant range from 1,600–4,000 to 6,000–8,000, below giant hogweed’s.²¹¹⁴²² The seeds need about two months of cold before they will germinate,²⁵ and of one lot collected in northern Norway only 2 per cent germinated.²¹ Whether the plant also spreads by root shoots is disputed: several Nordic sources describe clonal growth where seed fails, while EPPO states that it does not reproduce vegetatively.²⁵²²²

From the short summer days of Persia the plant has moved into continuous daylight: its range in Europe spans about 51° to 71° N.²⁵ In northern Norway it starts growing as the snow melts, around the end of March, and flowers from July to late August.²¹ In the 1870s it ripened fruit even at Vardø, at 70°22′ N, where the mean temperature in July is below 10 °C.⁴ The dead stems stand through the winter and appear in the local papers every year.⁴

Plants in Europe carry on average about 42 per cent less genetic diversity than those of the native range, and Norwegian populations have lost about half of theirs. The Norwegian populations are nonetheless the most abundant and vigorous in Europe.²⁵

Golpar

The dried fruits, bitterish and aromatic, are the part most used. Iranian cooking counts golpar as a “hot” spice and sprinkles it on foods reckoned “cold” and flatulent: broad beans, beans, potatoes and pomegranate seeds. It is also stirred into the vinegar in which lettuce leaves are dipped.¹ The tender leaves and leaf stalks are pickled as golpar torši,¹ and the ground seeds season soups, omelettes and fish.⁷ The oil of the fruits, yielded at 1.6–4.9 per cent by wild Iranian populations, consists mostly of esters, above all hexyl butyrate and octyl acetate.²⁶²⁷ Their proportions vary from one population to another, and Iranian researchers have proposed choosing the richest for cultivation.¹⁶

Whole fruits are burned with the seeds of wild rue as a fumigant. In the past they were scattered on the shroud and in the coffin when a body had to be carried to a distant cemetery, probably to mask the smell.¹ Folk medicine uses golpar for digestion and pain, among much else; in rodents the oil and extracts of the fruit have shown analgesic and anti-inflammatory effects.¹²⁸

Golpar is mostly gathered from the wild, and its seasonal harvest and sale add to incomes in mountain villages. The Slow Food Foundation, which lists it in its Ark of Taste, reports that rising demand, overharvesting and changes in land use have reduced the wild stands in some regions.⁷

Outside Iran the spice meets plant-health law. American inspectors often find golpar in the luggage of passengers from Iran and seize it as the seed of a federal noxious weed, filed under giant hogweed.²⁹³⁰ In April 1989 an inspector found large quantities of it for sale in food shops in Los Angeles. The invoices showed that it had been imported under its Persian name; the importer helped to recall and destroy it; and 35 per cent of the seed proved viable.²⁹ The European Union’s list of invasive species gives Persian hogweed, alone among the hogweeds, a customs heading for “associated goods”: plants and parts of plants used in perfumery or pharmacy.³¹a spice at one border, a weed at the next

History in Europe

Arrival

The seed lists of the Royal Botanic Gardens at Kew record Persian hogweed as received in 1819, the earliest record of the species in Europe.⁵²⁵

On 18 July 1836 William Christy, an English naturalist who had sailed out with one of the directors of the English-owned copper mines at Alta, landed on the Fugleness peninsula across the bay from Hammerfest. In an old enclosure that had once been a burial ground, around the only tomb still standing, he sowed several garden plants, lupins and Californian poppies among them, and “the stately Heracleum giganteum”.¹³ Alm regards Christy’s seed, brought from England at a time when hogweed seed was widely advertised there, as the likely source of the Norwegian plant, and credits him with sowing it at other places in western Finnmark as well, including the mining settlement of Kåfjord.⁴ Christy’s published account describes only the sowing at Fugleness.¹³

The plant was taken from Alta to Tromsø about 1850. By the 1860s it was a favourite of small coastal gardens in Finnmark; in 1895 it was said to grow almost as a weed in Sør-Varanger; and in 1901 the flora of Tromsø treated it as established.⁴ The first herbarium specimens date from 1897, at Trondheim, and 1899, at Tromsø.²

Northern gardeners planted it for ornament and for shelter. In the treeless villages of the outer coast it served as a windbreak, at Honningsvåg as a hedge 20–30 m long, and in 1898 rows of it surrounded a whaling station on Skorøya. It was still being planted in graveyards in the late twentieth century.⁴ In the 1930s it was tried at Tromsø as fodder. The cows ate it willingly, but their milk tasted of it, and the trial was abandoned.⁴ The Soviet silage programme based on Sosnowsky’s hogweed later met the same objection on a larger scale.³²

Routes

                 I R A N
  (most likely Mazandaran, near Tehran)
          |                  |
          v                  v
       DENMARK            ENGLAND
    escaped 1888    Kew seed list 1819
                             |        :
                             v        :
                          FINLAND     : English seed
                       escaped 1871   : sown near
                             |        : Hammerfest,
                             |        : 1836
                             v        v
                            N O R W A Y
                      first specimens 1897-99
                                 |
                                 v
                              SWEDEN
                   in part from Norwegian plants
                    sown at Vilhelmina in 1946

|  genetic reconstruction (Rijal et al. 2015)
:  older account (Christy 1837; Alm 2013)

Genetic studies have revised the story. Comparing 578 plants at 27 microsatellite loci, Dilli Rijal and colleagues found two independent introductions from Iran, most likely from Mazandaran near Tehran: one to Denmark and one to England. Finland was colonised from England, and Norway from Finland rather than directly from England.²⁵ As a link between Finland and Norway they point to the copper works at Kåfjord in Alta, English-owned and in 1835 the largest settlement in Finnmark, which in 1840 employed 651 workers, with Finns the largest group among them.²⁵ A later study found multiple introductions from multiple source populations.³³capital from England, labour from Finland, seed from both

Folk tradition had its own explanations. Many in northern Norway believed that the plant had come from Russia with the Pomor trade, and at Loppa some said it came from Germany; Alm found no evidence for a Russian origin.⁴ In a later paper he examined such stories of plants “introduced by foreigners” across Norway, asking whether they were xenophobic tales.³⁴

Elsewhere in Europe

Outside Norway the species is scarcer. In Finland, where it had escaped from cultivation by 1871, 71 localities were known in 2015. In Denmark, where the first escaped plant was found in 1888, it occupies 2 of the 1,300 squares of the national atlas.¹⁷¹⁸²⁵ In Sweden, where it was first found in 1935, many of the stands of Norrland seem to descend from Norwegian plants sown at Vilhelmina in 1946; it spreads little there, perhaps because its pollen is often infertile.¹⁷

Plants provisionally identified as giant hogweed in two London parks, Kensington Gardens and the grounds of Buckingham Palace, proved genetically closer to Persian hogweed, as did park plants in Riga and Ērgļi, in Latvia, which may be hybrids.¹² No naturalised population is known in Britain.²⁵

Ecology

In Norway Persian hogweed grows on roadsides, waste ground, old meadows and pastures, abandoned farmland and shores, where it can form borders kilometres long behind the drift lines of seaweed; it increasingly enters forest edges and birch and alder woods, where it rarely flowers but can persist in half-shade for a long time.²²⁰ The winged fruits travel short distances on the wind and further by water or with birds. Stands on islands without other plants suggest that the fruits can float for kilometres at sea and strand still viable. Passing traffic carries them along roads, and moved soil carries both seeds and pieces of root.²²⁰

In a comparison of 56 pairs of invaded and uninvaded plots in northern Norway, the invaded plots had lower native cover, diversity and biomass, and on average almost two fewer native species.³⁵ Experiments under its canopy attributed the loss mainly to shade; the chemicals the plant releases played only a minor part.³⁶ Its seeds contain furanocoumarins that inhibit the germination of other plants.³⁷

In Norway it crosses with the native Siberian hogweed, H. sphondylium subsp. sibiricum. The hybrid, first found in 1967 and known as the polar palm (polarpalme), is fertile and vigorous, is itself a problem plant, and passes genes into the native plant.²²⁵¹⁷ See Common hogweed.

Health

The sap is phototoxic. Studies at Tromsø in the early 1980s, under the name H. laciniatum, isolated five furanocoumarins, of which bergapten was the most active. Leaves and flowers were strongly phototoxic and the stems hardly at all; the roots of older plants were strongly phototoxic even when dug out of frozen ground in December.³⁸³⁹ Phytophotodermatitis from the plant was then common in Tromsø in summer,⁴⁰ and two volunteers in the experiments accidentally acquired a photocontact allergy to three of its compounds.⁴¹ In its native range, a man in south-eastern Turkey developed blistering burns after mowing a field in which it grew.⁴²

Artsdatabanken considers it less dangerous in this respect than several of its relatives, noting that northern children have played with it for years without notable harm.² Alm records their games: blowpipes cut from the hollow stems, firing peas or rowan berries, which left sores around the mouth; water squirts; swords; hiding places in the stands, where the smell of the plant covered the smell of tobacco; and pretend binoculars that left sore rings around the eyes.⁴

Control and law

Norway placed the species on its black list in 2007 and has classed it as a very high risk since 2012. Since 2016 its import, release and sale have been banned under the regulation on alien organisms.⁴³²³ The European Union added it to its list of invasive alien species of Union concern in 2016.³¹ Tromsø municipality counts it among the most troublesome alien plants: owners may keep the plants they have, but must not let them spread, plant new ones or exchange seed.⁴⁴

A study published in 2017 found that the municipality controlled the plant only sporadically, for lack of staff and money, as part of its routine mowing of verges, parks and graveyards. It had no powers over private land, and its officials did not believe that the plant could be eradicated from Tromsø island.¹⁴ A survey of the island’s landowners in 2012 found that 38 per cent believed their plants had come from the neighbouring plots. Asked what they did with what they cut, 44 per cent said they composted it on the spot and 32 per cent that they left it on the ground.¹⁴it always comes from next door

Household remedies have included grazing by sheep in early spring, cutting the flowering stems, digging, and above all salt from the fish plants, sometimes boiled; fuel oil, petrol, paraffin, ammonium chloride and sour milk have also been tried.⁴ Mowing two or three times a season failed in northern Norway: the stands grew denser, and some plants flowered all the same.²¹ Digging the plants out below the growing point, repeated every year on islands off Tromsø, took about 70 hours of work a hectare in the first year and 3 hours in the fourth (see Control § Root cutting).¹⁷ A cyst nematode that attacks the plant in Iran has been suggested for biological control but has never been tested.²⁵²¹

Alm called eradication in northern Norway inconceivable, if only because of the cost.⁴ The national assessment of 2018 found no possibility of it within the current interglacial;⁸ that of 2023 thought local eradication possible, on small islands for example, but expensive and labour-intensive.² In 2007 the Directorate for Nature Management granted 50,000 kroner to an environmental organisation for the campaign against the plant.⁴³easier to imagine the end of the interglacial

In culture

In Tromsø everyone knows the plant, including people who otherwise ignore plants, and it is either loved or hated.⁴ Some residents regard it as a symbol of the city and a source of local identity.¹⁴ The city’s activity centre for the elderly is called Heracleum; a school revue named Tromsøpalmen has run since 1990; and the Tromsø International Film Festival awards prizes of the same name.⁴ In 2025 the festival’s Tromsø Palm for the best short film in its “Films from the North” programme went to In My Hand, and a Tromsø Palm for the best feature film was awarded for the first time.⁴⁵

Attempts at eradication have drawn letters to the newspapers calling the plant part of the city’s soul and identity. A society of its friends has been proposed, and so has replacing the reindeer on the city’s coat of arms with it. Some writers deny that the sap does any harm, citing generations of children at play, and one claimed that the plant was native, having survived the Ice Age in caves on Tromsø island.⁴ When Crown Prince Haakon married in 2001, a live plant, or a glass engraved with one, was suggested as the city’s gift. The umbels appear in the design of the Tromsø folk costume.⁴¹⁴

The dead stems and umbels are a favourite subject of winter photographs and a motif for jewellery and decorations, and flutes are made from the stems. The North Norwegian Art Museum owns Log, a sculpture by Stuart Frost made entirely of rings cut from the hollow stems.⁴ Artists of the Tromsø Arts Association once invited the public to taste a soup made from the plant.¹⁴

Alm used the plant to argue that modern, urban societies go on creating plant lore: its twenty-odd names and all its uses and customs arose in less than 180 years, most of them after 1900.⁴

See also

• Giant hogweed
• Sosnowsky’s hogweed
• Heracleum
• Common hogweed
• Lag phase