Short description of Heracleum persicum,

Heracleum persicum is a tall, perennial hogweed that grows in disturbed semi-natural habitats. Unlike all other ‘Giant Hogweeds’ recorded in the UK it is polycarpic and can spread via vegetative growth.

Impact summary: Heracleum persicum,

Heracleum periscum is highly invasive in Scandinavia, especially in Norway, where it changes the composition of invaded habitats. The plant sap is phytotoxic and induces phytocontact allergy when exposed to UV-radiation.

Habitat summary: Heracleum persicum,

Disturbed, semi-natural habitats such as road and rail verges, waste ground, river and stream banks, coastal beaches, disused agricultural land and meadows.

Overview table

Environment	Terrestrial
Species status	Non-Native
Native range
Functional type	Land plant
Status in England
Status in Scotland
Status in Wales
Location of first record
Date of first record	1820

Origin

Iran (widespread), Iraq (very local) and Turkey (very local).

First Record

The earliest record of Heracleum persicum from Europe is as an ornamental introduction to Kew Gardens in 1819 (Rijal et al., 2015; and not 1829 as widely cited). Recent research suggests that it was also independently introduced from Iran to Denmark at about the same. English material was then introduced to Finland and from there to Norway (Rijal et al., 2015).

Pathway and Method

Originally grown for ornament at Kew Gardens and then widely distributed for ornamental planting elsewhere, including to within the grounds of Buckingham and Kensington Palaces, where it still occurs today. The dispersal of seed from ornamental plantings along watercourses is likely to be the source of most established populations in the UK.

Species Status

The species is invasive in Scandinavia (Denmark, Norway, Sweden, Finland) and Iceland. It has also been recorded in Latvia, Estonia, Czech Republic, Hungary and UK but it’s status in the latter is poorly understood due to confusion with other Giant Hogweeds. H. mantegazzianum sensu lato appears to include at least five introduced species in the UK (Denness et al., 2013), including H. persicum, but the vast majority of records have not been critically assessed.

Dispersal Mechanisms

The relatively large seeds of Heracelum persicum are likely to be dispersed locally by wind/gravity with long distance dispersal by hydrochory where it occurs close to water courses

Reproduction

Unlike other Giant Hogweeds Heracleum persicum is a polycarpic perennial that generally attains a height of 2-5 (-3) m. It can repeatedly flower and spread by vegetative (clonal) reproduction if seed production fails. It is probably protandrous and therefore largely outcrossing but this requires confirmation. Only the primary umbels produce seed, later umbels just producing pollen. Like other Giant Hogweeds seed production is high (1600-4000 seeds per plant) although possibly lower than in H. mantegazzianum sensu stricto. Seed germination requires stratification at 2-4°C for two months and flowering starts after the third year post germination.

Known Predators/Herbivores

Only one known - a nematode.

Resistant Stages

Clonal growth allows Heracleum persicum to survive at higher latitudes with shorter growing seasons and colder temperatures than other Giant Hogweed species.

Habitat Occupied in GB

No information (see Distribution).

There are currently less than a dozen records of Heracleum persicum in the UK but only one has been confirmed by genetic analyses (Buckingham and Kensington Palaces; Jahodová et al., 2007; Rijal et al., 2015).

Environmental Impact

Heracleum persicum reduces the abundance of native species through shading/competition and allelopathy. It can also hybridise with native H. sphondylium which is a very rare species in Scandinavia. It also alters soil composition and causes erosion where monocultures exclude all other species.

Health and Social Impact

The plant sap is phytotoxic and induces phytocontact allergy and burns when exposed to UV-radiation. Despite these properties, Norwegians have a strong cultural association with the plant, especially in Tromsø where it is included in a variety of local traditions. However, dense stands can restrict access to recreational areas and reduce aesthetic beauty of invaded habitats with potential knock-on effects for tourism and fishing.

Economic Impact

The costs of controlling Heracleum persicum in Scandinavia have not been quantified but are thought to be substantial, especially in the province of Tromsø where it is controlled by chemical and mechanical means.

Identification

CABI 2017. Invasive Species Compendium: Heracleum persicum (Persian Hogweed). http://www.cabi.org/isc/datasheet/120209.

Biology, ecology, spread, vectors

CABI 2017. Invasive Species Compendium: Heracleum persicum (Persian Hogweed). http://www.cabi.org/isc/datasheet/120209. EPPO 2009. Heracleum mantegazzinaum, H. sosnowskyi and H. persicum. EPPO Bulletin 39, 465-470.

Management and impact

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, 99-114. Rijal, D.P., Torbjorn, A.L.M., Jahodova, S., Stenoien, H.K. & Alsos, I.G. 2015. Reconstructing the invasion history of Heracleum persicum (Apiaceae) into Europe. Molecular Ecology 24, 5522-5543.

General

Denness, A., Armitage, J.D. & Culham, A. 2013. A contribution towards the identification of giant hogweed species (Heracleum, Apiaceae) naturalised in the British Isles with comments concerning their furanocourarin content. New Journal of Botany 3, 183-196.