Regulated invasive species of Union concern under the European Regulation on the prevention and management of the introduction and spread of invasive alien species [1143/2014].
Introduction pathways - 1
Escape from Confinement
Introduction pathways subclass - 1
Introduction pathways - 2
Introduction pathways subclass - 2
NAPRA Ireland risk assessed
Large perennial herb. Reaches heights of up to 3m (CABI, 2015). One to five hollow stems, covered in stiff hairs and with a purple base. Stems may also be covered in purple blotches (CABI, 2015). Leaves may be up to 2m long with hairy undersides. Two to four pairs of serrate leaflets (CABI, 2015). Flowers held on umbels (umbrella-shaped heads) that can be 80cm wide (Nielsen et al., 2005). Each umbel is made up of many small white flowers. Can be up to 80,000 flowers on a single plant (Nielsen et al., 2005). Flowers from June to August, usually flowering first 3 years after germination (Rijal et al., 2015). The whole plant has a distinct aniseed smell (CABI, 2015). Stem and leaves contain a phototoxic sap that causes burning, blistering and swelling of the skin when exposed to sunlight (Nielsen et al., 2005; EPPO, 2009a). Heracleum spp. hybridize readily, which can make identification more difficult (EPPO, 2009a).
Heracleum persicum reduces biodiversity in the varied habitats it infests. Its dense stands, height, large leaves and early, fast growth (Rijal et al., 2015) outshade smaller native plants creating a 'giant hogweed landscape' (Nielsen et al., 2005). The leaves contain allelopathic chemicals which interfere with the germination of the seeds of other plants (CABI, 2015). Heracleum spp. hybridize readily (EPPO, 2009a). The native H. sphondylium is described in the CABI factsheet (2015) as 'almost rare' in northern Norway due to hybridization with H. persicum. Continued eutrophication may allow this nitrophilous weed to expand its range (Laivins & Gavrilova in EPPO, 2009a). Dieback during the autumn leaves bare soil exposed to erosion on riverbanks (European Commission, 2017). The dense stands can reduce access to amenities (EPPO, 2008). The presence of this species has human health impacts when people and plants come into contact. The effects of the photosensitising furanocoumarins may last for months and may be reactivated years after the initial contact (Nielsen et al., 2005; EPPO, 2009).
Reproduces by seed. First flowers 3 years post germination (Rijal et al., 2015). Generally pollinated by insects but can self-pollinate (EPPO, 2008). Two months of cold exposure are required to stimulate germination (EPPO, 2008). Large numbers of seeds are produced (Rijal et al., 2017). Seeds are dispersed over short distances by wind and over long distances by water (EPPO, 2008). Nielsen et al. (2005) report that seeds can be transported attached to animal fur or human clothing.
Pathway and vector description
Originally brought to Europe as seeds to be planted for ornamental purposes. It is on the Royal Botanic Garden Kew seed list of 1819. Spread to Ireland is most likely to occur from deliberate introduction as an ornamental plant as it is readily traded online (EPPO, 2009a) or as a seed contaminant, often of cumin seeds (Carum carvi) (Westbrooks in EPPO, 2009a). Once established the plant spreads locally by seed dispersal on the wind (EPPO, 2008) or via animals or human activity (Nielsen et al., 2005). It can be dispersed over longer distances carried along waterways (EPPO, 2008).
Mechanism of impact
Competition, Hybridisation, Poisoning/Toxicity, Other
There is currently an EU wide ban on the sale, growing and keeping of this plant (European Commission, 2017). Personnel should wear water resistant protective clothing, rubber gloves, boots, goggles and facemasks when dealing with this plant.
The general public should be educated about the identification, dangers and the ecological impact of the plant. Interested parties, for example gardeners, landowners, hikers and those using the waterways should be targeted in particular. Signs declaring the presence of Giant hogweed spp. and the possible health effects should be posted at infestations.
Movement of soil from areas of infestation should be prevented.
Machinery and equipment should be thoroughly cleaned before leaving the site.
Hard to reach areas can be cut using scythes (Nielsen et al., 2005).The Department of Agriculture and Rural Development (Northern Ireland) recommends that Heracleum mantegazzianum plants can be dug up using a sharp spade to slice diagonally through the root at least 15cm below soil level. The same method could be used for the control of H. persicum (EPPO, 2009b; Q-bank, 2017). This should be done in early spring and again in mid-summer (Nielsen et al., 2005).
Handpulling is effective for seedlings and small plants (EPPO, 2009b).
Deep ploughing (>24cm) is an effective way to control infestations on accessible land (DARD, undated; Nielsen et al., 2005). Nielsen et al. (2005) recommend first using a manual or chemical control to maximise effectiveness.
Glyphosate and triclopyr can both be used for control. Triclopyr is selective for broadleaves but is not approved for use near water. Glyphosate is not selective but certain formulations are approved for use beside water. The first application should be made in early spring with a second application before the end of May (Nielsen et al., 2005; EPPO, 2009b).
A stem injection system specially developed for Hogweed is available. An applicator gun is used to inject one stem per plant 12 inches above the root crown. This eliminates herbicide contact with non-target species and can be carried out in inclement weather (DARD, undated). However, this method puts the operative at risk of having sap sprayed back at them when they remove the needle from the stem and health and safety must be made paramount during these treatments.
Young plants just developing a rosette of leaves can be treated by rubbing with a herbicide soaked applicator (EPPO, 2009b).
The use of shading can be considered for small stands or individual plants. In spring (from April to May) the stand or plant should be covered with black polythene. Care must be taken that it is securely fixed in place and regularly checked for holes (EPPO, 2009b).
Coastal areas, hedgerows, woodlands, riverbanks, wetlands, roadsides, waste-ground, urban areas (EPPO, 2008).
Heracleum mantegazzianum and H. sosnowskyi, which are also invasives. Compared to H. mantegazzianum and H. sosnowskyi, H. persicum is smaller, has multiple stems, a mostly flat umbel and a strong aniseed-like smell (CABI, 2015). It is also similar to some native species, H. sphodylium and H. sibiricum. The natives are smaller, only 60-200cm tall, their leaves only 60cm long, and their umbels only 20cm across (Nielsen et al., 2005).
Introduced to and invasive in Denmark, Finland, Norway and Sweden (EPPO, 2009a). Also recorded in UK, Czech Republic, Estonia and Hungary (Nielsen et al., 2005).
Native to Iran, Iraq and Turkey
Records submitted to Data Centre in 2022
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How can you help
Report any sightings to the National Biodiversity Data Centre.
Do not purchase or plant in your garden.
Dispose of any garden plants or weeds responsibly.
CABI. (2015). Invasive Species Compendium. Datasheet report for Heracleum persicum (Persian hogweed). Wallingford, UK: CAB International. http://www.cabi.org/isc/datasheet/120209 Site accessed 11 September 2107.
European and Mediterranean Plant Protection Organization (EPPO). (2008). Pest risk analysis for Heracleum persicum. Risk assessment. https://gd.eppo.int/taxon/HERPE/documents Site accessed 11 September 2017.
Department of Agriculture and Rural Development (DARD). (undated). Countryside Management Publications Giant Hogweed (Heracleum mantegazzianum). http://invasivespeciesireland.com/wp-content/uploads/2016/05/giant_hogweed-DARD-updated.pdf Site accessed 6 September 2017.
European and Mediterranean Plant Protection Organization (EPPO). (2009a). Datasheets on pests recommended for regulation. Heracleum mantegazzianum, H. sosnowskyi and H. persicum. Bulletin, 39. pp 489-499. https://gd.eppo.int/taxon/HERPE/documents Site accessed 11 September 2017.
European and Mediterranean Plant Protection Organization (EPPO). (2009b). PM9/(1) National regulatory control systems Heracleum mantegazzianum, Heracleum sosnowskyi and Heracleum persicum. Bulletin, 39. pp 465-470. https://gd.eppo.int/taxon/HERPE/documents Site accessed 11 September 2017.
European Commission. (2017). Invasive Alien Species of Union Concern. European Union, Luxembourg.
Laivins M & Gavrilova G (2003) Heracleum sosnowskyi in Latvia: sociology, ecology and distribution. Latvijas Vegˆetacija 7, 45–65.
Nielsen, C.; Ravn, H.P.; Nentwig, W. and Wade, M. (eds.), (2005). The Giant Hogweed Best Practice Manual. Guidelines for the management and control of an invasive weed in Europe. Forest & Landscape Denmark, Hoersholm, 44 pp http://labgis.ibot.cas.cz/wp-content/uploads/pdf/ Site accessed 6 September 2017.
Q-bank. (2017). Heracleum persicum Desf. ex Fisch.Persian hogweed. Factsheet. http://www.q-bank.eu/Plants/Factsheets/Heracleum_persicum_EN.pdf Site accessed 11 September 2017.
Rijal, D.P.; Alm, T.; Nilsen, L.; Alsos, I.G. (2017). Giant invasive Heracleum persicum: Friend or foe of plant diversity? Ecology and Evolution, June 2017, pp- 1-15. DOI: 10.1002/ece3.3055: https://www.researchgate.net/publication/317359169 Site accessed 11 September 2017.
Rijal, D. P., Alm, T., Jahodová, Š., Stenøien, H. K., & Alsos, I. G. (2015). Reconstructing the invasion history of Heracleum persicum (Apiaceae) into Europe. Molecular Ecology, 24, 5522–5543. DOI: 10.1111/mec.13411 https://www.researchgate.net/publication/282732285 Site accessed 11 September 2017.
Westbrooks RG (1991) Heracleum mantegazzianum Sommier & Levier. Federal USDA PPQ Noxious Weed Inspection Guide. Purdue University, West Lafayette, Indiana, USA.
If contact with sap occurs, the area should be covered immediately and washed with soap and water as soon as possible. If sap gets in the eyes they should be rinsed immediately with copious amounts of water and sunglasses should be worn. High strength suncream should be worn on any affected areas for a few months following exposure. Medical attention should be sought as topical steroids may reduce the effects of the contact (Nielsen et al., 2005).