Heracleum sosnowskyi | Sosnowskyi's hogweed
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].
Invasive species - risk of Medium Impact
Introduction pathways - 1
Escape from Confinement
Introduction pathways subclass - 1
Introduction pathways - 2
Introduction pathways subclass - 2
Vehicles, Other means of transport
NAPRA Ireland risk assessed
Large monocarpic biennial or perennial herb. Can grow up to 3m (CABI, 2009). Usually has single stem which is ridged, slightly hairy and often has purple blotches (CABI, 2009). Leaves can be 3m long and have a slightly hairy underside (CABI, 2009). Three pairs of serrate leaflets. The leaf margins have short rounded teeth (Kabuce & Priede, 2010). white or pinkish flowers are held on umbels (umbrella-shaped heads) that can be 50cm across (CABI, 2009). Generally flowers from June to August (CABI, 2009). 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 sosnowskyi reduces biodiversity in the varied habitats it infests. Its dense stands, height, large leaves and early germination and fast growth (CABI, 2009) outshade smaller native plants creating a 'giant hogweed landscape' (Nielsen et al., 2005). H. sosnowskyi is estimated to absorb 80% of the available light (Nielsen et al., 2005) allowing it to out-compete most plant species other than trees (EPPO, 2008). Heracleum spp. hybridize readily (EPPO, 2009a) and this is a possibility with H. sosnowskyi. Dieback during the autumn leaves bare soil exposed to erosion on riverbanks (European Commission, 2017, CABI, 2009). The dense stands can reduce access to amenities such as rivers, lakes and forests (EPPO, 2008) and may be a road safety issue due to reduced visibility (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).
Solely seed propagated with seeds remaining in the seedbank for 5 years (Klima & Synowiec, 2016). Most seeds germinate within the first season (Klima & Synowiec, 2016) after cold exposure of less than 2 months (EPPO, 2009a). Generally insect pollinated but can self-pollinate (EPPO, 2008). Seeds are dispersed close to the mother plant by wind or over longer distances carried on waterways (CABI, 2009). Seeds can also be transported by animals in their coats (Nielsen et al., 2005) and by human activity (EPPO, 2008).
Pathway and vector description
Was introduced to Russia as a forage crop in the 1940's (Nielsen et al., 2005; EPPO, 2009a). It was introduced to Iceland as an ornamental but once it became invasive it was eradicated (CABI, 2009). In Estonia it was trialled as a silage crop and for honey production (CABI, 2009). Its use as a silage crop was abandoned due to tainting of the milk and meat with an aniseed flavour as well as the health impacts on humans and livestock (CABI, 2009). Spread from countries where it is established to new areas within the EU is most likely as a contaminant on car or machinery tyres, on footwear or when soil is traded as a commodity with the EU (CABI, 2009; EPPO, 2008). Seed production will likely only contribute to local spread (EPPO, 2008).
Mechanism of impact
Competition, Hybridisation, Poisoning/Toxicity
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).
Root cutting with a sharp spade 15cm below soil level is an extremely effective method and complete control can be achieved when plants are less than 7 years old (Klima & Syniwiec, 2016). 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). Klima & Synowiec (2016) recommend spraying 3 times in a season to prevent flowering.
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).
Roadsides, railways, fields, wasteground, grassland, parks riverbanks, canal-sides, forest margins, wetlands.
Heracleum mantegazzianum. H. mantegazzianum can be distinguished as the rays of the umbel have both long and short hairs. H. sosnowskyi rays have only short hairs. H. mantegazzianum leaf margins are sawtoothed but have short rounded tooth margins in H. sosnowskyi.
H. persicum. H. persicum is smaller, has multiple stems, a mostly flat umbel and a strong aniseed-like-smell and the stem is often purple (CABI, 2009).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). They also have greyish hairy leaves (CABI, 2009).
Introduced in Belarus, Denmark, Estonia, Finland, Hungary, Latvia, Lithuania, Poland, Russia and Ukraine. It is not considered invasive in Denmark and Finland (CABI, 2009).
Native to the Caucasus, Transcaucasia and north-eastern Turkey (European Commission, 2017).
Records submitted to Data Centre in 2021
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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.
Do not purchase soil from infested countries.
CABI. (2009). Invasive Species Compendium. Datasheet report for Heracleum sosnowskyi (Sosnowskyi's hogweed). Wallingford, UK: CAB International. http://www.cabi.org Site accessed 11 September 2107.
European and Mediterranean Plant Protection Organization (EPPO). (2008). Pest risk analysis for Heracleum sosnowskyi. Risk assessment. https://gd.eppo.int/taxon/HERSO/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.
Kabuce, N. and Priede, N. (2010): NOBANIS – Invasive Alien Species Fact Sheet – Heracleum sosnowskyi. – From: Online Database of the European Network on Invasive Alien Species – NOBANIS www.nobanis.org, Site accessed 11 September 2017.
Klima, K & Synowiec, A. (2016). Field emergence and the long-term efficacy of control of Heracleum sosnowskyi plants of different ages in southern Poland. Weed Research, July 2016. DOI: 10.1111/wre.12214
Nielsen, C; Ravn, HP; 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.