Taxonomy

Heracleum mantegazzianum | Giant Hogweed | Feabhrán capaill

Distribution

Status

Conservation status

Least Concern

Legal status

Third Schedule listed species under Regulations 49 & 50 in the European Communities (Birds and Natural Habitats) Regulations 2011. (Note: Regulation 50 not yet enacted).

Listed as a schedule 9 species under Articles 15 & 15A of the Wildlife Order (Northern Ireland) 1985 (Article 15A not yet enacted).

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].

First reported in the wild

pre-1866

Invasiveness

Invasive species - risk of High Impact

Irish status

Established

Introduction pathways - 1

Escape from Confinement

Introduction pathways subclass - 1

Ornamental purpose

Invasive score

19

NAPRA Ireland risk assessed

No

Species Biology

Identification

Biennial or perennial monocarpic herb wit a pale yellow root. Single stem up to 10cm thick at the base and up to 5m tall, with purple patches. Flowers white (rarely pinkish), in umbrells up to 80cm across (Tiley et al., 1996). May be confused with Angelica sylvestris, but this species has a much thinner stem and is rarely more than 1m tall.

Ecology

Can form extensive stands and as cover increases can decrease the number of vascular plant species per unit area (Thiele & Otte, 2007). Can cause erosion of river banks when the plant dies back during winter exposing bare soil (Caffrey, 1999) and soil influx into rivers can render gravel substrates unsuitable for salmonid spawning (Caffrey, 1999). May impact on human health due as compounds in the sap can cause phytophotodermatitis within 24-48 hours after exposure, with symptoms including: mild to severe erythematours reactions (red colouring of the skin); blistering of the skin; and hyper-pigmentation of burned parts of the skin for months or years (Thiel & Otte, 2007).

Habitat

Mires, bogs & fens; Grasslands and landscapes dominated by forbs, mosses or lichens; Woodland, forest and other wooded land; Constructed, industrial or other artificial habitats; Regularly or recently cultivated agricultural, horticultural or domestic habitat

Reproduction

Flowers, generally after 3 years, producing large amounts of seed, estimated with estimates ranging from 5,000-29,000 seeds per plant, though the potential seed production may be as high as 100,000 per plant (Tiley et al., 1996).

Pathway and vector description

Popular Victorian garden 'curiosity', it was introduced to Britain and then Ireland in the 19th century (Reynolds, 2002). First noted escape from cultivation was in 1902-1903 in Dublin (Reynolds, 2002).

Mechanism of impact

Competition

Management approach

There is currently an EU wide ban on the sale, growing and keeping of this plant (European Commission, 2017). Protective clothing, facemasks and goggles, rubber boots and gloves must be worn by personnel involved in the control of this species (DARD, undated).

Public awareness

Education of the general public in identification of Heracleum mantegazzianum as well as its human health and ecological impacts would assist in early detection and reduce the number of contacts with the plants. Posters, leaflets, radio and online information would all be valuable. Signs declaring the presence of Giant hogweed and its possible health effects should be posted at infestations.

Manual

Hard to reach areas can be cut using scythes (Nielsen et al., 2005). H. mantegazzianum are monocarpic and usually flower at 3 or 4 years (Caffrey, 1999). Only cutting the flowering plants (during mid-flowering) will eradicate seed production and the plants will gradually shade each other out (Nielsen et al., 2005). This is much less labour intensive than other manual methods but should be effective within a few years.

Plants can be dug up using a sharp spade to slice diagonally through the root at least 15cm below soil level (DARD, undated). This should be done in early spring and again in mid summer (Nielsen et al., 2005).

Mechanical

Deep ploughing (>24cm) is an effective way to control infestations on accessible land (DARD, undated; Nielsen et al., 2005). Nielsen et al. (2005) recommend using a manual or chemical control first to maximise effectiveness.

Chemical

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 some 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). Eradication will require treatment for 4-5 years (DARD, undated).

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).

Environmental

Cattle and sheep readily eat H. mantegazzianum and grazing will gradually weaken and kill the plants (Nielsen et al., 2005). Stock should be monitored for signs of photosensitisation and digestive problems, which can result from the consumption of the furanocoumarins in the plants (DARD, undated). Dairy animals should not be used as the milk will have an unpleasant odour (DARD, undated). This method can eradicate an infestation within 5-10 years (DARD, undated).

Broad environment

Terrestrial

Habitat description

Found on riversides, roadsides, waste ground and former cultivated fields.

Species group

Plant

Native region

Temperate Asia

Similar species

Heracleum sosnowskyi, Heracleum persicum

Distribution

World distribution(GBIF)

Irish distribution

Established - Widespread. Locally abundant, naturalised and invasive (Reynolds, 2002), found along river banks and waste ground, favours damp ground (Reynolds, 2002). May occur initially as a single plant but due to large volumes of seeds produced can rapidly spread within an area (Tiley et al., 1996).

Native distribution

Native to the Caucasus (Tiley et al., 1996), the area between the Black and Caspian seas.

Temporal change

Date of first record category

Pre-1900

Fifty year date category

Unknown

Records submitted to Data Centre in 2017

The following map is interactive. If you would prefer to view it full screen then click here.

How can you help

Report any sightings to the National Biodiversity Data Centre

Further information

Delivering Alien Invasive Species In Europe (DAISIE) project list this as one of the 100 Worst Invaders in Europe.

Control and management guidance documents listed here but please note that advice should be sought on best control options for infestations in Ireland and more locally and especially in the use of herbicides.

Nielsen, C., H.P. Ravn, W. Nentwig and M. Wade (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. Available from: http://bit.ly/2vJEoPN [Accessed: 08/08/2017]

Giant hogweed (Heracleum mantegazzianum). Countryside Management Publications. Department of Agriculture and Rural Affairs. Available online: http://invasivespeciesireland.com/wp-content/uploads/2016/05/giant_hogweed-DARD-updated.pdf [Accessed: 08/08/2017]

References

Publications

Caffrey, J. M., & Madsen, J. D. (2001). The management of giant hogweed in an Irish river catchment. Journal of Aquatic Plant Management, 39, 28-33.

Caffrey, J.M. (1999) Phenology and long-term control of Heracleum mantegazzianum. Hydrobiologia 415, 223–228.

Department of Agriculture and Rural Development. (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 Commission. (2017). Invasive Alien Species of Union Concern. European Union, Luxembourg.


Nielsen, C., H.P. Ravn, W. Nentwig and M. Wade (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.

Reynolds, S.C.P. (2002) A catalogue of alien plants in Ireland. National Botanic Gardens. Glasnevin, Dublin.

Thiele, J., & Otte, A. (2007). Impact of Heracleum mantegazzianum on invaded vegetation and human activities. In: Pysek P, Cock MJW, Nentwig W, Ravn HP (eds., 2007) Ecology and Management of Giant Hogweed (Heracleum mantegazzianum). CAB International, pp 144-156.

Tiley, G. E. D., Dodd, F. S., & Wade, P. M. (1996). Heracleum mantegazzianum Sommier & Levier. Journal of Ecology, 297-319.

Global Invasive Species Database

Invasive Species Ireland

DAISIE Factsheet

CABI Datasheet

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