Taxonomy

Lysichiton americanus | American Skunk-cabbage | Geathar buí

Distribution

Status

Conservation status

Not Assessed

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].

Native status

Non-native

First reported in the wild

1930

Invasiveness

Invasive species - risk of Medium Impact

Irish status

Established

Introduction pathways - 1

Escape from Confinement

Introduction pathways subclass - 1

Ornamental purpose

Invasive score

15

NAPRA Ireland risk assessed

Yes. View full risk assessment from: http://nonnativespecies.ie/risk-assessments/ 

The conclusion response of the overall risk of this species  in Ireland was of MINOR with a Medium level of confidence. The summary conclusion states:

'The horticultural trade is the primary factor in the entry of this species to new areas and L. americanus has a long history of cultivation and introduction, though it has never been a particularly popular species and is not grown on a large scale (CABI, 2014). Both the size of the plant, its habitat and the smell of the flowers restrict its popularity for small gardens (CABI, 2014). Lysichiton americanus is most likely used in large scale gardens and ponds where it can “take care of itself” (CABI, 2014).

Lysichiton americanus is already established in Ireland, but is not widespread. Regionally it is very abundant in sites where populations have established, such as Kerry (Reynolds, 2002). It is known to have taken decades to settle and dominate even small sites in the Netherlands where it took about 50 years to establish a small but viable and locally spreading population (CABI, 2014). Establishment and spread of new populations in Ireland is likely to be very slow and restricted by a limited availability of wet habitat.

No economic, social or environmental impacts are reported in the species native range. With the exception of costs related to control/eradication measures, the economic and social impacts of L. americanus in its introduced range are negligible. Known environmental impacts are largely confined to an invasive population of the species in Germany. It can, however, be expected that the reduction in biodiversity and displacing effects attributed to the presence of L. americanus in the Taunus area of Germany, would also manifest themselves if the species establishes dense stands in vulnerable Irish habitat.'

Species Biology

Identification

A large leaved  perennial herb up to 1.5 metre in height (Booy et al., 2015) . It has a basal rosette of green leathery leaves that are flat or tapered at the base, can grow up to about 1 metre long, are oval/oblong shaped and are rolled when young. The leaves have an unpleasant 'skunk' smell when crushed.

It has a large yellow sheath that surrounds a spike of greenish flowers, is foul smelling and appears as leaves are emerging from the soil (Booy et al., 2015)

The large size,  smell likened to 'rotten flesh' and the yellow sheath of American skunk cabbage are the distinguishing features.

It spreads by rhizomes and seeds.

The plant dies back in winter.

Ecology

Klingenstein and Alberternst  (2010) note that 'in its natural and introduced range Lysichiton americanus grows in the transition zone of terrestrial, semi-aquatic and aquatic habitats like swamps, wet woods and shrubs, along streams and riverbanks, lakesides, ponds, in boggy and other wet areas. As long as the site is wet, it has no specific soil requirements... and can grow in shade or full light. It is hardy to at least -15°C and grows from 0-1400 m altitude.'

It is a long lived species (~80 years) (Albertternst et al., 2009) allowing it to form dense, interminable patches, excluding other vegetation (Sanderson, 2013).

Habitat

Mires, bogs & fens

Reproduction

Reproduces by seeds (Preston et al., 2004), each plant producing 700-800 seeds (Albertternst et al., 2009).

Note: it also spreads by rhizomes.

Pathway and vector description

Occasional garden escape, it was previously a more popular garden plant though deliberately planted at Woodland Bog, Co Offaly (Doyle & Duckett, 1985). Spread in Ireland is likely to be by natural means, once the species has become naturalised which may require an extended period of time, plants at Woodland Bog did not seed for many years after introduction (Doyle & Duckett, 1985).

Mechanism of impact

Competition

Broad environment

Terrestrial

Habitat description

Favours damp habitats e.g. wet woodlands, marshes, lake and river banks (Reynolds, 2002).

Species group

Plant

Native region

North America

Similar species

When NOT in flower, it may be confused with the native Water plantain (Alisma plantago) which is fairly common in slow flowing habitats. The distinguishing features of Water plantain is that it's leaves are rounded at the base and do not have an unpleasent 'skunk' smell when crushed. The flower is very different being 3 white to lilac coloured petals with a yellow blotch towards the centre. 

It is most similar in appearance to its relative the Asian skunk cabbage (Lysichiton camtschatcensis) but the main distinguishing feature to tell them apart is that the American skunk cabbage has a yellow sheath around the flower spike  whereas the Asian skunk cabbage has a white sheath. Asian skunk cabbage is scentless.

Asian skunk cabbage is not known to occur in the wild in Ireland so probability of confusion with the regulated American skunk cabbage is very slim.


Distribution

World distribution(GBIF)

Irish distribution

Established - Widespread but occasional, locally abundant.

Native distribution

Native to western North America (Preston et al., 2004).

Temporal change

Date of first record category

1921-1930

Fifty year date category

1901-1950

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. Do not plant in the wild or in gardens where it may escape or seed into the wild.

Further information

Management information for this species in Ireland has not been developed yet.  

CABI 2014, note the following general information on control of this plant:

Physical/mechanical control

Available control reports all describe removal by hand as the method of choice. In doing so one has to take care that the underground corm is removed. This is often not easy because it may be deep in the swamp (over 30 cm) and hard to remove. After initial action several years of inspection and seedling removal are necessary.

Chemical control

No reports on control of invasive Lysichiton refer to chemical control. It is likely that chemical control would be efficacious, but equally it should be expected that chemical control would do considerable collateral damage to the sensitive aquatic environment. It is likely that chemical control has not been tried for this reason.'

CABI Datasheet

References

Publications

Albertternst, B., Buhozler, S., Duenas, M. A., Fried, G., Newman, J., Schrader, G., Triest, L. & van Valkenburg, J. (2009). Report of a Pest Risk Analysis: Lysichiton americanus Hultén and H. St. John. European and Mediterranean Plant Protection Organisation

Booy, O., Wade, M. & Roy, H. (2015) A Field Guide to Invasive Plants & Animals in Britain. Bloomsbury.

CABI. 2014. Lysichiton americanus (American skunk cabbage) [original text by Ton Rotteveel] [Online]. Invasive Species Compendium: Wallingford, UK: CAB International. Available: www.cabi.org/isc [Accessed 02/12/2016].

Doyle, G. J., & Duckett, J. G. (1985). The Occurrence of Lysichiton americanus Hultén & St. John on Woodfield Bog, County Offaly (H18). The Irish Naturalists' Journal, 536-538.

Klingenstein F. and Alberternst B. (2010): NOBANIS – Invasive Alien Species Fact Sheet – Lysichiton americanus. – From: Online Database of the European Network on Invasive Alien Species - NOBANIS www.nobanis.org, Date of access 02/12/2016.

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

Preston, C.D., Pearman, D. A. & Dines, T. D. (2002). New atlas of the British and Irish flora. An atlas of the vascular plants of Britain, Ireland, the Isle of Man and the Channel Islands, Oxford University Press.

Sanderson, N. (2013). New Forest Non-Native Plants Project research on the impact of skunk cabbage Lysichiton americanus on native vegetation. Report for Hampshire & Isle of Wight Wildlife Trust.

Stace, C. (1997). New Flora of the British Isles 2nd Edition. Cambridge University Press, Cambridge.

CABI Datasheet

Images