Short description of Lysichiton americanus, American Skunk-cabbage

Yellow flowers are produced in spring, resembling those of wild arum (lords-and-ladies) but much larger. They emit a strong odour like that of skunk. The plant has a basal rosette of leathery leaves, up to about 1 m long, which increase markedly in size as the season progresses.

Impact summary: Lysichiton americanus, American Skunk-cabbage

Its appearance and smell are thought unpleasant by some people, though others like it and continue to plant it in gardens. Reports from the New Forest and Germany suggest that it can locally out-compete native vegetation although observations in the Netherlands suggest that this can take many decades.

Habitat summary: Lysichiton americanus, American Skunk-cabbage

Its normal habitat is wet woodland, where it grows on bare or partly-vegetated nutrient-rich mud, both acid and basic, with relatively few higher or lower plant associates.

Overview table

Environment	Terrestrial
Species status	Non-Native
Native range	Subarctic America, Alberta, British Columbia, Manitoba, Saskatchewan, Arizona, California, Colorado, Idaho, Montana, Nevada, Oregon, Utah, Washington, Wyoming
Functional type	Land plant
Status in England	Non-Native
Status in Scotland	Non-Native
Status in Wales	Non-Native
Location of first record	v.c.17 (nr Haslemere)
Date of first record	1947

Origin

Native of western North America, from northern California to southern Alaska. It is sometimes called western skunk cabbage to distinguish it from another member of the Arum family that occurs in eastern North America. The closely related Asian skunk-cabbage Lysichiton camtschatcensis (with a white spadix) occurs in eastern Asia and is also naturalised in GB and grows with it in a few localities.

First Record

It was introduced in 1901 and first reported as an escape in 1947, near Haslemere in Surrey.

Pathway and Method

The normal pathway is horticulture. It has the Royal Horticultural Award of Garden Merit, and was available from more than 40 suppliers in 2009. Skunk cabbage is widely planted in bog gardens, from which it either escapes or merely spreads over muddy ground if the garden is abandoned.

Species Status

Widespread (c.400 hectads) but not generally common. It is apparently increasing in lowland and semi-upland Britain except for the English Midlands and drier parts of Eastern England.

Dispersal Mechanisms

A long-lived perennial, with thick fleshy rhizomes, which may be broken and dispersed by machinery or by water during floods. Short-distance dispersal is by seed. In its native range, berries are dispersed by birds, squirrels and bears. Berries can be transported downstream. In GB, it spreads over several tens of metres from the point of introduction, to form dense monospecific stands. Longer-distance dispersal (up to 5km) from large colonies has also been observed on a few rivers in northern England (e.g. River Nidd).

Reproduction

Male, female and sometimes hermaphrodite flowers occur in the same inflorescence. Pollination in North America is by beetles. The fruits are green berries. They are produced freely in GB, ripening in July and early August.

Known Predators/Herbivores

In GB gardens, skunk cabbage is generally free of diseases and does not have predators. This is presumably true of plants that have escaped into the wild.

Resistant Stages

Seed survival up to six years is signified by Klingenstein & Alberternst (2006). However, an American horticultural website suggested that seeds should be sown quickly, so they may more often be short-lived, forming a transient seed bank like those of the native GB lords-and-ladies Arum maculatum.

Habitat Occupied in GB

It occurs in swamp woodland and carr, and on muddy pond margins and stream and riversides, typically on rich fertile mud, which may be acid, neutral or basic. In northern England its habitat is very similar to that of Caltha palustris, Carex remotaand Chrysosplenium oppositifolium with which it often grows.

There is a concentration of records in southeast England, most notably in Hampshire, Surrey and Sussex. Outside these strongly horticultural counties, it appears to have a rather northern and western lowland distribution extending from the far western tip of Cornwall to Inverness in the north of Scotland. It is virtually absent from the drier past of Eastern England.

Environmental Impact

Sanderson (2013) reported a significant decrease in numbers of associates within two riverine woodlands invaded by Lysichiton americanus in the New Forest, Hampshire, UK. Reports of it having similar adverse impacts on swamp communities in Germany require confirmation for naturally-spreading populations, as at the most affected site it had been deliberately planted in many different locations by a gardener.

Health and Social Impact

None known.

Economic Impact

None known.

Identification

Flora of North America

Biology, ecology, spread, vectors

Klingenstein F. & Alberternst B. (2006) NOBANIS - Invasive Alien Species Fact Sheet - Lysichiton americanus. - From: Online Database of the North European and Baltic Network on Invasive Alien Species - NOBANIS http:www.nobanis.orgfilesfactsheetsLysichiton%20americanus.pdf, Date of access 21052009.

Willson, M.F. & Hennon, P.E. (1997) The natural history of western skunk cabbage (Lysichiton americanum) in southeast Alaska. Canadian Journal of Botany, 75, 1022-1025.

Management and impact

Klingenstein & Alberternst (2006) - see above

Sanderson, N.A. 2013. Research on the impact of American Skunk Cabbage Lysichiton americanus on native vegetation. Report commissioned by Hampshire & Isle of Wight Wildlife Trust on behalf of The New Forest Non-Native Plants Project.

General

Klingenstein & Alberternst (2006) - see above