American skunk cabbage

Meet the plant

American skunk cabbage (Lysichiton americanus) has huge leathery leaves between 40cm – 1.5m in size, and bright yellow ‘flowers’ up to 45cm, which resemble those of Lords and Ladies. The yellow ‘flowers’ emerge first around April time, followed by the leaves. The central spike – the spadix – is covered in the tiny flowers which will bear seed. These seeds disperse via waterways but probably also by birds and animals.

It is found on pond margins, stream sides, bogs and wet woodlands.

It was widely planted as an ornamental species besides ponds and in bog gardens and was still on sale in Britain as recently as 2009. It has escaped from these garden locations into the wild.

Download the American skunk cabbage ID guide

Impacts

The large leaves and dense stands of the plant allow it out-compete smaller species by over shading. This can cause extensive local damage to native flora including vascular plants and mosses. American skunk cabbage can grow in shade or full-light and in a range of different soil conditions and thrives in disturbed environments.

Given the popularity of this plant in gardens and its ongoing spread into the wild, problems caused by this species are likely to increase. Although initial infestations expand slowly, once this plant takes hold it can spread more rapidly and become a more serious problem.

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American skunk cabbage management

American skunk cabbage has been found at various locations across the river catchments we work on. When we find this plant we trace it back to the source – often an ornamental pond in a garden – and start there. Ideally the source would be removed and we then work downstream to remove other plants. Usually we find skunk cabbage on smaller tributaries and ditches that feed into the main rivers so it is important to remove plants before they reach and infest the rivers.

American skunk cabbage spreads from both its underground rhizome roots and from seed production. A large seed bank can build up in the soil and remain viable for around 8-9 years – so control work is a lengthy and ongoing process in sites where the plant has become established. However, the species is slow growing and only plants of three years or older produce flowers and seeds. This means that newly infested sites can be cleared more quickly if treated before mature plants have released seed there and if upstream sources are removed.

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American skunk cabbage control

Pesticide application

Chemical control is the recommended option for treating American skunk cabbage, especially for dense stands.

However, as the plant usually grows in or beside water only suitably qualified people can undertake this work. We’ve been enabling volunteers to gain pesticide application qualifications (with the additional water module) to enable this work to be done safely.
Digging

The plant can be dug out by hand, but this must remove the main rhizomes from underground as it is thought that new plants can establish from rhizome fragments. Care is needed to collect all plant matter if digging up and material must be destroyed through burning, drying out (away from watercourses) or secure composting.

Digging can be a difficult task, due to the fact you are normally ankle deep in water and/or mud!
Cutting

The risk of spread of American skunk cabbage can be reduced in the short term by cutting the flower spike (the spadix) before it sets seed. It usually flowers in spring before leaves appear.