Skip to main content

Invasive alien species are one of the main direct drivers of biodiversity loss worldwide.

In Scotland, significant efforts are being made by Forestry Land Scotland (FLS) to control invasive species, such as rhododendron, on the forests and land it manages.

FLS is also tackling other invasive plant species including Salal (Gaultheria shallon) and American Skunk Cabbage (Lysichiton americanus) both of which are a particular menace in Western Scotland, Dumfries & Galloway, and the South of Scotland.

An evergreen member of the heather family of plants, Gaultheria was originally brought from North America, cultivated in the 1800s and planted as cover for gamebirds such as grouse.

In recent years it has become highly invasive, especially in Argyll and west Scotland on sites formally occupied by rhododendron, where it regenerates rapidly after clearance.

American skunk cabbage, widely planted as an ornamental water plant, is most often found on pond margins, stream sides, bogs and in wet woodlands.

Tall with huge leathery leaves and bright yellow 'flowers' resembling those of a British native plant – Cuckoo-pint or Lords and Ladies – it gradually escaped from gardens and into the wild and has now become problematic.

Perhaps the best-known non-native invasive plant is Rhododendron, which reduces the biodiversity value and quality of soils it grows in.

Notoriously difficult to eradicate successfully, it is toxic to many species and research has shown it reduces the number of earthworms in the soil. It physically reduces the presence of native ground flora and interrupts natural regeneration of woodland.

FLS has been working for over 25 years to turn back the relentless tide of rhododendron that is smothering much of the west coast and threatening unique rainforest habitat, and is tackling it in number of ways:

  • Technology: FLS is using drones to help map the best areas to focus rhododendron removal efforts in a bid to give breathing room to Scotland’s rainforests.
  • Rainforest restoration work: to identify areas where rhododendron is impacting on habitat quality and then control it via the careful application of approved herbicides. New, more effective stem-injection techniques have halved the time required to treat an area and, with a 90-100% success rate, significantly reduce the need for re-treatments.
  • Hand pulling of small plants in the case of rhododendron. FLS is also working to improve its survey of remote areas to identify so-called “pioneer bushes” before they become established and more problematic to tackle. 
  • Encouraging a landscape scale approach: as in Glen Creran, where it has been eliminated thanks to a four-year community project led by the Argyll and the Isles Coast and Countryside Trust, but this takes immense effort and the good will and support of the local community.  

Skunk Cabbage and Gaultheria are similarly being controlled through the application of approved herbicides that do not pose a risk to other plant species or animals.

FLS also support the efforts of other organisations to control species such as the North American Signal Crayfish; the American mink, which is a serious threat to native water vole; and grey squirrel, which threatens the UKs native red squirrel.

FLS is playing its part in helping to control the march of grey squirrels by installing artificial pine marten boxes in FLS managed forests to boost the pine marten population in particularly sensitive areas. Pine Martens predate on grey squirrels, but reds and pine martens appear to happily coexist.

Earlier this year, Forestry and Land Scotland was allocated £1.3m of Scottish Government funding to help boost activity to save Scotland’s Rainforest.

As well as reinforcing FLS’s rhododendron removal work and deer management, the funding will help FLS develop a long-term, strategic approach to safeguard this unique habitat, a third of which is managed by FLS.

Speaking about non-native and invasive species control, FLS Environment Manager, Colin Edwards, said;

“Many of these alien species are threatening Scotland’s biodiversity including some of our unique and most precious rainforests.

“These invasive plant and animal species are also notoriously difficult to eradicate and achieving lasting success requires a co-ordinated approach, working with like-minded land managers, often at a landscape scale.

“There are things that everyone can do to help, for example by participating in volunteer schemes that support landscape scale control of invasive plants and animals.”

In Fife for example, landowners and people with gardens are being urged to help control grey squirrels via live trapping, to help halt the northward march of squirrel pox, a disease that is carried by greys and kills reds. The call comes after a red squirrel that had died from the squirrel pox was found on the northern edge of Dunfermline early last month.

Gardeners can help by being mindful of what they plant and checking what they already have growing in the garden in case they have a problem plant that is on the banned list. While plants from overseas have enriched the UK’s gardens, a small number have become highly invasive in the UK, threatening natural habitats and native species. RHS (Royal Horticultural Society) publishes a useful checklist.


Notes to editors

  1. Forestry and Land Scotland (FLS) manages forests and land owned by Scottish Ministers in a way that supports and enables economically sustainable forestry; conserves and enhances the environment; delivers benefits for people and nature; and supports Scottish Ministers in their stewardship of Scotland's national forests and land.

  2. |

  3. Media enquiries to Paul Munro, Media Manager, Forestry and Land Scotland Media Office 07785 527590 or