The first thoughts that may spring to mind when you hear “rhododendron” is a pretty garden shrub. However, one species, Rhododendron ponticum – recognisable for its purple flowers – causes a lot of problems for our native plants. Rhododendron ponticum is an invasive non-native evergreen shrub that contributes to biodiversity loss in Scotland.  

What’s so bad about rhododendron?

Rhododendron ponticum (hereafter referred to as rhododendron) was first introduced to Britain in the 18th century as a garden plant. Seeds are light and dispersed by wind or water so the plants can spread quickly. Shrubs can grow up to 8 m (25 feet), towering over other species and blocking out light with their thick leafy canopy. Rhododendron will out-compete many native trees and shrubs and can harbour plant diseases. This leads to reduced biodiversity and can have additional negative implications for some rural livelihoods, for example if rhododendron, poisonous to mammals, invades grazing land.

Rhododendron in Argyll

We are fortunate to have internationally important habitats here in Argyll, such as peatland and Atlantic woodland. Rhododendron can invade peatlands and prevent the vital accumulation of organic matter which forms peat. It also impacts our native woodlands such as oak, willow and birch woods, which support a rich community of rare species many of which are of global significance.  These habitats have been identified as a top priority for complete rhododendron removal to conserve them for future generations.

Rhododendron ponticum on peatland on Islay

What can be done?

As you can imagine, eradication of such a widespread, pernicious plant is difficult. Young bushes can be pulled out, but more force is required for mature rhododendron. Mature shrubs can be manually cut with chainsaws and then the stumps are treated with herbicide. In the right site conditions, rhododendron can be flailed (mulched) mechanically with a special, tracked vehicle. The method used will depend on several variables such as access and how established the rhododendron is.

Due to the scale, persistence and ease of spread of rhododendron, control will only be successful if work is planned at a landscape level, with thought given to long term management and control.

Manual removal of rhododendron... ...can be labour intensive

Working together

Two of our projects involve partnership working to ensure successful landscape scale control of rhododendron. For both projects, communities are key partners. Firstly, our Glen Creran project aims to control rhododendron in the Glen’s Atlantic woodlands. Secondly, the CANN project team on Islay are managing the removal of rhododendron on the peatland sites, where rhododendron is damaging areas of blanket bog and scrub woodland and the species supported by these habitats. They will work with landowners to ensure the peatlands aren’t re-invaded once the project ends.

Keep an eye out for our next blogs which will go in to more detail about rhododendron management and control at our two project sites.