Rhododendron: an ecosystem perspective

Snowdonia Society volunteers have worked tirelessly for years to combat Rhododendron ponticum in Snowdonia, more specifically in Nant Gwynant.  What is so bad about this plant with beautiful pink flowers? What are the impacts of the plant itself, and of our efforts to control it?

What is Rhododendron?

Rhododendron ponticum is a large evergreen shrub with pink/ purple flowers which is native to the Mediterranean and areas of the Middle East.  It was first introduced to the UK in the 1700s. In Victorian times it became popular as an ornamental plant and was also widely planted in woodlands to provide cover for gamebirds.  In the 20th century, after a long period of apparent stability, it began spreading into the wild and has now colonised vast areas of land in the west of Britain.

Why is it a problem?

Rhododendron spreads quickly here in Snowdonia (it thrives in mild, damp climates!) and creates a dense canopy which shades the ground below, this has a number of knock on effects:

  • Rhododendron out-competes native vegetation
  • Dense canopy prevents light from reaching the ground below
  • Leaves contain compounds which acidify soil and water habitats and are toxic to many organisms
  • Animal species reliant on native plants can also be adversely affected
  • Threatens the ecology of sensitive habitats such as Atlantic oak woodlands and causes the loss of some highly sensitive species eg http://www.brc.ac.uk/plantatlas/index.php?q=node/2514
  • One of the hosts of ‘sudden oak death’ pathogen
  • Toxic to most grazing animals, making it impossible to control by grazing
  • Can take over areas of farm land, impacting economically on farming


Nant Gwynant is popular with tourists, so it is useful to look at the connections Rhododendron has with tourism.  Historically, it has been perceived positively, with coach loads of tourists coming to look at the slopes of mountains covered in purple flowers.  With tourism being so important in Snowdonia from an economic perspective, is there a conflict between tourism and Rhododendron control?

Awareness of invasive species may have increased in recent years, and large scale control projects may have helped to change the public perception of Rhododendron (try a web search of ‘Rhododendron Snowdonia’).  Groups may still come to see the slopes of Snowdonia covered in Rhododendron, but public attitudes are likely to be changing.

What do we do?

We work with Snowdonia National Park Authority (SNPA) and National Trust to identify where and how our work can best feed in to strategic control of Rhododendron.  Our volunteers brave the elements and use loppers and bow saws to tackle this invasive plant.  They are usually in the front line, cutting and clearing in advance of follow up treatment by contractors.  This follow up involves herbicide spraying of regrowth from the stumps or, more targeted application by stump-injection.

Controlling rhododendron on a landscape scale is expensive.  Repeated treatments over time are necessary to achieve high levels of control and some sites demand special techniques or equipment.  In places the work has to be done using rope access experts for example.

The control programme in Nant Gwynant, to which our volunteers contribute, has cost £millions and is far from completion.  Is that a cost or a benefit to the local economy?  Returning biodiversity, habitats, water and soils to good health sounds positive, whereas a major invasive species infestation is clearly a negative.  But you can’t have one without the other: putting the health of the environment into a system of monetary values carries the risk of some strange outcomes!



  1. (Convention of Biological Diversity, 2015 https://www.cbd.int/ecosystem/).

Comments are closed.