Rhododendron Season Begins Again!

We all associate autumn and winter with woodland management- as the birds finish breeding and temperatures cool, we start our programme of woodland coppicing and thinning, and the removal of invading trees and scrub on our valuable open habitats such as rhos pasture, meadows and bogs. Felling season is here again.

Rhody bashing Castle Woods by L Wilberforce

Rhody bashing Castle Woods by L Wilberforce

However, the change of season also brings with it the start of efforts to control our most time-consuming invasive non-native species (INNS), Rhododendron ponticum.

Rhododendron ponticum (and its hybrids) can be shrub-like in form or given the right conditions and time, a small tree. It is common in parks, gardens and estates, thanks to its attractive purple flowers, but has spread widely into the natural environment. It is native to parts of Iberia, eastern Europe and western Asia. It was first introduced to the UK from Spain in 1763, with further introductions ever since.

By 1894 it was already recorded in the wild and has since spread widely. It particularly favours wooded areas, open habitats on acid soils, and areas where humidity levels are high- describing many of our habitats (and nature reserves) in west Wales to perfection.

So what is the problem?

  • Rhododendron spreads voraciously by several means- it is still planted as an attractive garden plant and dumped garden waste can be a source of spread to the wild. Once established, it spreads by seed and suckers and even cut limbs can re-root if left on the ground.
  • Its dense foliage shades out our native ground flora, excludes our native shrubs, and even hinders tree regeneration (oak for example needs high light levels to regenerate).
  • Woodlands infested with Rhododendon have been shown to have significantly lower breeding bird populations, including of woodland specialist species such as pied flycatcher that are so important in Wales.
  • It can totally out-compete valuable open habitats such as the montane flora of Snowndonia, where the National Park has estimated a cost of £10M if it is to be controlled effectively.
  • It even produces chemicals that suppress the growth of seedlings of other species; this effect even persists after the Rhododendron has been removed. It also hosts Phytophthera diseases that can be damaging to our native species.
Rhododendron flowers © Andreas Praefcke, Creative Commons Attribution-Share Alike 3.0

Rhododendron flowers © Andreas Praefcke, Creative Commons Attribution-Share Alike 3.0

Rhododendon occurs on many of our nature reserves across south west Wales. In Ceredigion, efforts have been made to cut and treat the plant in Old Warren Hill and Coed Penglanowen. On Gower, large areas of the shrub have been removed from Gelli Hir nature reserve by staff up to their knees in the wet woodland’s mud. In Carmarthenshire, the shrub is gradually being eradicated from the steep slopes of Castle Woods nature reserve. It also occurs in the middle of the tussocky wet grassland of Cors Pum Heol- a very tricky location in which to control it.

We are fortunate that much of this work has been supported financially in recent years by Forestry Commission Wales’s Better Woodlands for Wales grant scheme. Curbing the spread of this shrub will gradually lead to the restoration of native species in areas it once dominated. It still takes a lot of elbow grease to manage though- if you fancy partaking in a little ‘Rhododendron bashing’, get in touch with your local Wildlife Trust Officer.