Dec 08 2020

Rhododendron zapping trial in South East

Thanks to Jim Smith-Wright, South East Outreach adviser, for writing this wonderful article.


Rhododendron is a massive problem in the South East, invading many of our most precious ancient woodlands and other habitats and denuding them of most of their value for wildlife. Controlling or removing the plant is almost as problematic, with most established methods being expensive, polluting, and/or causing further damage to the habitat, particularly ancient woodland soils.


So we’re very keen to find new approaches; over the last year we have been trialling a variety of different techniques, old and new, at Runtington Wood, a landowner’s ancient woodland near Heathfield in East Sussex. Our South East Outreach team have been helping to restore this site for several years, where rhododendron has until recently formed a dense jungle across most of the woodland. An invasive species management plan has been drawn up by our consultants, Maydencroft, with the site divided up into different plots, and each plot allocated a different treatment control scheme.


The most novel and exciting of these is a new technology called Rootwave, which basically zaps weeds with the vegetable equivalent of a cattle prod(!). An electric current is generated by a vehicle-mounted generator and then passed through a lance into the plant and down into the roots, killing all of the live tissue that it passes through in the process, before dissipating harmlessly upon reaching the soil.


The technology is tried and tested on smaller, non-woody ‘weeds’, but to date there has been very little use on woody shrubs such as rhododendron. Jim approached Rootwave’s Commercial Manager Stephen Jelley, with a proposal to include their technology in our trial, and he was so keen to be involved that he offered to do a trial treatment for us for free!


The photos/videos show the trial in action, with Stephen zapping the regrowth on a number of plants which were cut down to the base last year with a chainsaw, to give the best possible chance of killing them with one treatment (conventional treatment with chemicals usually takes a number of years to be successful). The initial result was certainly impressive; the stools fizzed and popped, gave off great gusts of steam, sparks, and in some cases even caught fire(!), before finally wilting away. However time will tell if the whole stools have actually been killed outright.


Monitoring began on the site last year to record the response of the woodland’s wildlife to the removal of the rhododendron. This includes fixed point photography and fixed point audio recording, carried out by our amazing volunteer, Hilary Hinks.


“It’s great to have the opportunity to get out into a woodland and take photos and short audio recordings.  Little “snapshots in time”, of what it looks and sounds like, taken from the same locations a few times a year.  These build up into a record of how the wood is changing over time, interesting on many levels, but particularly when we are using them to help evaluate the effectiveness of new techniques to rid the wood of invasive species such as rhododendron.”


We will continue the monitoring for a number of years in order to evaluate the relative successes/failures of this and the various other techniques.


At present the potential for the technology is fairly limited, particularly in terms of treating large areas cost-effectively, however new options are currently being developed which will include a backpack-based option for greater mobility, and a larger vehicle-mounted plate option for treatment of larger plants/clumps.

1 Comment
  • KeithLelliott

    Wow – will it take out wild clematis. There’s enough at Langley Vale to keep us volunteers occupied full time clearing the stock fences with secateurs and loppers.

    December 8, 2020 at 2:30 pm

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