Rhododendron: Blacklisted?

Dr Trevor Dines
Plantlife Botanical Specialist





Sitting on a hillside above the village of Beddgelert and surrounded by the peaks of Snowdonia, I feel like I should actually be in the wilds of northern China. All around me are billowing mounds of Rhododendron, their fat buds ready to explode and paint the landscape purple. This is proper Rhododendron forest; thick, dense, dark and completely silent. This is how Rhododendron kills – the canopy of evergreen leaves blocks sunlight so that nothing can grow beneath it and chemicals from its fallen leaves inhibit the germination of seeds. Once Rhododendron has taken hold, eradication is costly and time-consuming.

Only it’s not actually Rhododendron ponticum, a rather weak and tender species from southern Europe, we’re talking about, but an invader of our own making.

The view in question. © Dr Trevor Dines

All invasive Rhododendron found in the wild throughout Britain is a hybrid created by Victorian gardeners. By crossing R. ponticum with more robust North American species they created a highly invasive newcomer. Perhaps in allusion to its power to spread, it has now been named R. x superponticum.

But what’s in a name? The European Parliament is currently drawing up plans to blacklist the most invasive non-native species. This new legislation will ban the possession, transport, selling or growing of species deemed to be of "Union Concern". This is a major step forward in co-ordinated efforts to tackle the spread of the worst offenders, but alarm has been raised in some quarters around the lack of clarity over which species will be included. It’s been suggested, for example, that 300 garden Rhododendrons could banned as they can trace their parentage back to Rhododendron ponticum.

It is highly unlikely that R. ponticum will be included. Since R. ponticum is native to Spain and Portugal it can’t be listed as a concern for the whole Union; only the most invasive non-native species across Europe can be included. Instead, it can only be placed on a Regional list for those countries where it’s a problem and this limits what can be done about controlling it under the new legislation.

We are a long way from deciding what goes onto the list. The regulations being voted on now won’t come into force until 1st January 2015 and there will be a further 1.5 years to put the measures in place. Until then, we have time to develop selection criteria and propose which species should be listed. Any species proposed will have to be put through formal Risk Assessment before making it onto the list, a process we’ll all be involved with.

As for the hybrid R. x superponticum, research published by the RHS allows us to clearly identify this taxon from others. This one R. ponticum hybrid is invasive and it’s in our gift to determine how it’s treated under the new legislation. If any other Rhododendron hybrids are invasive, and I’m not aware of any that are, they should be put through Risk Assessment and treated accordingly. As one Spanish colleague put it, raising concerns now is rather like “putting on a plaster before having an injury”.

Just as these species have leapt over the garden wall and escaped, we sometimes need to look over the garden wall ourselves and acknowledge the damage they’re causing in the wild. The last few sites for Starfruit, a beautiful water-plantain, are threatened with New Zealand Pigmyweed and the species might now be extinct in Britain. On Gower in south Wales the only British sites for Yellow Whitlowgrass are threatened by seven different species of Cotoneaster. And on the coast of south west Ireland, farmers are having to abandon fields that are being taken over by Giant-rhubarb.

Back on my Welsh hillside I’m surrounded by Rhododendron on all sides. In the valley below a magnificent Celtic Rainforest - home to countless rare mosses, liverworts and lichens – has been infested. Although the oaks still stand proud the ground beneath them and all the life it supported has been obliterated. Even where I’m standing, high in the hills, an advancing front of young Rhododendron saplings can be seen marching across the heathland. The Junipers won’t last for much longer. In a few years they’ll be skeletons under the Rhododendron forest.

Taking Action on Invasive Plants

Nicola Hutchinson
Head of Conservation, England and Wales





Just over a year ago I vented my frustration on this blog about the news that a long needed ban on the sale some of the most invasive non-native water plants had been announced and then immediately delayed for 14 months to allow for retailers 'to adjust'.  Fortunately we have finally reached the day when it really is against the law for floating pennywort, water primrose, New Zealand pigmyweed, parrot’s-feather and water fern to be sold in England and Wales.  Good, that's one thing out of the way.  But what else do we need to crack on with to really make a difference with this well documented environmental problem?

Over the past year the political arena for invasive non-native species has actually been quite a busy one, headlined by negotiations on an EU-wide regulation which is inching towards conclusion.  This regulation would set rules to help all Member States prevent and manage invasions, and it makes sense to do so at this scale.  Rarely does the natural environment respect political or administrative boundaries, but perhaps more importantly in this case are the trade rules that operate on an EU scale.  Hopefully one result of the regulation will be the total prevention of new potentially invasive species into the whole of the EU, and what is called 'regional cooperation' to tackle species causing particular problems in any one country.  So, first on the jobs list is one for the European Parliament to ensure it votes this regulation through.

The next step we should take is back on domestic shores, that's doing something with the review of the GB Strategy on Non-Native Invasives which has also taken place this past year.  Admittedly the strategy bit sounds a tad dull but if you cut to the chase then what this piece of national policy can give us is the opportunity to prioritise and work together on our biggest problem areas.  This might mean increasing our look out for new invasives in known trouble spots, or targeting resources to whole landscapes and catchments to truly rid them of established invasives.  There is a lot of activity already going on out there in our towns and countryside to get on top of species invasions, we simply could make a greater impact with some proper national support.  This one sits in Defra's camp for now, yet as ever we are ready to help where we can.

My final choice of where we need to go next with invasives is a challenge outside of government, one aimed at how we view the scale of the problem posed by non-native invasives.  We were recently asked by a journalist to comment on a story which headlined that gardeners who grow rhododendrons were to be criminalised by the new regulations coming through.  What we offered in response was a sense of perspective.  It is indeed true that a particular species of rhododendron (Rhododendron ponticum x Rhododendron maximum)  has escaped into the wild and causing major problems in areas such as Snowdonia and the wonderful Atlantic woodlands of Scotland's West Coast.  However, there are plenty of other varieties of rhododendron which grow merrily in parks and gardens without causing any damage; the same can be said for most invasive non-natives, where there is a bad guy there will be plenty of good alternatives.  We are always careful to point this out and what I'm seeking here is to urge everyone not to cause unnecessary concern through oversimplification or exaggeration.  Addressing invasive species is not a blame game, rather it is an action game: there is a problem and we have spent a lot of time working out precisely which species and issues we need to be concerned with. So let's focus our efforts, get on with the tasks at hand, and collectively make the difference we can.

Five invasive non-native aquatic plants banned from sale: our response.

Posted by Nicola Hutchinson, our Head of Conservation Programmes, England and Wales.

The problem of invasive non-native species (sometimes called alien species) is one of the best known environmental issues. Whether in towns or countryside many of us will have dealt with garden ponds or rivers choked with water weeds, watched Japanese knotweed grow and spread wherever it has taken root, and perhaps even admired the pink flowers of Himalayan balsam along a riverbank before thinking how much it has taken over.  Internationally, invasive species have long been recognised as one of the top threats to wildlife and the environment.  Ten years ago our own government set out a series of recommendations to deal with the problem and currently the European Union is considering a Directive as a way to better coordinate a response.  It's important stuff.

This is why it's great to hear the Government announce today that five of the most destructive invasive water plants will no longer be legally traded in England and Wales.  At last, some decisive and essential action.

Australian stonecrop, Crassula helmsii
one of the banned plants © GBNNSS

A range of specific measures are needed to really crack the problem,  with the most important of these being to curb the number of new incidences.  The primary mechanism for which is to simply ban the most troublesome from sale.  No matter how conscientious we as gardeners or landscapers may be, once invasive species are established in our gardens and parks they find their way over the fence into our streets and countryside.  Don't put them there in the first place and we've instantly removed a key pathway for invasion.

However, herein lies the twist with today's news.  The industry which trades in these problem species in England and Wales has been given a further 14 months to "adjust" to the new regulation.  This means that trading can continue until April 2014 - a move to allow existing stock and pre-orders of these invasive water weeds to be sold off.  Really, it beggars belief.  It's been agreed that these species are so damaging to our environment that it must become illegal for them to be sold, yet here we are inviting the biggest of all 'every last item must go' sale.  Are we really saying we want one last final push to get as many of these water weeds out of the shops and into the wild?

This sort of compromise agreement is one of the most frustrating aspects of environmental politics.  We are falling over evidence on the impacts of invasives; ten years ago the government recommended a ban on sale of the worst offenders, and 7 years ago the actual legislation was put in place to enable this to happen.  Yet, at the last minute, we've lost our nerve, ending up with a really smart move turning into a ridiculous one.

Government moved to halt the trade in ash trees, harbouring a non-native fungal invader, in response to the ash dieback crisis.  Questions were asked at the time whether this action was taken quick enough.  It seems we aren't learning our lessons well.

A sheep struggles through a channel choked with
Floating Pennywort © Trevor Renals

In these economic times, one appreciates the difficulties businesses may face when new regulations mean changes to the way they operate. However, in the case of invasive non-native plants, representatives of the horticultural and aquatic trades have been involved in discussions for well over a decade. Couple that with the legislation being put in place in 2006, the list of proposed species to ban consulted on in 2010, and this stacks up to ample time for traders and retailers to adjust already.  No-one in the industry can say they didn't know this was coming.


It makes me mad.  So I have to remind myself at these times that amidst the ditherings of others, here at Plantlife we've just been getting on with doing our best to implement solutions. Often that has meant direct action on the ground to clear established invaders from some of our most important places for wildflowers such as the Isle of Portland and the limestone cliffs of Torbay. And, with the principle of prevention being better than cure at the forefront of our efforts, we have researched which of the thousands of water and land plants available for sale pose the greatest threat to our native wildlife- this helps to hone our collective response, and gives the green light to the overwhelming majority of garden and pond plants available.   Indeed, to make it even easier for retailers and consumers we've worked with partners to publish reports and advice on which plants to choose as alternatives to those which cause problems (see our guides to landscaping and keeping ponds and aquaria without harmful invasive plants).

We've invested our time and resources into working out solutions to the invasive species problem because it really matters when it comes to conserving wild plants, incredible landscapes and other wildlife. Now we need everyone's help - do the right thing, it's easy, stop selling and stop buying these plants:

• New Zealand pigmyweed/Australian swamp-stonecrop Crassula helmsii
• Floating pennywort Hydrocotyle ranunculoides
• Parrot's-feather Myriophyllum aquaticum
• Water fern Azolla filiculoides
• Water primrose Ludwigia grandiflora, Ludwigia peploides, Ludwigia uruguayensis

And whilst you're at it, avoid these other ones too because they're equally as bad…

In the meantime, Plantlife applauds those retailers who've already made the shift to stop selling invasive plants, or who at least avoid the temptation to offer a 'buy one get one free' on curly waterweed!

For everything else you need to know about avoiding invasive plants and suggestions for fabulously non-invasive plants to grow have a look here.