Why I want to see every rhododendron bush wiped off the planet
TO gardeners, the rhododendron is an eyecatching and attractive plant, with wine-red, delicate pink, deep purple or snow white blooms that are a colourful addition to any flowerbed.
But to conservationists and naturalists like me, it is an alien menace akin to a vampire sucking the lifeblood out of the countryside.
Once these sturdy evergreen plants have hopped over the garden fence, they run riot, taking over the land, shading the ground and becoming so dominant that flowers native to Ireland and the UK, or the animals that depend on them, can survive.
Like other non-native invaders, such as Japanese knotweed and Himalayan balsam, the rhododendron is completely out of control. And where it establishes itself, it is utterly ruthless in the way it obliterates everything in its path.
Now a study from the University of Aberdeen has found that even 30 years after rhododendrons have been cleared from woodland, the forest floor has still not recovered. It was not always this way. The wild
Rhododendron ponticum – from the ancient Greek for ‘rose-tree’ – was first brought to Britain from southern Europe in the late 18th century, to decorate gardens, parks and the grounds of stately homes.
To begin with, it behaved and stayed put. But in the Victorian era, breeders crossed the original plant with a closely related American species and created what Trevor Dines of UK botanical charity Plantlife calls ‘the Frankenstein plant – top of the list of the worst invasive species in Britain’.
This variety, dubbed ‘superponticum’, soon escaped from its parkland settings and began to rampage across the countryside.
Each flower can produce up to 7,000 seeds, which are dispersed by the wind over a wide area. A large bush may generate more than one million seeds a year.
BUT the plants spread in other ways, too – each one is capable of covering yards of ground with impenetrable branches. Where these touch the ground, they can root.
The leaves are poisonous, particularly so when young and tender, and become waxy, tough and unpalatable with age. So grazing animals such as deer, horses and domestic cattle won’t touch them and the plants grow unchecked.
There’s also evidence that they stop other plants growing near their roots, possibly by releasing noxious chemicals in the soil.
The result is that rhododendrons have spread far and wide. The latest report from Britain’s Forestry Commission estimates they cover roughly 3% of woodlands in England, Scotland and Wales.
That’s almost 1,000 square kilometres, more than two-and-a-half times the area of the Isle of Wight.
But what’s far worse is that they wipe out not just plants by creating a canopy so dark it deprives them of light, but birds and mammals, too, by destroying breeding habitats and food supply.
Even where trees survive, species such as woodland butterflies disappear because their caterpillars only feed on the flowers and grasses normally found on the forest floor.
The rhododendron has devastated populations of dormice, because these already endangered creatures depend for their survival on shrubs, bushes and trees that the invader has killed.
Even fish suffer, as streams which become shaded by rhododendron have no bankside vegetation to provide a habitat for the bugs and insects that form up to 80% of their food.
Rhododendrons also harbour a nasty disease, which is already causing major problems for the forestry industry because it can infect trees such as the larch.
And the plant is extremely difficult to get rid of. Take the cautionary tale from Dorset’s Brownsea Island, where the eccentric owner had allowed things to go wild for decades. When Britain’s National Trust took over the island in 1962, the landscape was overrun by rhododendrons which threatened one of England’s few colonies of red squirrels with extinction.
It took 50 years of back-breaking work to remove the plants, which were finally eradicated in 2012.
To mark the occasion, Dorset Wildlife Trust held a raffle – the prize was the chance to cut down the very last rhododendron!
Over the years, happily, the red squirrels have bounced back.
Elsewhere, though, especially along the milder and wetter western coasts of Wales and Scotland, known as the ‘Celtic Rainforest’, the rhododendron continues to run wild.
One problem is that you can’t use conventional methods to get rid of it, says naturalist and BBC One Show reporter Mike Dilger.
‘I spent a week cutting down rhododendrons in North Wales – it was a nightmare,’ he explains. ‘We planned to use chainsaws, but the foliage was so thick this would have been too dangerous, so we ended up having to saw off the branches by hand.’
Last February, Cheshire Wildlife Trust’s Congleton volunteer group spent two days fighting these invasive bushes. Volunteer Natasha Yamamoto describes the scene.
‘Armed with saws and loppers we hacked away at them,’ she says.
‘In the beginning, the sea of rhododendron seemed to go on for ever, but at the end of each day’s work it was hugely satisfying to see the hole we had opened up, and to think of all the wildlife we were helping.’
But cutting down the rhododendrons is just the start. Their stumps must then be sprayed with herbicides so they don’t regrow.
The seeds also remain in the soil – some believe the plant’s toxins do as well – so the entire top layer must be removed.
Even then, as the Aberdeen study shows, the problems are not over. In one Scottish woodland, the forest floor was still suffering three decades on.
Instead of the carpet of wild garlic, primroses, violets and ferns that should have been there, all the researchers found were mosses and liverworts, forming a thick mat which prevented other plants from growing.
So, having cleared woodland, conservationists must then keep sowing wildflower seeds.
Getting rid of rhododendrons is such hard work and so timeconsuming that it’s also incredibly expensive. Over 20 years, the cost of removing the plants from 1,000 acres of Cornwall rose to more than €4.5million, while the Snowdonia National Park Authority has estimated it would cost €11.3million to remove rhododendron from two square kilometres.
For the RSPB, rhododendrons are a major problem on 50 of their 200 or so nature reserves. They have called for a co-ordinated effort to eradicate the plant, with investment on a nationwide scale to protect our native woodlands.
Otherwise, it will return, zombielike, from the grave.
But they warn against demonising the plant: ‘It’s not really about hating rhododendrons – after all, it was people who brought them here, and allowed them to become established in the wild.
‘Rather, everyone has to be much more careful how we move animals and plants around the globe.’
AND not everyone loathes rhododendrons. Garden writer and broadcaster Stephen Lacey has mounted a spirited defence, praising them for their colour, beauty and sheer variety – more than 500 species in all.
He also suggests that part of our dislike of rhododendrons may be down to snobbery.
The writer and brilliant gardener Vita Sackville-West, a leading member of literature’s legendary Bloomsbury Group, dismissed them as being like ‘fat stockbrokers, whom we do not want to have to dinner’.
But I am afraid I will never be converted. The plant to my mind is pure poison. Nothing illustrates this better than the fact that honey made from bees that feed on rhododendrons can make people sick – so much so, that beekeepers have to think carefully about siting their hives in areas where rhododendrons thrive.
The writer Xenophon reported a case of honey poisoning among Greek soldiers in the 5th century BC, while 300 years later, soldiers commanded by the Roman general Pompey reportedly died from consuming rhododendron honey deliberately left behind by their fleeing enemies.
The toxic effects of the plant have also been mentioned in an episode of the BBC drama Sherlock.
This baneful plant is doing devastating damage to our flora and fauna as well as to our precious ancient woodlands.
The sooner we drive it completely out of our countryside, the better.
It’s an alien menace akin to a vampire sucking the lifeblood out of the countryside