Why Benmore Botanic Garden is felling hundreds of trees

But the calm of the garden – much to the sorrow of those charged with nurturing it and the visitors who love its vibrant colours – is being disrupted, as work begins to tear down hundreds of its trees.

The work to clear more than 350 larch trees, some more than a century old and towering more than 130ft high, has been deemed necessary to tackle a quiet killer.

Carried on the breeze, the fungus-like pathogen Phytophthora ramorum has made its way from the southwest coast of England to Scotland’s southwest coast and the Argyll botanic garden near Dunoon where it is placing at risk the species most susceptible to its rapid ‘black death’, hundreds of larch trees, and a host of other plants.

Now, to halt the killer pathogen’s progress and protect other species from falling victim, the world renowned Royal Botanic Garden Edinburgh which operates the Benmore site is to systematically remove every single one.

The loss will leave some parts of the garden brutally exposed: one spot where 60 larch have grown for decades will be levelled, leaving a gaping hole in the landscape.

Elsewhere, tree experts will have to scramble over steep rocks and navigate narrow ledges to reach individual trees growing in the most awkward of places.

The trees will then have to be carefully dismantled bit by bit.

The task and financial costs of the huge job on a garden site spanning 49 hectares (120 acres) is challenging enough, but there are also concerns over how the loss of so many trees might affect the garden’s other plants and even its wildlife.

In some areas, towering larch trees had been deliberately planted in the 1920s to create wind breaks to protect other species for decades, while some shrubs which favour the shade have thrived beneath its canopy.

It remains to be seen, say staff, how newly exposed plants may cope, while others may suffer as routes are created to enable workers and machinery reach trees and remove fallen timber.

There is a host of other impacts: for wildlife, larch cones provide a source of food for seed-eating birds and red squirrels, and its deeply rutted bark is shelter for insects.

And for visitors, there will be a significant impact on the garden’s dazzling autumn colours: deciduous larch is one of the season’s stars, with its needles turning a glorious golden before being shed.

So, it’s perhaps not surprising that Peter Baxter, the garden’s curator, fears the loss of its larch trees is one of the most significant events in its history, on a par with Hurricane Low Q, which, in January 1968, ripped across Scotland.

At Benmore, the storm destroyed more than 500 trees, many of them 40m tall and which took more than four years to clear.

“I see this as most probably being the most significant landscape challenge within Benmore since the 1968 hurricane, and that had a devastating effect,” he says.

“It can be argued that after that event, there was a question mark over whether the garden would ever reopen properly again.

“But it also opened up certain parts of the garden that enabled future planting opportunities.”

He is trying, he adds, to put a “positive spin on it” but concedes the disappearance of Benmore’s 350 plus larch trees over the next three years will be significant.

“In certain areas, visitors will notice a total change, and it will feel totally different, the microclimate will change,” he adds.

“In other areas, if they’re familiar with the garden, they might remember a certain big tree that’s not there anymore.”

Last summer, Forestry and Land Scotland (FLS) said all larch trees in forests in south-west Scotland would be sacrificed by 2032 in a bid to stop the disease, first encountered in Cornwall in 2002.

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The move aims to create breaks in the pathogen’s path and will eventually see an estimated 10 million trees lost.

Because the pathogen favours damp, rainy conditions, the risk is greatest in western Scotland.

In Arran alone, work is underway to clear almost half a million larch trees. But further inland, at Gleniffer Braes, on the outskirts of Paisley, a confirmed outbreak has led to 3,500 trees marked for destruction.

Some of Scotland’s best loved beauty spots are also affected; earlier this year Forestry and Land Scotland (FLS) began felling larch trees at locations across the Trossachs, including Braeval, Balmaha and at Loch Ard.

The loss of so many larch is compounded by the impact of ash dieback, a fungus which will lead to 95% of UK ash trees being lost.

Of key concern at Benmore is halting the threat from Phytophthora ramorum to other species: while the pathogen favours larch, it can also affect rhododendron, viburnum, camellia and Pieris, among others.

Benmore has around 3,000 rhododendrons spanning around 300 species, many transferred to the west coast garden after being grown in the RBGE Edinburgh nursery in the 1920s and 1930s and is described as a “living textbook” of the genus.

“Most of the work is preventative,” stresses Dr Matt Elliot, RBGE Plant Health and Biosecurity Scientist. “Currently only a few have been infected, so it’s a case of us getting ahead of the game.

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“It’s a fungal like pathogen which is blown around in the air, the spores land on needles and infect the tree.

“Once infected, death happens quickly; a group of larch can go form relatively healthy to dead in 12 months or so,” he adds.

“The timber gets brittle, they tree can blow over, some bits can fall off.

“Dumfries and Galloway is by far worst hit,” he continues. “If you drive the back roads to Newton Stewart you can see the worst areas of trees have had to be removed.”

Felling certain trees will bring an array of difficulties, adds Pete, with some trees taking three people a week to remove.

“If this was a normal forestry harvesting site you can do a clean sweep but we can’t because part of the plant collection that grows underneath the larch,” he adds.  “They have to be systematically taken apart.”

Then comes the problem of what happens to the timber: ideas range from timber for boat building to garden furniture.

Dr Elliot, meanwhile, points to how other locations have coped with the enforced loss of so many larch trees could bring opportunities.

“Some have taken the opportunity to have a rethink and looked at moving away from the Victorian garden model and do something different.

“We are a research organisation, conservation is our main aim,” he adds.

“It might give us an opportunity to try other species that need conserving and that are resistant to this.”