If you’d gone down to the woods the other day, you would have been in for a big surprise. No, not teddy bears, but a dozen men and women, aged between 17 and 75, bashing the rhododendron bushes with anything that came to hand. It was no picnic, I can tell you, grunting and sweating among the smoke and the midges in that tangled jungle. Although on paper it was, in fact, a holiday.

This particular woodland was on the Isle of Arran, and the roddy-bashers were of all shapes and sizes: a lawyer, postman, GP, journalist, call-centre executive, charity worker, a handful of students and a couple of retirees, all of whom had signed up for a week’s Thistle Camp with the National Trust for Scotland (NTS). Their mission was to join forces with the rangers on the NTS’s Brodick estate to lead an assault on the enemy — the rhododendron.

The flowering bushes are one of Arran’s big attractions, and in the woodlands and gardens around Brodick Castle they put on a wonderful display, especially in the early summer. But they also spread prolifically, invading neighbouring lands and smothering all native growth. So in order to allow the deciduous trees to regenerate and to continue to provide a home for Arran’s cherished population of red squirrels, the ruddy roddies needed taking down a peg or two.

So there we were, slashing, chopping and burning in that midgy gloaming, on a sort of boot camp for country lovers with a conscience. Our frenetic activity attracted the attention of a passing family ambling along one of the estate’s woodland walks. They posed for photographs with us, pretending to join in with the roddy-bashing for the sake of the camera. “Who did they think we were?” asked somebody when they’d gone. “I’m a Celebrity . . . Get Me out of Here?” The National Trust for Scotland Conservation Volunteers runs a programme of Thistle Camps from March to October. These conservation holidays usually take place in wonderful locations, from Fair Isle in Shetland to Grey Mare’s Tail in the Borders.

Tasks vary from searching for bats to building drystone walls, from roddy-bashing to helping a small island community make hay. Accommodation can be a bothy with basic facilities or a comfortable lodge (as at Brodick) where all linen is provided.

Among our group were several veteran thistlers, and a couple of novices. At dinner, the veterans reminisced about the loos in Glenfinnan, the showers in Inverewe, and how to keep beer cool in Glen Affric by immersing it in the river. Younger members swapped notes about their favourite chocolate biscuits and the Tunnock’s Teacake Appreciation Society.

The Arran camp is one of the most popular of the Thistle Camps and quickly gets booked up, perhaps because it involves a romantic journey across the water.

Location apart, motivations for being there were many and varied. Robin, a lawyer and a first-timer, had stumbled on Thistle Camp volunteers when out hill walking. “I was impressed. They were mending footpaths, miles from anywhere,” he said. “As a walker, I thought I should do my bit, too.”

For Matt, a call-centre executive in his early twenties, part of the interest lay in the cross-section of people. “I like the opportunity of sharing ideas with other age groups, the sort of people I don’t often meet,” he explained. “My friends say I’m mad, but I really enjoy it, and I can see no appeal in going to Spain to get sunburnt and drunk.”

And then there’s the sheer inexpensiveness. For a week in the great outdoors among some of Scotland’s loveliest scenery, you pay between £50 and £100, and that includes all accommodation and food, and sometimes even the cost of travel, as well. All you have to provide is the hard labour — and even that is not too taxing. “Don’t overdo it,” counselled our group leader, David Dreghorn, on the evening we arrived. “You’re here for a break. And to work.”

The work wasn’t all about getting up close and personal with the roddies. For a couple of days’ light relief we were armed with mattocks and pinch bars and redeployed into another part of the NTS property on Arran — the 6,500 acres around the island’s highest mountain, Goat Fell.

The task was to repair and improve the footpath that snakes its way up the classically glaciated Glen Rosa. Fortunately, the weather was glorious, the air so clear that the top of Goat Fell looked tantalisingly close.

Work doesn’t feel like work in such surroundings. From the ranger in charge, we learnt about cross-drains, pitching, gullies and path trays; you don’t realise how much architecture and hard labour there is to a footpath until you actually work on one.

As the week wore on, progress on the path and rhododendrons seemed laborious and slow, but Kate Sampson, Brodick’s senior ranger, declared herself very satisfied. “We’ve worked out the contribution that volunteers make towards easing our workload,” she told me. “And it is the equivalent of having a further 2.2 full-time staff.”

For this year, I reckon about 0.01 of that 2.2 was me.

Details: National Trust for Scotland, 0131 243 9360, www.thistlecamps.org.uk

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