Action à la cart: What does growing veg in a trailer have to do with saving the coastline?

Robyn Davies is the National Trust surf project co-ordinator for Cornwall, so she's a bit off her regular beat this morning. Instead of worrying about board wax and wetsuits, she's standing in the stable yard at Penrose, near Helston on the Lizard Peninsula, showing off a portable vegetable patch: a trailer full of leeks and lettuce. "Well, part of my job is raising awareness of the state of the beaches and the coastline. And growing your own veg cuts down on food miles, which helps to slow down the effects of climate change and protect our coasts. It's all connected."

Davies has already devised several visually vivid projects to highlight the coastal erosion we might expect in Britain with rising sea levels: at Godrevy, a famous surf spot on Cornwall's north coast, people were asked to guess, by planting bright-red flags, where the cliff might stand in 50 years' time. "Climate change isn't just about polar bears! It's about our coast too," Davies says. The resulting graphic image of coastal change shocked passers-by. But can we save the world via lettuce?

With the veg garden in a trailer, Davies aims for a gentle prod to hearts and minds through appearances at local events. "You might look at a lettuce and wonder what that is going to achieve. But every little bit does help. And you can grow such a lot in such a small space." The trailer garden is a perfect lesson in how to do it, with two rows of gorgeous frondy carrots, another of celery stems thickening up, a cherry-tomato plant covered in tiny green fruit, the green shoots of spring onions, a choice of different-coloured lettuce, and herbs such as camomile, dill, parsley and basil.

After chatting for a while, we take a tour with south-west Cornwall's visitor services manager, Layla Astley, who lets us into the old walled garden of the Penrose Estate. "We're hoping to have allotments here, and maybe even a community garden," she explains. The National Trust has committed itself to providing 1,000 new allotments across Britain, and hopefully some will be right here in this gorgeous, sheltered, baking south-facing spot. To register interest, visit www.landshare.net.

With both Landshare and its Food Glorious Food campaign, the National Trust is shaping up to be an active force in changing the way we eat. And Astley and Davies represent part of a new breed at the Trust, genuinely passionate about their cause. "It's not a bandwagon," says Davies. "This is something I totally believe in. Having supermarket-style choices in food is one thing, but there's nothing more satisfying than growing your own."

For summer events at National Trust UK properties, visit www.foodgloriousfood.org.uk

Home harvests: Learn to grow your own

Wimpole Hall, Cambridgeshire is holding a tomato festival, with a chance to taste many of its 50 varieties. 15-16 August, www.wimpole.org

Treasurer's House, York is holding a scariest vegetable monster competition. And there's something a bit different in the tea room: chocolate beetroot cake. 22-23 August, www.nationaltrust.org.uk

Standen, Sussex is celebrating National Kitchen Garden Day with demonstrations and tastings. 23 August, www.nationaltrust.org.uk/standen

Only got a windowbox? The Trust is after you too, getting people to grow ruby chard and beetroot on their sills. See the Food Glorious Food website for details