It's that horrible holiday moment, idling on the Tarmac of a stationary motorway with all the plastic surfaces of your car heating up to egg-frying temperature. The only redeeming quality of a five-hour drive with a car full of luggage is that just occasionally you find somewhere amazing to stop, and then, for a moment, all life seems to make sense.
The A303 is the holiday route for anyone heading to Devon and Cornwall, and is rich in good gardens. Stourhead, East Lambrook and Tintinhull are world-class gardens, respectively three, two, and half a mile from the tractor-studded A-road. Each offers a different kind of peaceful respite to the teeth-grinding driver: Stourhead is a perfect English landscape garden around a circular lake walk with views that could make any photographer look expert. East Lambrook was immortalised by writer Margery Fish in We Made a Garden. One of Britain's prettiest cottage gardens, it is currently being restored with the help of teams of volunteers, and is open daily except Monday. And Tintinhull is a 20th-century formal garden for an 18th-century manor, much admired by the horticultural cognoscenti. The National Trust opens it Wednesday to Sunday, 11am to 5pm.
But this year I detoured a bit further than usual, to North Devon and Rosemoor, the RHS's western outpost, about 20 minutes' drive from Okehampton. Living up to its name, there are roses in perfumed quantity at Rosemoor the day I visit. In fact, so many are tumbling everywhere in so many different colours that it looks like the front of a cheesy 1970s box of chocolates. In
every direction, herbaceous borders lead away, all with the immaculate labelling which is the great advantage of an RHS garden – you can actually find out what that plant you like is called – and, often, buy it in the plant centre afterwards.
This time, though, my purpose was to visit the newly finished Square Garden. A hot little suntrap, it has been expertly planted with drifts of bright reds and yellows, including the bronze-leaved dahlia "Bishop of Oxford", bearing gaudy orange blooms. Foliage plants are interspersed, with Euphorbia wallichii providing a 4ft-high blast of zingy lime-green at the back of the bed, and Sambucus niger bearing dark, wine-coloured leaves with much fancy fringing.
Touches of crazy, velvety mauve complete the picture, such as Lobelia "Hadspen Purple" and a Penstemon called "Vesuvius" that is particularly eye-catching. And after an hour at Rosemoor, I get back on the road, my blood pressure considerably lower. One more recommendation for taking a horticultural detour.
RHS Garden Rosemoor in Great Torrington is open daily from 10am-6pm. For more information, visit www.rhs.org.uk
Green getaways: Refreshing stop-offs
Going up north or heading down south? Ten miles from junction 17 of the M6, just north of Stoke-on-Trent, this Victorian fantasy extravaganza boasts Chinese pavilions, an Egyptian pyramid and huge evergreens to picnic beneath. Totally nuts but gorgeous. www.nationaltrust.org.uk
Yorkshire Sculpture Park
Two miles from the M1, junction 38, just north of Barnsley, lies an amazing landscape with works by Hepworth and Moore. One for kids who need a run around. www.ysp.co.uk
Heading for Holyhead? Ten miles from the A5 at Betws-y- Coed, elegant terraces give way to huge Snowdonian views, with a Himalayan feel to much of the planting.