The gardens at the Château de Vauville near Beaumont-Hague work with their conditions

As the seaside holidays begin I find myself wondering what it is like to garden by the sea. In Britain it depends on whether you have the blessing of the warm Gulf Stream. What happens over the English Channel? Does the Gulf Stream ever become French?

On the coast of Normandy I have just found out.

On the Cotentin peninsula, a few hundred yards from the sea, the gardens at the Château de Vauville near Beaumont-Hague are a masterpiece of thoughtful ingenuity. The west wind is strong and the salt blows persistently from the nearby Channel. Undaunted, two generations of the Pellerin family have turned more than 10 acres of acid soil into a garden now recognised as an official monument historique.

I disembarked at Cherbourg from a Brittany Ferries crossing, motivated to see it by the excellent new section on garden tours on the company’s website. It is recognising the fascinating diversity of Normandy gardens within motoring distance of its terminal. I wrote recently of the fine formal garden at Brécy, which also features in its recommended tours. Others can be accessed through the specialist British site www.frenchgardenstoday.co.uk, which does so much to show British holiday motorists that their passion for gardens need not be left dormant when they wave goodbye to Dover.

The Château de Vauville began life as a centre for duck hunting. The present owner, Guillaume Pellerin, explained to me that he and his parents had changed from hunting ducks to hunting plants. In the most unusual setting they have made a garden that enlarges our ideas of the possible. It has a warm climate but a very windy exposure. The Pellerins have patiently developed shelter belts, exploited the rarer corners of the family of bamboos and survived storms as fierce as the 1987 gale that knocked down 250 of their trees. They accept that the winds will flatten off the height of their plantings in open aspects and keep the whole place at a level height of about 10 feet. They have now collected more than 1,300 species, many of them evergreen. To walk through their level canopy is to walk through a sort of botanical bush-cum-jungle, with the curious sense that if one was twice as tall one could see out on to open sea. The range of rarities is disorienting, few of them known in British gardens. Did you realise that Machilus sinensis is laurel-like in leaf and that it will go well with the cutting edges of the leaves on Eryngium pandanifolium?

The idea for a global garden here came from the elder Pellerins’ postwar trip to Sri Lanka. It has been sustained by their son, Guillaume, and his indefatigable wife, Cléophée, who continue to receive rare plants from as far afield as China. They preside over the greatest botanical collection in any Normandy garden.

It takes imagination to realise that plants such as Beschorneria yuccoides, with its reddish spikes of flower, can be grown in big drifts, what lovers of ornamental grasses like to call the prairie style. In the 1980s and 1990s the Pellerins ran the garden shop in Paris whose name best summarised the particular French genius for virtual gardening. Called Jardin Imaginaire, it appealed to clients on the Rue Jacob who would much rather not encounter a worm in real life.

As the Vauville garden grew, the Pellerins closed the shop for their jardin maritime, where fantasy is no less important. They are now helped by two gardeners and teams of students who wear the garden T-shirt and breathe eagerness. The site is open every afternoon in August and September from 2pm-6pm, with a chic garden boutique that keeps the traditions of Jardin Imaginaire alive. It makes a calm staging post on your journey if the circling paths and big clumps of gunnera begin to wear you out.

I was fascinated to see how flattened trees will sometimes regenerate at odd angles and how favourite plants of British connoisseurs are so much bigger and better in this extraordinary micro-climate. Eucalyptuses sometimes adopt a horizontal line of growth after the main trunk has become too high and been broken. Trachycarpus will not exactly grow in most of inland Britain but at Vauville specimins have adapted to the wind by rooting outwards on their sheltered side only. The gardens are full of such tributes to plants’ flexibility and it is worth watching for them among the array of Mediterranean and semi-tropical rarities. Of course the big spiky echiums are enviable, loving the frost-free climate. As ever, ginkgo trees are able to surmount unusual conditions. Vauville has rare varieties but it is awesome to remember that the basic Ginkgo biloba, a tree on earth before the ice age, is just as happy as a street tree in the vile climate of New York as it is here in a weird blend of wind and warmth.

The first experiments in the garden began near the house, where the old moat gave even greater shelter. Even now, cinnamon trees, camphor, fine dicksonia tree ferns and rare eucalyptus grow freely from year to year. Why bother with all those “temperate” greenhouses in British botanical gardens, heated on ever-expensive fuel, when most of the same plants can be seen within half an hour of unloading the car off the ferry at Cherbourg?

I have seldom learned so much that was new to me in an outdoor garden only a day trip from London. Can we all try Ilex rotunda from Shanghai one day? At Vauville it has the most impressive big-toothed green leaves. What are the names of all those figs with glossy green leaves, not the rough ones that appear in Britain more readily than the delicious fruit? What does Monglietia from the Himalayas look like when it flowers? Is your climbing Hydrangea seemannii half as big or well-flowering as the Pellerins’ specimen against an inner garden wall?

Most of us would have dismissed the idea of a world-class garden in such a sea-site as a fantasy. It works because it works with the conditions. It does not try to defy them. There is this basic lesson here for all of us, even if we lack the energy of the two generations, male and female, that have improved this family garden over the past 60 years. If we start with similar lists of plants that we “simply must have”, we end up with gardens that look predictably alike. Unusual conditions ought to make us think unusually. In gardens, too, adversity can be an ally.