Step off the open cliffs into the shelter of the trees, and the coast changes utterly. Here on the wooded northern shore of the Helford river lie two of Cornwall's great subtropical gardens, Trebah and neighbouring Glendurgan, deep green ravines tumbling down through giant leaves to their own private beaches on the water.
Palms and tree ferns, rhododendrons the size of houses, leaves of gunnera broad enough to shelter under: this is a jungle in Cornwall, grown in the mild air of a drowned river valley.
Both gardens were created in the nineteenth century by members of the Fox family, prosperous Quaker shipping agents from Falmouth.
Their business gave them contacts across the whole trading world, the captains and merchants of a great port at their disposal, and they used them to bring home seeds and cuttings of exotic plants from distant continents, setting them to grow in the soft, frost-free climate of these sheltered valleys where the sea holds off the frost. The result is extraordinary.
The gardens fill steep ravines cut into the slate that fringes the Helford, which is not an ordinary river but a ria, a valley drowned by the rising sea, its wooded creeks winding inland like a Cornish fjord. Glendurgan, with its famous cherry-laurel maze planted in 1833, is now in the care of the National Trust; Trebah, next door, is run by its own charitable trust.
Both open their gates to the coast path walker who wanders in from the cliffs, and between them they hold plants gathered from South America, the Himalayas, Australia and the far Pacific, all thriving here on one sheltered Cornish hillside.
As you explore, look for several things in turn. First, the giant gunnera, its rhubarb-like leaves rising well above head height on the damp valley floor, prehistoric in scale. Second, the tree ferns and palms that give the ravines their jungle character, and, in spring, the great banks of rhododendrons and magnolias in spectacular bloom.
Third, look down the length of each ravine to the glint of the Helford at its foot, and the private beach where the garden meets the tide. Fourth, at Glendurgan, find the celebrated maze of cherry laurel, best seen from above as a green coil laid into the hillside.
And fifth, watch and listen for wildlife: woodland birds fill the sheltered valleys, herons and waders work the Helford's muddy creeks, and the exotic blooms hum with insects. Take care on the steep garden paths and the wooded coast path, which can be slippery underfoot.
The story to carry with you belongs to Trebah's beach. For a century it was simply the tranquil foot of a beautiful garden, where a stream ran out across the sand into the Helford. Then, in 1944, it was pressed into the service of history.
In the build-up to the D-Day landings, this quiet Cornish cove became an embarkation point, and American troops of the United States Army filed down through the garden and out across Trebah beach to board their landing craft, bound for the beaches of Normandy.
It is a startling thought to hold as you stand among the tree ferns: that this most peaceful of places once sent men off to one of the greatest undertakings of the war.
From the gardens the South West Coast Path continues along the wooded shore towards Falmouth, in and out of the Helford's lovely creeks. On this stretch, look out for the seasonal Helford ferry, a small boat that carries walkers across the river mouth and saves a long detour inland; check its running times, for it is a highlight of the day. Then walk on beneath the trees, with the drowned river gleaming below and the jungle valleys behind you. Walk safe.
