The sublime luxuriance of camellias: Anna Pavord is reduced to snail's pace by the beauty of Cornwall's Mount Edgcumbe Gardens

IT IS only a five-minute voyage on the ferry from Plymouth over the Tamar, but it feels like going abroad. It is actually a floating bridge, rattling ponderously along fixed chains, but sunlight transforms it into something much less workaday, and the harbour, when I crossed to Cornwall this week, was shimmering as seductively as a Turner. At this time of the year, Cornwall is at its most beguiling.

I went down to look at the national collection of camellias at Mount Edgcumbe Country Park, which has nearly 500 different kinds. Anyone in the know would have left the car in Plymouth and gone over on the foot ferry, which lands you at the country park's formal gardens. I took the car ferry, no hardship but more roundabout.

The house at Mount Edgcumbe is perched high on the north end of the peninsula, facing Plymouth Sound, but the park and gardens stretch round the coast to Rame Head and the open sea. The situation is dramatic in the extreme and ever since the place was first laid out by the Mount Edgcumbe family in 1547, it has been popular with tourists: 300,000 a year now visit the park - free.

The opinionated garden writer and reformer John Claudius Loudon went in 1842, and found 'the effect on the mind sublime in the highest degree'. Earlier, the novelist Fanny Burney had been taken around, and commented on the constantly changing nature of the landscape, 'a desert island one moment and a luxuriant country the next'.

Sublimity and luxuriance slow you down, and it was a long time before I got to the camellias. For 22 years, Mount Edgcumbe has been jointly owned by Plymouth and Cornwall councils, which are carrying out restoration of this Grade I historic park and garden. Formal flower beds, recreated in Victorian style, have been planted up on the east lawn. A superb shell seat has been restored by the jeweller and grotto artist Diana Reynell. This last alone would be reason enough to visit the garden.

Much further away, at the point where the foot ferry comes in, and connected to the house by a long formal avenue of chestnut, oak and sycamore, is an intricately linked series of formal gardens - Italian, French, English - each with its own garden building. The orangery that fills the sea end of the Italian garden is now a cafe. At the other end is an Italianate staircase topped with statues of gods.

The Italian garden and the French parterre garden nearby were laid out by Richard, second Earl of Edgcumbe, and his wife, Sophia, some time after 1800. Had it not been for the invasion scare of 1779, when it looked as if the French and the Spanish Second Armada were going to attack Plymouth, these gardens might never have been created. The War Office feared that an attack on the dockyard might be made from the cover of Mount Edgcumbe's woods, which then dropped uninterrupted from the house down to the sea shore. It ordered all the trees to be felled.

The gardens could not have happened, either, without the Great Hedge, an astonishing stretch of ilex that protects this patch of ground from the salt and fury of sea winds. It is about 40ft high and old photographs show gardeners spread-eagled against it like small spiders, clipping at it with hand shears. Now it is cut from the comparative comfort of a hydraulic lift.

Many of Cornwall's most important gardens - Tresco, Trewithen, Caerhays - owe their status to their collections of rare exotics. They are, for the most part, woodland gardens made within the past 100 years by families such as the Williamses and the Foxes. Mount Edgcumbe, though it has some good plants (including a stunning Pinus patula from Mexico and some huge cork oaks), is important because of its wider place in the history of gardens.

It forms a surprisingly intact and rare example - rare not just in Cornwall but in England as a whole - of a landscaped garden of the early 18th century, with fine garden buildings, and superbly manipulated views. Later additions enhanced rather than detracted from the original conception. It is miraculous that the entire park, which covers more than 800 acres, should still be intact - and that the two councils involved are committed to restoring the gardens to such a high standard.

Now for the camellias. The bulk of the collection is planted around the upper part of a natural amphitheatre in a valley to the south-east of the house. You can get there by crossing the park in front of the house. This brings you to the old driveway that curves round the right side of the amphitheatre. If you take a wide track to the right it brings you to the deer fence at the top edge of the woodland, with views over a fine group of stone pines to an ecclesiastical-looking folly and the sea beyond.

The collection was started in 1976 with a gift of 70 plants from the International Camellia Society. Then 100 mature plants were brought from David Trehane's garden in Truro, and a selection of Cornish varieties came from Gillian Carlyon's old garden at Tregehan. The locals are blase about camellias, which have been blooming outside in Cornwall since late December. But to an upcountry visitor they are a breathtaking sight. When you see so many flowering together it becomes very much easier to sort out good garden varieties.

'Brigadoon', a C. x williamsii hybrid raised in the US, was looking good covered in rose- pink flowers. You missed the gloss on the leaf though, when compared with C. japonica varieties such as 'Emmett Barnes'. 'Brigadoon' survives bad weather quite well and this is an important consideration when growing camellias outside the balmy West Country.

If you strike out past the folly and pick up the coastal footpath, you will, beyond the triumphal arch, come to the best camellias of all. These grow just as Englebert Kaempfer, the German who first wrote about camellias for European gardeners, must have seen them in Japan in the 17th century. A footpath leads from the coast path up into 'the zig- zags', planted at the end of the 18th century with arbutus, myrtle, mimosa, laurustinus - and camellias.

The trees, with red, pink and striped blooms, at first tower way over your head. As you climb, steeply, with the sound of the sea pounding on the rocks below, you begin to be able to look down on top of the trees. This is Mount Edgcumbe's best- kept secret.

Mount Edgcumbe Country Park at Cremyll, Torpoint, Cornwall, is open daily. The house and Earl's Garden are open 1 April to 31 October (11am-5.30pm), admission pounds 3. 'The English Garden Tour' by Mavis Batey and David Lambert (John Murray, pounds 25), has a full account of early visitors. The directory with details of 550 national collections is available from the NCCPG, The Pines, Wisley Garden, Woking, Surrey GU23 6QB, pounds 2.50 including p&p. 'Gardening with Camellias' by Jim Rolfe (Godwit, pounds 25) is the most recent book on the subject, though written for a New Zealand audience.

(Photograph omitted)