Every year the debate is renewed when a controversial modern design wins a top award at the Chelsea or Hampton Court flower shows, and when plans are mooted for recreating historic gardens. Three years ago it was given extra impetus when Tom Stoppard addressed the issue in his successful play Arcadia, set in the early 19th century, some 50 years after most of the important gardens of English country houses had been turned into "natural" landscapes by the prolific Capability Brown.
Since Arcadia was written, two important garden restorations have afforded us the chance of appreciating what that 18th-century debate was really about. The Privy Garden at Hampton Court Palace has just celebrated the first anniversary of its restoration to the highly stylised design of the early 1700s - well before Brown came on the scene. As the shrubs grow we get a better idea of the intended formal effect.
Then in July, the National Trust opened the restored mid-18th century landscape garden at Prior Park, near the centre of Bath. In this compact space, on a steep slope offering marvellous views of the town, it is possible to see clearly how Brown adapted a fairly normal garden to accord with his naturalistic ideas.
It has only recently been established with confidence that Brown was one of the men behind Prior Park, although it certainly encapsulates his thinking. Most of the estate's early records were destroyed in a fire, but three of Brown's bills have now been discovered.
The estate was created in 1734 by Ralph Allen, who had made his fortune from owning a stone quarry outside Bath. He built his fashionable Palladian house - now a boarding school - at the top of a hill a mile south of the city centre, with the garden sloping north towards a valley.
The poet and satirist Alexander Pope was a frequent guest at Prior Park and helped design the garden. He was an enthusiast for the Rococo style then in vogue, with grottoes, cascades, statues and sham bridges. Few Rococo gardens survived the later fad for naturalism but they can still be seen at Chiswick in west London, Rousham in Oxfordshire, the newly restored Farnborough Hall garden in Warwickshire and on a huge scale at Stowe, near Buckingham.
Here at Prior Park, Pope's chief influence was on the wilderness garden close to the house. There was a cascade, a statue of Moses, a sham bridge, a river and a grotto, whose floor of cut pebble, sliced beef bones and ammonites has only just been uncovered. The grotto will be rebuilt in the next phase of restoration.
Pope died in 1744. Not long afterwards the garden was extended to reach the stream at the very bottom of the hill. In keeping with his style, another cascade was built on the central axis of the lawn, with water flowing down through two small ponds to a larger one at the bottom.
In 1755 the garden's most famous feature, the covered Palladian bridge, was built between the lower of the small ponds and the large one. Made of stone from Allen's quarry - now etched with graffiti dating from the 18th century onwards - it resembles a Greek temple, with Ionic columns on low balustrades supporting a shallow pitched roof. Such bridges were highly prized in important gardens of this period but only four have survived anywhere, including an almost identical one at Stowe.
Capability Brown was involved with Prior Park at the height of his popularity in the 1760s, before and just after Allen's death in 1764. Looking down from the mansion he saw a landscape that was, to his practised eye, too cluttered.
He liked the Palladian bridge but he thought that the fussy water features that ran down the centre of the lawn detracted from it. So he swept away the cascade, the stream and the upper pond, leaving the eye to be drawn by the bridge, spanning the pond just below a thickly wooded slope, with the large pond beyond it and the city away in the distance.
Between the house and the bridge is a plain expanse of lawn, where cattle sometimes graze, surrounded by trees - maple, wild cherry, hornbeam and yew - that are being replanted to their former density. It is a simple landscape, but one which typifies the romantic "picturesque" style that was advocated by Brown and reflected in art of the period, both in paintings and decorated pottery.
Brown does not seem to have made any effort to interfere with Pope's wilderness garden, probably because it is not in the direct line of view from the house down to other bridge and ponds. Over the years though, the wilderness has deteriorated. Not only the grotto but the architectural features have been destroyed or overgrown. When funds can be found this, too, will be restored, giving the chance to compare the garden fashions of the early and late 18th century.
The National Trust is rightly proud of the Prior Park restoration which was carried out in the face of severe practical difficulties. The first was the perennial problem of money. The work was able to begin thanks to four well-timed legacies and a pounds 250,000 grant from the National Heritage Memorial Fund, but the public appeal is still pounds 160,000 short of its pounds 400,000 target.
The other difficulty is access. There is no space on the site for a car park, except for half a dozen disabled drivers, and as it is near the city there is no convenient parking nearby. Local residents are apprehensive that visitors might park in front of their entrances or on grass verges, and the city was in two minds whether to allow the garden to be opened at all.
After a close vote they have given permission for a two year trial period. The Trust is urging visitors not to bring their cars but to come by train and use the frequent bus service from the station. Anyone producing travel tickets gets pounds 1 off the entrance fee.
At least there has been no controversy over the nature of the restoration. Prior Park escaped the 19th century reaction against Brown which saw the introduction of follies and temples into his landscapes. Since virtually nothing had been done to the garden for over 200 years, there was no question of having to obliterate later "improvements".
At Hampton Court Palace, by contrast, there was impassioned debate a few years ago before the decision was taken to restore the Privy Garden to how it looked in the early 1700s, when Henry VIII's Tudor garden was redesigned as a formal parterre to complement Sir Christopher Wren's south facade of the palace. The felling of ancient yews, to be replaced by young saplings, aroused particular emotion.
A year after it was unveiled, the garden is acquiring a more mature look, its young plants are now starting to spread, reducing the ugly expanses of bare earth. The "tunnel" of massed hornbeams on it west side looks impressive already, and will certainly improve with age.
Soon the arguments may start again though, because more development is planned at Hampton Court. It will be less radical than the work on the Privy Garden because there will be no attempt to take everything back to the 18th century: the fine Victorian plantings and the 20th-century mixed borders will be kept and improved. However, a part of the plan is to replant the avenues of yews and poplars in the park, which means cutting down what remains of the ancient trees. Stand by for more protests from the tree people.
There will be disappointment, too for Sir Roy Strong, the art and garden historian, who has long been pressing for the Great Fountain Garden, to the east of the palace, to be restored to its imposing early-18th-century design, as laid out in Leonard Knyff's contemporary bird's-eye view. This will not happen. Although it has maintained its original shape, the garden was redesigned in the 19th century and is today regarded as a fine example of Victorian formalism. This will remain.
Hampton Court is administered by the Government agency called Historic Royal Palaces. Another crown department, the Royal Parks, is also doing its bit for garden history. In Regents Park the Avenue Garden, near the south side, has been replanted as luxuriant Victorian borders, with fountains and free-standing yews and shrubs.
At another royal park in Greenwich there is a plan, maybe in time for the millennium celebrations, to restore part of the formal layout which was designed by the French master Le Notre, creator of Versailles. There will be some tree replacement here, too, as the great chestnut avenue is replanted.
The question whether the true earthly paradise is to be found in nature or in artifice will never be resolved. But by their own conscientious re-creation of historic landscapes the National Trust and the two royal agencies are providing us with the evidence we need to take sides in the debate, as well as offering feasts for the modern eye.
Prior Park Landscape Garden, Bath. Open daily, except Tuesday, noon- 5.30pm. No dogs. Admission pounds 3.80, children pounds 1.90, National Trust members free. No car parking. Bus every 10 minutes from station (every half hour on Sunday). Reduction of pounds 1 for visitors producing bus or train tickets (NT members get a pounds 1 gift voucher instead).
Hampton Court Palace, East Molesey, Surrey. Open daily 9.30am-6pm, except Monday opens 10.15am, and November-March closes 4.30pm. Admission pounds 8, children pounds 4.90. Privy Garden only, pounds 1.50.Reuse content