A magnificent garden festival in (of all places!) Liverpool

If one were asked where in Britain might be the least likely location for a six-month-long International Garden Festival - a spectacular newly landscaped area of 125 acres, bordering a glorious expanse of river, a kind of nouveau paradise (in ambition at least) planted with a quarter of a million trees, blanketed with shrubs and flowers, cascaded and fountained, lawned and laked, hilled and valleyed - it is not altogether impossible that Liverpool would spring instantly to the lips.

But it is just possible that a six-month International Garden Festival on the banks of the misty Mersey River is precisely what Liverpool needs at this juncture. At any rate, from May 2 to Oct. 14, it is what this city - by dint of a gigantic act of land reclamation - has in fact got for itself.

Liverpool! Abandoned dockland, decaying buildings, depleted population, dereliction, a disturbingly high rate of teen-age crime and vandalism. Liverpool - described in a recent Times (London) profile as ''a phantom city with an essentially gentle people'' who have ''little taste for the disciplines and rigours which forge the impersonal skills which achieve material comfort.'' Liverpool - the success of its commercial past having somehow trickled away, leaving, like desert statuary, enormously impressive but oddly inappropriate Victorian civic buildings and monuments as the high-and-dry symbols of a vanished heyday. Liverpool - the notorious Toxteth District, scene of the worst riots among a number that flared in English cities in 1981. Liverpool in current financial crisis. . . .

Such matters are, of course, not generally of pressing interest to tourists understandably wanting to get away from it all, and happy, for the brief passage of a vacation, to go along with the rosy-half-view of nation or city promoted in travel brochures. Who wants to spend a relaxing period of recreation exploring slums or analyzing social disadvantage?

But the 1984 Liverpool International Garden Festival, the first event of its kind and magnitude ever held in Britain, is unavoidably and quite openly bound up with Liverpool's problems and hopes.

It is a novel achievement for those involved, this horticultural jubilee, though a certain amount of guidance has been gleaned from precedents in West Germany and other European countries, which have been holding garden festivals for a number of years now.

As Michael Smith, one of the team of landscape designers responsible for both the master plan of the site and for many of its individual gardens, points out: ''It was a brave choice of site. On the Continent the festival sites are often already planted with at least some trees. We had nothing!'' Nothing, that is, unless you count the vast garbage tip, and, along the River Mersey itself, the disused dock, railway sidings, the jetty, oil tanks, the abandoned, derelict beach. All this had to be cleared for a start - a total of 250 acres of it, described now as ''the biggest urban regeneration program ever witnessed in this country.'' In Britain today there is more derelict land, according to a recent survey, than there was 10 years ago, in spite of government's spending of (STR) 100 million ($145 million) on reclamation: It's a nationwide challenge.

So the Liverpool effort is both a symbolic achievement and a practical instance of urban revitalization. It has been done in about half the time usually taken by European counterparts. Reclamation by the Merseyside Development Corporation began in February 1982; building and planting in December the same year. The final result - and it will be a continually changing feast of color and planting through the six-month duration - promises to be an extraordinary display and celebration of horticultural skills and imagination, of fantasy and amusement, of family fun on the one hand and serious gardening interest and exhibition on the other. All told, it does not suggest a complete distaste among Liverpudlians for ''disciplines and rigours.''

But the Times article poured cold water on all of this. ''The supposition here,'' writes its author, Peter Lennon, ''is that if you plant exotic flowers in superabundance in the graveyard docks, horticulturalists lusting after blossoms will converge on the city from all over the world and be so irresistibly taken by the wan charm of disabled Merseyside that they will create a permanent tourist boom.

''The locals,'' he adds, ''are not impressed by such herbaceous remedies.''

Actually, nobody I spoke to seemed to expect the festival to be a simple panacea. Grant Luscombe of the Rural Preservation Association, responsible for one sizable section of the festival exploring aspects of ''Nature in the City,'' took a balanced view. He had come round to thinking the festival was, in fact, a good thing for the city. But it's just one item. ''Obviously one garden festival - though in the right direction - isn't going to solve Liverpool's problems.'' He, for one, is giving careful thought to the future of the site after mid-October. Certain parts, including the ''Nature in the City'' and main Water Features are already agreed to be permanent. ''These parts cannot have housing or factories on them,'' Mr. Luscombe points out. This is because the refuse dump still lies below, capped with a one-meter thickness of clay to make it horticulturally usable: But the refuse is rotting away down there, giving off methane gas. ''This is being drawn off, and incidentally is going to be used to heat the Festival Hall'' - another permanent feature.

The hall is the main building of the festival. Its precise future use for the city is not quite clear. ''A multipurpose sports and leisure center'' is the phrase offered at present, but during the festival it will house tropical gardens, all sorts of displays, and 15 major horticultural shows. It is an enormously striking steel-vaulted structure without internal supports, 122 meters long, 60 wide and 15 high. Each end is an opaque half-dome, but the larger part is clad in translucent polycarbonate panels.

Further permanent plans include an industrial complex and a housing estate. The nucleus of the latter has already been built in the form of show houses and gardens for the festival. One wishes it were possible to be more enthusiastic about the typical character and quality of Britain's current house-building practices - but the evidence of the '70s and early '80s offers little in terms of imaginative design, generous use of space, or even, in a number of cases, sound workmanship.

Whether the festival will permanently increase tourism to Liverpool also remains to be seen. Like many British conurbations with lingeringly unattractive reputations, Liverpool has much more interest and beauty, both in and around it, than people who have never been here allow. There is, for example, the Victorian architecture - superb in quality, outrageous in self-importance, amazing in fantasy. The early 18th-century Queen Anne style of architecture is appealingly represented by the old Bluecoat Hospital, a fine group of buildings round a lovely courtyard off Church Street. There are unusual museums and art galleries. A first-rate orchestra. And a newly opened exhibition-tribute to those famous sons of the city, the Beatles: ''Beatle City,'' it's called, a ''total experience,'' on Seel Street.

One possible danger is that people will come to the Garden Festival (there seems little enough reason to doubt that they will come in a great tidal wave) and be so absorbed by it that they won't actually see Liverpool itself. Day tickets are to cost (STR)3.50, and once you are in the festival grounds, there you must stay: If you want to leave and return on the same day, you will have to buy another (STR)3.50 ticket. (There are, however, going to be ''end of day'' tickets, allowing visitors to spend the last two hours before dusk closing time at the festival for (STR)1.) The message behind this ticketing policy is that the festival has not only enough interest for a day's visit, but also every possible facility the heart could require. ''A bit like a Butlin's holiday camp?'' I suggested mischievously to the ticketing administrator. ''No,'' he said definitely, ''much better class.''

Food will be available at numerous cafes and restaurants on the site. This means that a visit to the excellent basement restaurant in town where I had a delicious, imaginative lunch - La Grand Bouffe at 48a, Castle Street - will have to wait until dinnertime after dark.

This said, it certainly does seem true that the festival is large and varied enough, with the most astounding collection of gardens and plantings, to fascinate visitors. It will also offer ample peripheral enjoyment for those of nonhorticultural bent from 10 a.m. till dusk. Not the least of such pleasures will be chugging round the serpentine narrow-gauge railway that weaves its way through the whole site, drawn by small-scale steam or diesel locomotives.

But to those of horticultural bent, the festival is certain to be a field day , and even perhaps the experience of a lifetime.

The British have never seen anything like it. International participants, each providing a garden somehow expressing national character, include Japan and China, Belgium and Holland, Italy, Greece, West Germany, the United States, Egypt, Israel, Denmark, Turkey, Thailand, India. It is to be a veritable horticultural United Nations.

No less interesting will be the strong British contributions - gardens ranging from pure whimsy (things like a ''Jam Garden'' and a ''Beatles Maze'' complete with ''Yellow Submarine'' and ''Octopus's Garden'') to serious-minded, subtle plantings by such top-ranking organizations as the Royal Botanic Gardens at Kew and the Royal Horticultural Society at Wisley.

Whether the detractors approve or not, it is likely that a large number of Britons are sure to be drawn to Liverpool by this festival because not only do they love gardening (spending an estimated (STR)750 million a year on it), but also they must be the world's most avid garden visitors. Garden visiting is an almost obsessive national outdoor pastime. The English Tourist Board recently announced an estimate of more than 20 million garden visits made in England alone last year. These can range from the Sunday afternoon annual opening of small private gardens for charity to stately home gardens open all summer to the amazing array of great gardens that have become virtual meccas - such places as Sissinghurst, or Hidcote, or Stourhead.