`This blessed plot, this England'. - Shakespeare. Three gardens - Great Dixter, Sissinghurst, and Hidcote - English landscape architecture at its best

IT'S encouraging to know that three of England's greatest gardens were created largely by amateurs. Great Dixter in E. Sussex, Sissinghurst in Kent, and Hidcote in Gloucestershire consist of a series of outdoor ``rooms.'' These are relatively small spaces enclosed by green hedges or rustic stone walls and filled with groupings of colorful flowers and shrubs - which will begin blooming soon.

The overall settings are spectacular. But because the gardens consist of manageable divisions, they offer practical suggestions for those with even the tiniest of flower beds. All provide sumptuous scenery for gardeners and nongardeners alike.

GREAT Dixter, eight miles north of Rye, is still being fashioned by Christopher Lloyd, one of its creators. Mr. Lloyd is a connoisseur collector of plants who loves to test new hybrids and play with color combinations. This gardener is also a premier writer, describing his garden's triumphs and failures in books, columns, and articles.

Great Dixter's design was laid out almost 80 years ago by Edwin Lutyens, a turn-of-the-century architect whose influence on garden structure is still felt today. At the time Sir Edwin began to practice, garden style dictated vast panoramas of field and woodland.

He proceeded to reduce this scope and reintroduced the concept of formal design, using the roomlike divisions that had been popular from Roman through Tudor times. In doing so, he made it possible for those with smaller plots of land to aspire to artistic achievement in the garden.

At Great Dixter, Lutyens laid out 18 distinct compartments. These were filled with topiary, a typical accompaniment to a ``room garden,'' and then planted by Lloyd's mother. It was she who filled one ``room'' with antique roses and who had young Christopher help her plant the meadow garden with a splash of bulbs and wildflowers.

While Lloyd has left some of his mother's plantings intact, other ``garden rooms'' at Great Dixter form a hot house of horticultural experimentation. This laboratory aspect can best be appreciated in the famous Long Border, a brilliant tapestry of plants measuring 70 yards in length and five in depth.

Best seen from the month of June on through the summer months, this magnificent garden planting is an ever-changing, riotous color mixture of perennials, annuals, bulbs, small shrubs, and even trees - something to be seen!

IN contrast to the evolving plantings at Great Dixter, those at Sissinghurst - less than an hour's drive to the northwest - are a static but living monument to Vita Sackville-West and Harold Nicolson.

The diaries and letters of this couple (particularly as depicted in the book ``Portrait of a Marriage'') have chronicled their nontraditional, but highly cultured and literate lives. However, their petty affairs can be boring and make one wonder what was so special about this man and woman.

A visit to Sissinghurst supplies the answer. It is a stunning work of art, created by two individuals who had no formal horticultural training.

They acquired Sissinghurst in 1930. It consisted of some ruined buildings and rubbish-strewn fields. ``I saw what might be made of it,'' Sackville-West wrote. ``It was Sleeping Beauty's garden ... a garden crying out for rescue.'' The two were to spend the next 30 years answering that cry.

Harold Nicolson designed the garden, and she planted it. He favored the formal approach advocated by Edwin Lutyens (a close friend of his mother-in-law), and created an austere geometric layout. He extended the concept of ``room gardens'' and used borders of clipped boxwood hedges to create ``rooms'' within ``rooms'' in many of the nine garden spaces.

Sackville-West then gave full play to her romantic impulses in planting her husband's design. She copied the old cottage garden style - lush, crowded arrangements of many different flowers - and added the idea of themes. Thus, she created the White Garden, described as ``the most beautiful garden at Sissinghurst, and indeed of all England.'' Every flower in this garden - fragrant roses, woolly lambs' ears, dusty millers, and many more - is either white or gray.

Each ``room'' has its own special motif. In early spring, for example, the Lime Walk is garishly filled with the reds, blues, yellows, and whites of daffodils, forget-me-nots, anemones, and bluebells. This part of the garden then rests while others - such as the herb and rose gardens - come into their own in the warmer months.

Sackville-West was protective of Sissinghurst. When it was first proposed in 1954 that she give the garden to the National Trust, she vehemently wrote in her diary, ``Never, never, never!'' But when she died in 1962, the family couldn't afford to pay the estate taxes, and the property came under Trust auspices.

THE enigmatic creator of Hidcote, Lawrence Johnston, on the other hand, was the first person to donate such a property to the National Trust. He did so in 1948, packed up his baggage and his dachshunds, and moved to southern France, leaving England and his magnificent garden forever.

Mr. Johnston is always referred to as ``the American,'' but he was so in parentage only. He was born and raised in Paris, and attended Cambridge University. Johnston became a British citizen in 1900 and acquired Hidcote in 1907, when he was 36.

There was nothing surrounding the hilltop Cotswold mansion, 35 miles northwest of Oxford, but simple farm land. Out of this, Johnston fashioned a masterpiece.

One of Hidcote's charms is that individual flower varieties are planted in small groups and then surrounded with grandiose atmospheres. Thus, the Pillar Garden is enclosed by immense sculptured pillars of yew, while one of its borders is a simple mixture of mock orange shrubs, purple lavender, and yucca plants.

As Sackville-West wrote in 1949, the 21 or so gardens at Hidcote appeal ``alike to the advanced gardener in search of rare or interesting plants, and on the aesthetic side to the mere lover of beauty.'' Where Johnston got his ideas from and why he implemented them as he did are mysteries.

He had money, which always helps. And as his passion for gardening grew, he became more knowledgeable - going on plant expeditions to South Africa in 1927 and China in 1931, and creating his own hybrids, such as Hidcote Lavender. Though he treasured, indeed insisted upon, his privacy, he entertained many of the beau monde. He is supposed to have designed Edith Wharton's Paris garden.

Under National Trust sponsorship, Hidcote's beauty is scrupulously maintained. In addition to its exotic topiary and theme borders, it features sweeping lawns, meandering streams, brick walks, a raised pool, and cozy gazebos. From spring through fall, there is always something of interest for even the most casual of visitors. It is somewhat ironic, however, to realize that this grandest of English ``room gardens'' was created by a man with an American inheritance and a French background.

EACH garden is an easy day-trip from London and best reached by car. A road atlas is most helpful in plotting a route. Signs are posted near each location, and pedestrians are quite willing to help with instructions. For the most current information on fees and opening times, buy a copy of the 1988 edition of ``Gardens of England and Wales'' (known as the ``Yellow Book'') for 1 upon arrival in England. This handy reference tool, available in most bookstores, provides detailed information on over 2,300 private gardens.

Great Dixter is in Northiam, about 8 miles northwest of the seacoast town of Rye.

The garden is a private one. There are parking and restrooms, but no refreshments. There are separate charges to see the gardens and the mid-15th-century farmhouse.

Sissinghurst is located in the heart of Kent, near a little town called Cranbrook. As a National Trust property, it offers a pleasant lunch and tearoom, a gift shop, restrooms, and a parking lot.

Hidcote is near Chipping Campden, about 35 miles northwest of Oxford and 12 miles south of Stratford-on-Avon. It features the same amenities as Sissinghurst.