Last week's cover photograph, incorrectly credited to Sharon Farmer, was actually taken by Betty C. Ford.

Summertime? Its heat drives city-dwellers to the nearest park or public garden. Why not discover Washington's most beautiful secret gardens before the summer heat overcomes you?

Down through history the garden has been beloved. Pliny the Younger, like many of the leisured Romans, designed numerous gardens at his rural retreat, including one overlooked by his private apartment, where he excaped the bustle of his large Roman household. Charlemagne is said to have interested himself in gardens, and one decreed a list of 60 plants and flowers to be planted in the imperial gardens. Petrarch designed two gardens for himself, one in which to contemplate, and one for study. Thomas Jefferson kept a garden notebook for almost 60 years. But the Moguls, who ruled India from the 16th to the early 18th century, were among those most dedicated to gardens. The Emperor Shah Jehan, famous for his Taj Mahal, built the Red Port in Delhi afterward. Within the fort, Shah Jehan's, famous for his Taj Mahal, built the Red Port in Delhi afterward. Within the fort, Shah Jehan's plaque still hangs on the garden wall of his palace:

If there is a paradise on earth,

it is here,

it is here,

it is here.

For most people living in Washington, however, the time of large private gardens is long gone, and the city's public parks are the only resort. These gardens, however, are usually filled with noisy picnickers, volleyball players and dog-lovers coursing their afghans.

So we have compiled a list of the beautiful, not-too-frequented gardens still to be found in Washington. Only a few of these are public parks open to the public, for these parks, like Dumbarton Oaks, are well-known and crowded. Most of the gardens chosen are part of a cultural institution, such as the National Portrait Gallery/National Museum of American Art or the situtions can be happily combined with enjoyment of the gardens. Only one of the gardens on the list, in the grand tradition of the medival cathedral or monastery, is the garden of a church.

Perhaps among these gardens you will find, if not a paradis like Shah Jehan's, at least a green retreat from the heat of summer. What could be more refreshing than a tour of glades, gardens and oases? BISHOP'S GARDEN, Washington Cathedral, Wisconsin and Massachusetts Avenues NW. Open daily, 9 to dusk.

On the grounds of the Washington Cathedral, a tranquil, walled medieval garden awaits you. Either the garden through the 12th-century Norman arch, and approach the first garden a hortalus or little garden, which is designed as a medieval herb garden. A nineth-century French font, from the time of Charlemagne, dominates the garden, which is surrounded by old English boxwood. Behind the hortalus there is a rose garden. Walking on, you find a long yew walk, starting from an ivy-covered gazebo and extending to a great yew at the east end of the garden area. Circling back to the west along the boxwood-lined paths, there are such delightful old flowers as coral bells. The boxwood along the paths is so thick that it creates a maze-like effect, and children are content to play here endlessly. On the west side of the garden is a large, shaded lawn, enclosed by a stone wall and very peaceful. Doubtless Charlemagne would prize this cool and placid garden, even if it doesn't contain his prescribed 60 flowers and plants. DUMBARTON PARK. Entrance on R Street between 31st Street & Avon Place NW. Open daily from dawn to dusk.

Undoubtedly the most secret garden is Washington, Dumbarton Park almost requires a map to get there: It is unmarked, and tucked away behind two Georgetown institutions, Dumbarton Oaks and Montrose Park. You advance upon it by skirting a formidable barrier across the road between those two gardens. Post Dumbarton Oaks' wall on the left, and on the right past Montrose Park's vine-covered tennis court with its pergola as bleachers, past the picnic tables and the boxwood, past all the people and dogs, you proceed down the road into a rather forbidding ravine. On the left, at the back wall of Dumbarton Oaks, there is a fence with an open gate, which has a "closed" sign on it. If all the reminds you of Alice in Wonderland, don't take fright and steel yourself for the Queen of Hearts Inside the gate is not just the promised secret garden, but, to our knowledge, Washington's only meadow. A brook meanders through it, and ornamental trees, dogwood, redbud and others flourish. This park's beautiful 27 acres were donated to the city by the Bliss family, the owners of Dumbarton Oaks. On a steaming summer evening, it's more than a treasure: It's the Elysian Fields. DUMBARTON HOUSE, 2715 Q Street NW. Nine to noon daily except Sundays and holidays. Closed July and August. (Headquarters of the national society of Colonial Dames of America.)

Behind Dumbarton House, a handsome Federal house filled with imposing antiques, is a lovely garden of the same period. Here traditional small greenswards edged with boxwood are intersected by gravel paths. In the garden's center is a classical "temple," with politely draped statues in its niches. A high wall affords great privacy and quietude uncharacteristic of Georgetown. Against the back wall are delightful trellised fruit trees. A large tree stands at each end of the garden, and myrtle everywhere and a few flowers help to provide a green and peaceful mis-en-scene . TEXTILE MUSEUM, 2320 S Street NW. Open Tuesday through Saturday, 10 to 5; closed Sundays, Mondays and holidays.

Past the stately facade of the Textile Museum, through the inviting galleries hung with magnificent rugs and textiles, lie not one but two beautiful gardens. The first, a formal garden behind the museum, begins as a circular garden, with overhanging wisteria. Handsome boxwood encloses a small pool surrounded by ivy. From the pool a long boxwood walk leads to a small classical pavilion at the end of the garden.

Behind the wing of the museum, next to the formal garden, a second garden catches the eye. First there is a romantic terrace, with a slightly brooding quality, almost a presence. It seems as if dancers in the moonlight might come back to waltz in the next full moon. In front of the terrace is a small court, with a quiet pool edged with myrtle. Beyond the court, brick walls enclose a magical, tree-shaded greensward, very private and dating from the last century. Here are the flowers of an earlier age: lilac; spirea; lilies of the valley; phlox and iris. Peonies and roses thrive. Towering trees shade the garden, while several small apple trees, yew and azaleas soften the garden's brick walls. LILY POND GARDEN, Library of Congress

Within the marble confines of the Library of Congress there is an improbable lily pond garden. Ou may have used the library's reading room for several years without even noticing it. Then one day, idly waiting for a slow elevator outside the reading room, you glance past the Gutenbery Bible to a window and notice some greenery beyond. Inquiry of a guard sends you on a labyrinthine path to the basement and through some unmarked doors to the garden. It's tiny, with a small lawn surrounding the lily pond, with its scholarly nature lovers are set about. On two sides of the garden. Small trees and shrubbery line another wall, and beyond is another section of the garden with an intricately designed stone pavement and pachysandra.

This gem of a garden is probably best known to those who attend Library of Congress musicales; during the intermissions, the auditorium doors are opened onto the garden. While Minerva, Goddess of Wisdom, holds sway within the library, as she gazes down from her grand mosaic, in the lily pond garden a rustic Pan presides. BOTANIC GARDENS, First and Independence SW. Open 9 to 9 daily.

If the Washington summer isn't enough for you, try the tropics at the Botanic Gardens, at the foot of Capitol Hill. No matter what the season, their sheer lushness is compelling, so it's surprising that these remain among Washington's secret gardens -- yet our survey of ten Washington denizens turned up only one who had ever been there. For flower-lovers, the Botanic Gardens offer four displays a year, as well as gardening courses.

One little-known advantage of the Botanic Gardens is their availability, with sponsorship by a member of Congress, to cultural organizations, which can reserve a reception room in the evening, and all can wander about the tropical gardens at will. AZTEC GARDEN, Organization of American States Building, 17th Street at Constitution Avenue NW. Open during daylight hours, year round.

Amid Washington's many traditional North American and European gardens, the Aztec Garden comes as a distince surprise. There, in a handsome garden, a blue-tiled pool is dominated by a powerful statue of Xochilipilli, the Aztec god of flowers. Xochilipilli's pool, with its dramatic tropical water lilies in bloom and its yellow iris, also offers goldfish and one wild duck and her brood.

Approached from the OAS building's west terrace, the garden is surrounded by a marble balustrade. On either side of the central pool are two very pleasing greens, each in the shape of a trapezoid, which avoid the sharp lines of the usual rectangle. The green plots are edged with boxwood, with ivy flourishing beyond. At the west end of the garden is an imposing building with an enclosed terrace, inlaid with Mayan carved figures. The building houses the Museum of Modern Art of Latin America.

The garden is shaded by a remarkable array of magnificent old trees, among them a sycamore, black spruce, American beech, pin oak, magnolia, blue spruce, a horsechestnut, green ash and a towering hickory. Exotic trees are to be found as well, including the paulonia, also known as the Empress of China tree. Beyond the garden proper is a small house, the oldest on the property. In the old days when Constitution Avenue was part of the C&O Canal, mules pulling barges were lodged in this building.

COURTYARD GARDEN, National Portrait Gallery/National Museum of American Art, Eighth and G Street NW. 10 to 5:30 daily.

This courtyard between two art museums is an oasis in the heart of official Washington, known mostly to arty lovers and neighboring bureaucrats. It's a shady retreat dominated by two immense American elms and two large 19th-century cast-iron fountains. Banana plants and fuschia provide an ambience of the century past, but two Alexander Calder sculptures, gifts of the artist, compete for attention.

Around noontime, visitors with lunches from the excellent gallery cafe, as well as brown-bag bureaucrats and art students, fill the tables in the courtyard and spill over onto the lawn. But should you venture down for a 10 o'clock continental breakfast or linger late in the afternoon, you will find only greenery and pigeons. HILLWOOD GARDENS, 4155 Linnean Avenue NW. 11 to 4 daily except Sunday and Tuesday, by appointment only: 686-5807.Fee: $2.

Hillwood, once the estate of Marjorie Merriweather Post, and now owned by the Hillwood Foundation is aptly named: The main garden, set on a hill, slopes sharply down to woodland below. On the horizon only the Washington Monument rises above the wood.

As you enter the garden, walking the winding road in the midst of woods, a first realization is that the only sound is birds singing: back to nature in upper Northwest. Wending you way around the house to the main garden, you will find a terrace shaded by eleven magnificent elms. To the west of the house, a French garden is enclosed by its traditional trellis. Within is the traditional formal, clipped boxwood garden. Beyond, an English rose garden with innumberable varieties is bordered on its side by an arbor hung with climbing roses. Nearby, a small greensward is enclosed by boxwood; all about are chairs for garden devotees. Down the hill a Japanese garden is tucked away, complete with tiny ponds, waterfalls, a rustic bridge and a weeping willow.

A woodland glade surrounds the various gardens, and is filled with rhododendron and distinguished azaeleas. A path leads through this bosque, graced here and there by bluebells in the spring, and it provides a long, shaded walk on a hot summer's day.

As might be expected in English and continental gardens, marble conceits abound, including small Bacchuses and a company of child satyrs piping away, as well as a young Eros. But among Mrs. Post's adult statley females predominate, with Diana the Huntress in a place of honor. Four surprising sphinxes are to be found, with the head and shoulders of a dainty 18th-century shepherdess and the body of a lion. Hillwood is a garden of great variety and no little whimsy. OLD STONE HOUSE GARDEN, 3051 M Street NW. Open 24 hours daily.

In the midst of busy Georgetown, open the picket gate of the Old Stone House and step back two centuries into the charm of a quiet Colonial garden.Adjoining the oldest house still standing in Washington (it was built in 1765), the garden once contained a kitchen garden and livestock. Now it's a dooryard planted with bright flowers near the house and becoming a long greensward at the back. Here fruit trees and shrubbery found in 18th-century gardens flourish. Apple, crabapple and dogwood trees abound, together with a crape myrtle tree and lilac and liburnum bushes.

While the garden is occasionally crowded on a sunny day at lunchtime, peace reigns the rest of the day. At dusk, or later in the evening, only the occasional sound of a guitar floats over the quiet garden.