CALL IT CROSS-CULTURAL pollination. John and Kathy Loughran, who returned to the United States in 1978 after 30 years in the diplomatic service, have taken a gracious 18th-century West Virginia farmhouse and a m,elange of objects from their years of travel and have combined them to achieve a rare retreat.

The four-bedroom house is a visual delight: textured African baskets overflowing with delphinium blossoms; an antique American pine dough box topped with a basket of Somalian ostrich eggs; blue and white Moroccan ceramics next to French copper pots; a hat rack in the family room with international headgear: a Moroccan fez, Texas cowboy hat, Gambian hat and a Saudi Arabian headdress.

John Loughran, former U.S. ambassador to Somalia, also served in London, Paris, Bonn and the African countries of Liberia and Senegal and The Gambia. The Loughrans and their three children have lived in houses of all shapes and sizes all over the world. But when they returned to Washington from Somalia in 1978, they wanted a special place to call home, a place to have a garden, a place to gather with family and friends.

They had decided to keep a small Georgetown apartment, where they would work on their Foundation for Cross Cultural Understanding, a non-profit organization promoting intercultural insight.

In 1981, they found a rambling farm house with four fireplaces, graceful double-decker verandas on the back and 10 acres of land in the hills of West Virginia with a host of outbuildings: a big barn, milking parlor, horse barn, two corncribs, a pigsty, shed and chicken house.

The house had been neglected for several years and the Loughrans hired Michael Taylor to bring it back to life. Taylor is a custom builder from the Sheperdstown, W. Va., area who specializes in expert renovation and restoration of old homes.

Determined to keep the well-seasoned character of the house, Taylor removed a superfluous Victorian porch and dormer that had been tacked onto the front. The original German poplar-wood siding was repaired and repainted, and the double verandas restored to their former elegance. A pool was put in and the chicken house was resurrected as a pool house. Landscape gardener Peter Wilson planted trees and shrubs.

Meanwhile, the Loughrans were plotting their garden, a lush 60-by-100-foot design with raised beds and walkways and plantings of herbs, flowers and vegetables.

Furnishing the house was no problem. "We had almost all we needed from 30 years of collecting all over the world," says Kathy Loughran, who is an artist with an eye for color and texture.

The hub of the house is the spacious kitchen, with its custom hardwood cabinets holding jars of homemade raspberry jam, zucchini chutney and brandied peaches. There is a central pine work table, commercial stove, stone fireplace and an antique oak harvest table.

Meals are always a festive occasion. Unlike the place cards and silver service plates of diplomatic affairs, entertaining here is a hospitable and informal event and the place is usually packed with children, friends and visiting scholars.

"We didn't want a formal dining room. We wanted to do away with all those formalities and be as simple as we could. The whole point of the country is to simplify your life," says Kathy Lough the former dining room is now a family room with French doors open porch. The lower veranda is full of wooden chairs and benches from flea markets, all painted in Kathy Loughran's favorite shade of cornflower blue. The adjoining parlor, more formal, is decorated elegantly in antiques and is used primarily for holiday gatherings.

Upstairs, each of the four bedrooms is filled with comforts and niceties: embroidered European square pillow shams piled on antique four-poster beds, freshly starched linen dresser scarves, little bouquets of flowers. In each bedroom Taylor built in wainscoted wardrobe closets and porce- lain wash basins. The upper veranda, with its fresh white wicker and chintz cushions, offers a stunning view.

The Loughrans spend as much time at the house as their schedule allows.

"We are city people born and bred," says John Loughran. "But what does a Foreign Service family do? They live like nomads. A house like this was always in the back of our minds, a dream. This house gives us roots."