Pham Tran has transplanted his garden from Saigon to Springfield in Fairfax County. "I have a little bit of Vietnam here," he says, pointing at his neatly arrayed, carefully mulched, 6-foot-wide beds of vegetables along the fence of his 50-by-50 foot back yard. Tran, a journalist working for the Voice of America, has a degree in horticulture and has tended a garden ever since he can remember.

He grows Vietnamese lettuce (a leaf lettuce that he says produces twice as many leaves as American varieties and does not bolt until July), an oriental eggplant (only about five inches long "but much tastier than the American giants"), edible chrysanthemum (good in salads or as a cooked vegetable) and several other kinds of vegetables grown commonly in Vietnam and which can be eaten raw or cooked.

He cherishes a 3-year-old pepper plant that he has been taking inside for the winter. "It is extremely piquant," he says, then quotes a Vietnamese proverb: "A pepper must be as hot as a woman is jealous."

He is especially proud of his patch of a salad green that also can be cooked: It is called rau muong, usually translated as "water convolvulus." (The French name is liseron d'eau.) "It's a delicacy," Tran says, and it is selling for more than $2 per pound at Vietnamese supermarkets on Wilson Boulevard in Arlington.

Several stores in that section, known as Little Saigon, sell seeds of Vietnamese vegetables. The seeds come from Evergreen Y.H. Enterprises, in San Jose, Calif. 95160.

Tran grows three kinds of Vietnamese calabashes, which he says start bearing fruit after only 40 days. He calls them "Vietnamese squash," but they look exotic enough to be designated by the Kipling-esque term of calabash. "You can cook them like zucchini," he says, "or add it to chicken soup. Or make candy out of them."

His three calabashes are: bi xanh (the shape of a traditional watermelon, about 20 inches long and 7 inches wide), bau dai (longer and thinner than bi xanh, and a prolific plant) and bau tron (shape and size of a cantaloupe).

His favorite is bi xanh--"my target vegetable," he calls it. Last year he harvested about 50 of them, and the heaviest weighed 25 pounds. He keeps them in a cool, fairly well-lit place in the basement. "You mustn't expose them to heat or darkness," he says, "or they will rot."

He mulches all his vegetable beds with pine bark about two inches thick; he says he saves one-third on his water bill that way. He has improved his soil with peat moss, sand and cow manure. He considers horse manure "too hot" and believes that a rich soil makes insecticides unnecessary.

He says he never plants the same vegetable in the same place in two successive years. "I move them every year," he says. "I have them on a merry-go-round." He laughs. "If you keep vegetables in the same place year after year they do not grow big fruits. Like people, vegetables too must travel."

He came to this country after the fall of Saigon in 1975. He started gardening the following year, first in a friend's garden, as a sharecropper, on a 50-50 basis. A year later he moved into his present home where he began a vegetable garden right away. His first calabash seeds came from a Vietnamese friend who had been living and gardening in Florida for many years. But the friend, overwhelmed with requests from refugees, could send him only four seeds.

Fortunately, each calabash yields dozens of seeds, and from his first harvest on, Tran has been able to send seeds to other Vietnamese who were starting gardens in the United States and Canada. "Every Vietnamese has a lot of relatives and friends," Tran says, "and every Vietnamese tries to grow some vegetables, even if on a balcony."

Bi xanh stays fresh for at least four months, but this year he has one he picked in September and has wintered over--still good after nearly nine months!

The other two kinds of calabashes do not keep as well, he adds, but they are more prolific. Last year he had up to 100 bau dai.

Asked what he does with such an abundance of calabashes, Tran smiles. "I distribute them among friends," he says, "particularly at the lunar new year, which comes around February. Bi xanh is a perfect present. Vietnamese people love to taste it. Or just to look at it. It is a souvenir of Vietnam."

That lunar new year is Tet--remembered in this country after the famous Viet Cong offensive. Tet is Christmas, Halloween and New Year rolled into one, Tran says, and it is a time for visiting family and friends, and for exchanges of gifts.

"Vietnamese people are very careful in selecting the first person to cross the threshold of one's house on Tet," a friend of Tran's explains. "That person has to be happily married, with at least one child. He doesn't have to be prosperous, but he must have a stable job. He must have a good disposition. Above all, he must be a happy man."

In the eight years that he has lived in this country, several Vietnamese families in the area have asked Tran, now 46, with a wife and five children, to be that first guest.

He always brings a calabash.

Starting July 21, look for Charles Fenyvesi's column on Thursdays in Washington Home. Beginning July 24, Henry Mitchell's Earthman column will appear on Sundays in Style.