Rick Gamble's truffle dinner won't be possible for at least two years, even though he started planning it three years ago when he potted an oak sapling on the windowsill of his Annapolis home. The tree is seeded with Tuber malanosporum, the black truffle--truffe in French--which grows in symbiotic relationship with oaks and filberts, in the ground near their roots. While French truffles the size of golf balls--looking like spongy charcoal covered with thousands of tiny diamond-shaped formations--sell for $250 to $500 a pound, the tree Gamble planted on a whim cost merely $8 from a truffle farm now located in Dripping Springs, Tex., which could become the truffle capital of the New World.

"The truffe, the whole truffe and nothing but the truffe," says the T-shirt of Franc,ois Picart, who runs the American branch of Agri-Truffe, the company that grows those saplings and ships them around the country, mostly to farmers more serious about them than Gamble is. As enthusiastic as a truffle pig in a Bordeaux oak forest, he told his story to a meeting of the Mycological (pertaining to mushrooms) Association of Washington this spring when he passed through on his way to help out in his family's restaurant in Paris.

At the beginning of the 20th century, France's annual truffle production amounted to nearly 2,000 tons, but now, in the aftermath of wars and urbanization, worldwide production has dropped to less than 100 tons, half of it in France. In 1966 the French government addressed this crisis by assigning the Institute de See TRUFFLES, E16, Col. 3 TRUFFLES, From E1 Re'cherche Agronomique to research the problem. Four years later the group developed a technique of seeding the black truffle, and production was started by a company called Agri-Truffe, which eventually expanded into the United States, particularly to California.

Franc,ois Picart was already trying to develop the snail business in California, and was inspired by that state's oak trees to think about truffles. Pursuing the subject in France, he was directed eventually to Agri-Truffe near Bordeaux, and three years ago brought inoculated trees to the U.S.

They were confiscated at the border.

So then he brought seeds for the trees and the spores for the truffles, which passed through customs, to California. Next he researched growing sites. In one location the soil was suitable but the land was too expensive. Oregon's climate was right but its soil wasn't. Nevertheless, people from Oregon--as well as Washington, Massachusetts, Ohio and even North Carolina, where six acres were planted--were ordering his seedlings. In all of these places, said Picart, the soil had to be chemically changed to suit the truffle.

Then a man ordered a dozen trees to plant in Texas, and answered Picart's incredulity with a very convincing argument for Texas' hospitality to the truffle. A year and a half ago Picart went to Texas himself and took soil samples for his French analysts, who declared the soil just right; the pH must be alkaline, 7.2 or higher, the soil calcareous and the ground well drained (Camp David also sounds appropriate, suggested one mycologist). There must be about 30 inches of rain, but at the right time, and there must be enough change of seasons to allow a dormant period. Too much rain in winter, or freezing, makes the truffles difficult to dig up, since winter is their harvest season. But some climatic deficiencies suit the truffle just fine: poor, shallow soil forces the trees to depend on the truffle, and Texas' summer storms are ideal for shocking the truffle spores into fruiting, added Picart. So in June 1982 Picart closed down his snail operation and moved to Texas, where there were already elusive white truffles growing wild.

Oil-rich Texas hardly needs another luxury resource, but black diamonds, as this most valuable of truffle varieties has been called, may join black gold on that state's product list. The effect on the truffle market, even if the experiment is successful, won't be felt for 20 years, explained Picart. He is producing 20,000 trees now, and orders are coming in by the thousands, though mostly only enough for one- to five-acre plots.

While it will be another three to five years before Texas truffles could be a reality, some of Agri-Truffe's earlier sales are closer to bearing fruit. Around the fifth year of Tuber melanosporum's development the weeds around its host tree start dying as the fungus kills its competition. This "burnt out" or brule'e area, as it is called, means truffles should be ready within the year; one planting in Massachusetts is reported to be at that stage. Truffles already grow wild in some states, and Oregon's white truffles are appearing on menus in major cities, though they have very little flavor.

Picart now sells his mycorrhized (seeded with spores) trees for $10 to $14 each, and stocks filberts as well as oaks. To set up an orchard for truffles and maintain it for the first five years costs somewhere between $3,000 and $6,500, said Picart, and the first harvest isn't for seven years. "That is the financial definition of a tax shelter," said Rick Gamble, who doesn't seem too concerned about the cost of his potted truffle orchard and has only fantasies of harvesting a potted fungus. The hope of a truffle farmer is to harvest a quarter of a pound to four pounds of truffles per tree, or about a hundred pounds an acre. And to gain from the increased value of the land as well.

Growing is only half the problem. Harvesting truffles is a special challenge, for they grow 1 to 1 1/2 feet underground. Thus the problem is finding them. The options, according to Picart, are ripping up the tree, roots, fungus and all(which has obvious disadvantages); infesting the field with certain flies that come to rest on the ground above truffles (U.S. customs won't allow the importing of the flies, and the method doesn't work on a windy day); training pigs to root them (pigs love truffles, and you have to fight a 200-pound pig for them) and training dogs to sniff them (training either animal requires a supply of fresh truffles for the lessons). There is talk of truffle-detecting machines, though traditionalists sniff at them as unromantic.

"The major problem in commercial truffle production," says Picart, "is that people come and steal your truffles." From the buyer's point of view, a major problem is that in France the all-cash sales are conducted so rapidly that the buyer often pays truffle prices for the dirt caked around and in the fungus.

While nobody could imagine a problem in selling truffles anywhere, the United States is not the most natural market. As Picart put it, "It's a fact that there are more people in the United States who have seen a moon rock than a fresh truffle." In Washington, the home of the moon rock, that is certainly true; besides, the local soil lacks the limestone crucial to truffle culture, and climatic conditions just don't make this a prime truffle neighborhood. What to do? Says Picart, "Buy land in Texas."

Should you reap the benefit of a truffle harvest, here are some of Picart's hints for handling the fungus:

* Truffles can be stored in the refrigerator three to five weeks, or preserved in armagnac or cognac to cover, in sterile glass jars.

* Scrub truffles with a vegetable brush under a stream of clear water, since soil clings to the cavities.

* Pare washed truffles with a sharp knife, taking care to follow their irregular shape. Set aside peelings for use in sauces or for flavoring other dishes; or insert bits of peel under the skin of a poultry breast or leg; or combine with cream cheese and stuff in cavity of poultry before cooking. Also save any water used to blanch truffles, for its flavor can be imparted to soups and sauces.

* Do not peel truffles if they are to be used chopped, diced or sliced.

* Cook truffles with gentle heat and in closed containers (or stuffed inside meats or poultry) so that their flavor is not dissipated.

* Truffle flavor is best captured by cooking in some fatty substance such as cream, butter or fatty meats.

* Cook truffles just before serving, or their flavor will be lost.

* To stretch the value of a truffle, place one or two truffles in a sealed container with a dozen eggs in the shell. Store in the refrigerator at least 48 hours; the eggs will have absorbed a truffle flavor. Or store truffles in a closed jar of rice until the rice has absorbed their aroma.