Tuscany's olive trees have endured for centuries, bearing fruit that is pressed into what some consider the world's best extra-virgin olive oil. Until last winter. In January, the worst freeze of the century brought snow drifts and frigid temperatures to this central Italian region, so accustomed to kinder treatment by the elements.

Spring turned the hillsides green once again, and the irises and wisteria bloomed as usual. But against this backdrop of foliage and flowers stood the gnarled, leafless olive trees, stark reminders of the freeze. La Nazione, Florence's main newspaper, compared the appearance of one such grove to a petrified forest.

By early summer, a report by the regional government confirmed everyone's greatest fear: A full 90 percent of Tuscany's olive trees had been damaged severely by the freeze. At best, recovery will not be complete for four to five years -- and during that time, production of the region's incomparable olive oil will dwindle to nearly nothing.

The 1984 olive harvest was mostly in when the calamity struck. Only late this year, when farmers and commercial producers would normally gather the crop, will the shortage begin in earnest. But panic is already in the air, for cooking, to Tuscans, is unimaginable without a liberal supply of extra-virgin olive oil. It is as much a staple as the region's coarse, saltless bread and famous chianti wines.

"Olive Oil Prices Climb to the Stars" and "No Tuscan Olive Oil for Four Years" blared the headlines. The region's agricultural experts play down rumors that the price per liter for extra-virgin oil will climb to 46,000 lire (about $25), but no one can be certain it won't. Already Tuscans are paying double or triple 1984's base price per liter of 4,800 lire (about $2.50). Although producers remain well stocked with oil that was pressed in 1984, some are holding back part of their supply in anticipation of higher prices.

Extra-virgin oil from Tuscany has a small but tenacious foothold in the American market, where it joins prized oils from Provence and another Italian region, Liguria, on the shelves of specialty shops. So far, the supply and prices of Tuscan oil have changed little, according to several Italian delicatessens in the New York and Washington areas.

"We have a long-standing relationship with our suppliers, and so far the prices of the oil they supply us with have not fluctuated much," reported Eugenio Pozzolini, co-owner of Dean & DeLuca, a New York City firm that imports three estate-bottled olive oils from Tuscany.

Piero Stucchi-Prinetti will be cautious about raising the price of the extra-virgin olive oil produced on his Tuscan estate, Badia a Coltibuono, for export to the United States. "It would be a mistake to alarm the market. In the fall, we must analyze how much product we will have and prepare the market for prices to go up," he says.

Even with this low-key approach -- which he hopes will be shared by other producers -- Stucchi-Prinetti expects the price of Tuscan oil sold in the United States to rise at least 10 to 20 percent by the end of 1985.

In talking about the dismal state of the olive trees, Tuscans refer invariably to two previous freezes, one in 1929 and the other in 1956. Despite apparent devastation, many oil trees recovered and began to bear again. But the damage seems to be worse in the most recent freeze. Temperatures dropped lower, the bitter cold persisted longer and many trees were not yet dormant -- conditions that combined to do maximum harm.

A drive south from Florence into the chianti country, an area reputed to produce the best Tuscan oil, reveals grove after grove of barren olive trees. Located west of Florence near the Tyrrhenian Sea, Lucca is another important olive-growing area. There, temperatures during the freeze never dropped as low as in the rest of Tuscany. When the trees put out new growth in the spring and began to bear fruit, growers breathed a sigh of relief -- prematurely, as it turned out. In July, six months after the freeze, Lucca's olive trees finally succumbed to its effects and began to die.

In November or December, growers throughout Tuscany normally gather their olives; the first pressing, with no chemical treatment, creates the rich greenish gold liquid classified as extra-virgin oil. In her book "The Feast of the Olive," Maggie Blyth Klein praises Tuscan extra-virgin oils for "their clean, strongly fruited flavor, their pepperiness and their so-called rustic qualities."

Pozzolini says the "lighter, rounder character" of Tuscan oil sets it apart from the competition.

Ironically, the very climate that puts Tuscan olive trees at risk accounts for the special quality of the oil. Tuscany is located about as far north as olive trees will grow. Here, olive production is sparser than in Apulia and other Mediterranean regions, which supply the bulk of the world's olive oil. Instead, Tuscany's cooler climate combines with rocky terrain to nurture olives that, when crushed, exude a less fatty, more flavorful oil than can be found farther south.

From government officials to peasants, Tuscans share the sentiment of a newspaper report describing the damage to the olive trees as a blow "to the patrimony and tradition of Tuscan agriculture." The olive disaster also will have more tangible results. According to the latest estimate by the regional department of agriculture, losses in production will total 350 billion lire (about $190 million) over the next four to six years. Restoring the olive groves to their former condition would require an additional 200 billion lire ($108 million).

Even before the freeze gave cause for these gloomy financial projections, production of extra-virgin oil had been on the decline for several decades. It is considered a marginally profitable endeavor because labor costs are so high, amounting to about half of the oil's total cost. Production methods have changed remarkably little since the time of the Romans. The olives for the finest oil are gathered painstakingly by hand or with a small rake, crushed in a heavy, primitive press, then stored in ancient clay urns known as orci until bottled.

Olive trees have been linked with grape vines for centuries. The two used to be literally yoked together, with the olive trees planted at intervals between vines as support. Now, in an economic sense, it is the vineyards that support the olive trees. One simply doesn't see independent olive operations in Tuscany; instead, wine producers grow olives as a sideline. If the olives become a financial liability, they cease to be harvested. The added burden of recovery from the freeze could persuade many growers to give up.

A few growers have already pruned their groves so severely that only two or three main branches protrude from the trunk -- creating a sight one observer compared to the rows of crosses in a cemetery. Most growers are waiting until late summer to see whether the trees send up new shoots at the base. Even trees that show such signs of revival, however, would need years of growth to become productive again. Soon the time will come for a tough decision: to replant or not, and if so, how?

This is not an obscure, local agricultural matter. It has become a public policy issue of broad interest, a heated debate in which growers, government officials and consumers all have a say -- and rightly so, because the tab for repairing the damage will be shared. Although growers will absorb some costs, they are expected to receive aid in the form of grants and loans from sources that include the regional government, the national government and the European Economic Community.

The head of Tuscany's agriculture department, Ilario Rosati, has advocated going beyond simple restoration to undertake "a modern cultivation of olives." Under such a policy, preference in allocating financial aid would go to producers able and willing to improve production rates and thus reduce costs. Trees would be replanted only in flatter, more accessible areas. Growers would replace olive trees, many of them planted several centuries ago, with new, faster-maturing strains that are somewhat closer to the ground.

Such proposals are made with an eye to southern Italy, where some growers have turned olive cultivation into an attractive business enterprise through mechanized harvesting of low-growing trees (sometimes using nut-harvesting machines imported from California).

The desire for improved efficiency is mixed with anxiety about tampering with a system, however labor intensive and troublesome, that has yielded superlative oil through the centuries. Automation would cut labor costs, everyone agrees -- but then the objections begin. Tuscany is too hilly for the machines to be practical, the vigorous shaking might harm the trees, and any olive that will fall off merely by being shaken must be overripe.

As they ponder the future of olive cultivation in Tuscany, producers who have penetrated the American and European markets also worry about the prospect of seeing their product vanish for several years.

"We're committed to serving our clientele -- and to holding our place in the market," says Stucchi-Prinetti, whose extra-virgin olive oil has been sold in this country for the past decade. "We were the first to put extra-virgin oil in a beautiful bottle and to market it carefully. It was a gamble, but the results show that customers are prepared to pay for a product of recognized quality."

Like other well-established producers, Stucchi-Prinetti has a contingency plan in the event of a meager olive harvest on his estate. The company will buy the best olives possible -- within Tuscany, if possible, or going as far afield as the Marches and Umbria -- then press them and blend with any olives harvested from the estate. The label would read "Selected and blended by Badia a Coltibuono," although regulations do not prohibit making oil from olives grown in different regions of Italy.

A single bad winter, then, has set off a chain reaction in Tuscany's olive oil industry that could lead to lasting changes in production levels and methods of cultivation. Admirers of Tuscan extra-virgin olive oil can only hope that its quality, if not quantity, will remain stable in coming years.

Even more painful to contemplate is the potential change in the Tuscan landscape, which owes much of its charm to the dusky gray-green leaves and twisted branches of the olive trees. If widespread predictions prove to be true -- that up to half of the olive trees will be dug up and not replaced -- the appearance of the Tuscan countryside could be transformed forever.