Two years ago, I donned my hiking boots for a “Down & Dirty” session at the Trefethen Family Vineyards during the Professional Wine Writers Symposium at Meadowood in Napa. In truth, there wasn’t much dirty work involved, other than a pruning session (unless you count my rummaging through the bone pile under an owl nesting box where I’d spotted a well-preserved vole skull, which I carried home to my country-boy husband like a cat with a prize).

Mostly I toured and tasted—no work gloves required. I trailed agronomist Brendan Brambila through the vineyards, getting an earful about everything from Napa history to vineyard management. I drank Napa Riesling by an antique gazebo together with the founder’s dynamic granddaughter, Hailey Trefethen, then sampled the rest of the portfolio while winemaker Bryan Kays detailed the backstory of each wine.

The Trefethen wines are much to my taste, showing an elegance and restraint that reflects both the cooler Oak Knoll District climate (touched by San Francisco fog) and the winery’s philosophy, which aims for balance.

So naturally, when the opportunity arose to attend a tasting of their library wines, I jumped at the chance. It’s not often that you get to taste 40-year old Napa chardonnay. Not many exist; in the 1970s, the industry was still so new that it never occurred to anyone to set aside bottles. But the Trefethens held back a few, and they’re sharing these with journalists and industry this year in celebration of the winery’s 50th anniversary.

In 1968, Eugene Trefethen bought a crumbling old winery on Highway 29 called Eshcol, designed by a Scottish sea caption in 1896. The retired Kaiser executive was looking for a place to farm that had strict environmental regulations, and he’d set his sights on six other farms as well. But he told the land owners that his purchase was contingent on the passage of the Agricultural Preserve bill, then under debate. So the farmers lobbied for it. “I think that had an impact,” Eugene’s personable daughter-in-law, Janet Trefethen, said at the tasting. The bill passed, and Eugene had his 600 acres of farm land.

“We’re the only winery in Napa over 45 years old that has grown every single grape that has gone into every single bottle,” Janet noted with pride.

Eugene had planned to sell the grapes, but his son, John, had other ideas. John and Janet produced the family’s first wine in 1973—at a time when there just were a mere two dozen wineries in Napa. “We’d read that the French put their wine in oak, so we thought we’d try that too,” Janet recollected. But there was no place to buy wine barrels in California, “so we went to Bardstown, Kentucky, and bought five bourbon barrels.” It was a disaster. The chardonnay came out pink and smelling of bourbon. The wine was tossed.

But by their third vintage, John and Janet were off and running. Cementing their status as serious winemakers, they won “Best Chardonnay in the World” at the 1979 Gault Millau World Wine Olympics in Paris, a rematch of the famous 1976 “Judgment of Paris” that put Napa on the map.

Their prize-winning 1976 vintage wasn’t served at last week’s tasting, but the 1977 was. “So many people don’t think Napa Chardonnay ages—and some don’t,” said Janet. “But my favorite is here in its ball gown.” Honey-gold in color, with the scent of pineapple and honey, this 41-year-old wine was amazingly fresh and lively, bursting with flavors of pineapple, ripe juicy pear, and toasted hazelnuts. It was bright, complex, and lip-smackingly good.

The chardonnay flight also included the 1985, 1991, 2005, 2011, and 2016; a refreshing acidity marked them all. The latest vintage was my other favorite: a bright potpourri of mango, pineapple, and lemon curd with a dab of biscuit. It was lively and gorgeous. (Janet also confessed her preference for this and the 1977.)

Another wonderful library wine was the 1988 Riesling. Going against the trend for sweet Rieslings in 1980s Napa, theirs was dry from the start. And this 30-year-old bottle showed it ages with the best of them. It was still zesty and alive, even as it displayed the oxidized honey-nut notes of a mature white. (If wishes could be granted, I’d be drinking this every day.)

The cabernets were vintage 1979, 1986, 1999, 2006, 2011, and 2015. One could taste when malbec and petit verdot joined merlot in the blend. (By law, the wine must contain at least 75 percent Napa cabernet to be labeled as such; this flight ranged from 79 to 91 percent.) The classic, dusty side of Napa cab was seen in the 1986 and 1999, while the 2006+ wines were more fruit-driven. (This, of course, also reflected differences in maturity.) “There were two inflection points,” explained Lorenzo, brother of Hailey. “1999 was about replanting the vineyard for optimal light exposure. And in 2006 we introduced the new varietals,” planted in 2000. Unlike many areas of Napa, “malbec grows well at Trefethen,” Lorenzo noted. “It brings an up-front jamminess.”

“In the 1990s, we went nuts with experimenting,” Janet observed, referring to Napa as a whole. “We tried everything. You captured flavor, but you got high alcohol. Now there’s a definite effort to level off.”

“We were increasing ripeness without getting more flavor,” Lorenzo added. He pointed to their use of oak as well, which ramped up, then ramped back down over the past 40 years. “We’re getting smarter and better. It goes back to the idea of balance.”

Amen to that. And Happy Anniversary, Trefethen!