(Decanter) - If price is any guide (and it is: expensive wine receives careful and repeated scrutiny through time), then the two greatest zones for wines based on Cabernet Sauvignon are Bordeaux’s Left Bank and California’s Napa Valley. I recently spent an unseasonally cool June week in the Napa, trying to discover a little about how its internal terroirs work — and along the way shared time with two Bordelais, Christian Moueix of Dominus and Philippe Bascaules of Inglenook. Their insights into the nature of Napa were fascinating.

Christian Moueix’s relationship with Napa stretches back over almost half a century: he loved his student days at Davis in the late 1960s (how could he not?); and he returned during the decade that followed to ‘prospect’ vineyards. The early 1980s saw him begin a joint-venture partnership, christened Dominus, with the existing owners of the Napanook Ranch (who, as it happened, were the daughters of John Daniel, the man who had inherited Inglenook), before eventually buying them out.

He gave himself time (he thought it would take 20 years to realise the vineyard’s potential), and began from two principles: the vines were to be dry-farmed, and he would never acidify the resulting musts or wines. Both were prescient. Acidification was widely practiced at the time (another grower remembered “buying tartaric acid by the pallet” in the 1980s, something he’s long since abandoned).

Dry farming in Napa, though, remains exceptional. Many insist it can’t be done on hillside and mountain vineyards, which was one reason why Christian Moueix prospected only the benchlands and alluvial fans on the valley sides. Is this true, though? Annie Favia of Favia Wines, a viticulturalist whose long experience was formed with David Abreu and others, is just one who believes that dry farming is possible anywhere in the Napa, provided that the vines are acclimatized early, and provided growers are prepared to adjust their expectations about how much, and how quickly, the young vines will yield.

The practice at Dominus, in fact, is to deep-water the vines a couple of times per summer in the first and sometimes second year following planting, to ‘train’ the roots to search for water, but to stop as soon as their fruit passes into production. The only other water the vines receive is a rinse to remove dust shortly before harvest, and most of this water evaporates swiftly afterwards.