Winemakers can make good, balanced Zinfandels at under high-test levels of 15 percent alcohol any day of the week, according to one Napa Valley producer. The marketplace, he asserts, only has to ask for it.

That same winemaker, who sells his wines from individual blocks because he puts great stock in the notion of terroir, also believes that it’s clonal selection, as much as site, that determines how a wine might taste.