A lot goes into making a delicious wine. The soil, topography, weather, pruning, irrigation, time of harvest, tannin content, lees content, and fermenting temperature all have a hand in making a good batch of wine—and one misstep can make a crop go bad. It’s no surprise, then, that it’s hard to pinpoint exactly what makes wine from Napa Valley generally tastier than wine from, say, Kentucky. But two components are key: soil and climate.
Dig around your back yard, and you’ll see that the dirt can be patchy. Some areas have silky topsoil. Others are awfully rocky. If you had a chemistry kit, you’d also notice that the pH, calcium, and iron contents can vary wildly, too. All of this affects how grapes grow. The calcium, iron, and pH all influence photosynthesis. Meanwhile, soil supports the roots and controls how well water drains, which determines how much nutrients and minerals the grapevine soaks up.
Soil doesn’t control the wine’s taste, though. Research shows there’s no link between the mineral content of the grapes and the mineral content of the soil. Rather, dirt quality influences the health of the grapes. In the world’s best wine regions, the soil’s capacity to hold water is just right. That means a better chance of growing quality grapes.
It doesn’t stop there. Rain and temperature can really make or break a wine. Even in places with amazing soil, a year of weird weather can turn a crop with amazing potential literally into bitter disappointment. Consider the Bordeaux region of France—the 1990 vintage is fantastic, but the 1991 batch is dismal. That’s because, in just one April night, frost wiped out half the grapes in 1991, a loss of $715 million. (Crafty viticulturalists nearby saved their grapes by flying an air-warming helicopter over the vineyards.)
The best wine regions have consistent climates. Spring is warm with easy rain. Summer is hot, cloudless, and relatively dry. Autumn is more like an Indian summer, and sparse rain becomes the ticket to a good harvest.