We must first examine the factors that make one vintage better than another if we are to better understand vintage variability. The goal of vintners throughout the world is to harvest a crop of healthy, perfectly ripe grapes that will yield aromatic, flavorful, and well-balanced wines. In a perfect world, the cycle of grape growth and ripening occurs without interruption. The vines emerge from winter dormancy in the spring as the sap begins to circulate in the vine. Then the buds, which formed during the previous year, break out of the branches of the vine and begin to form new shoots and leaves, starting the photosynthetic process that allows the plant to convert sunshine into grapes. After budbreak, flowering occurs. Vitis vinifera vines are self-pollinating so they don’t require bees for pollination. Following that, grapes form and begin to grow. The growth proceeds through the summer until veraison, when the grapes soften and change color and the sugar content of the grape juice rises as the acid levels fall. Ultimately, the perfect balance between sugar and acid is achieved and the grapes are harvested and winemaking can begin.
That’s all quite simple and sequential, but in the real world, there are many potential pitfalls along the way. Early season frosts can damage a crop by destroying the new leaves and shoots of the grapevine. A severe frost in April of 2021 devastated many vineyards in Bordeaux, Burgundy, Champagne and southern France. Predictions of an overall 25% drop in production across all French wines will result in the lowest crop since 1970. For a winegrower, that means a 25% drop in income – a pretty significant hit on a budget. Frost is a constant concern even in warmer areas. Severe frosts in Chile in 2019, New Zealand in 2020, and even Paso Robles in 2011 caused significant crop damage and point to the universal nature of frost concerns.
Even if frost is not a problem, bad weather at the time of flowering and pollination can result in poor fruit set and also have a dramatic impact on the amount of fruit vines will produce. Excessive wind, rain and cool temperatures can all affect fruit set, resulting in flowers falling off – no fertilization and no grape formation (coulure to the French) – or in poor fertilization where small, seedless berries form but develop and ripen unevenly (millerandage).
Excessively cool or hot temperatures at any time in the growing season can affect the health of the vines or the rate at which the grapes ripen. Excessive rainfall or humidity can wreak havoc with vine and fruit health by encouraging mold growth. Hailstorms can capriciously destroy a harvest by stripping vine leaves and rupturing grape berries. Insect-borne vine diseases can also attack vineyards during a growing season and have a significant effect on the quality and/or quantity of the harvest.
If the growing season is normally good and if the grapes are healthy, the winemaker approaches the harvest with a great deal of anticipation and anxiety. The weeks immediately before the picking of the grapes are a critical time. The weather patterns preceding the harvest can ruin a potentially promising crop or resurrect the quality of a problem vintage. Ideally, the weather is moderately warm, sunny and dry and the grapes can be picked at optimum ripeness. Rain at harvest can swell the grapes with water, resulting in pleasant, but soft and dilute wines. Excessive humidity and heat can encourage the growth of molds and result in rotten grapes that must be sorted out if quality wine is to be made. Extreme heat alone can accelerate the ripening of grapes to the point where pickers cannot harvest them fast enough. The result here is overripe, excessively alcoholic wines. Cold weather at harvest can retard ripening and result in tart, thin wines – and these are just some of the problems vintners confront.
In any winegrowing region, however, there are winemakers more adept at dealing with some or all of the viticultural and vinification problems they face. We are constantly surprised at the quality of the best wines produced in so-called "off" vintages. Astute wine buyers will benefit by giving these unheralded vintages a close look, since the prices of the wines are frequently far lower than those of more highly praised harvests. In Bordeaux, for example, one can find fine quality and remarkable value among the 2014 wines — a vintage that suffered from bad press as well as difficult climate. Let your own palate be your guide rather than a simple vintage assessment that, by its nature, can only give a rough approximation of quality. That way you can get good wines and save money too.