As a restaurant-based sommelier for the past ten years, working with wine lists of up to 2,700 selections, I spend a good portion of my time answering guests’ questions about individual wines. “What does this wine taste like?” “Which of these is a better vintage?” But I also get to field questions about wine in general. One of the most common questions is “Why does this wine cost so much more than this other wine?” There are numerous factors that go into a wine’s pricing in the marketplace, but perhaps the most important is the Y Factor, which is the yield.

The yield is the quantity of grapes that each vine produces, and thus the amount of grapes, usually expressed in weight, that a particular vineyard produces in a particular season. Throughout the growing season, both the winegrower and Mother Nature make significant contributions to how this turns out at harvest time.

Toward the end of winter, vineyard workers, or in some cases automated machinery, will complete their yearly pruning. By pruning vines in a way that limits their potential for grape growth, vintners can exercise great control over the potential yield of the vineyard. Why would a vineyard owner choose to grow far fewer grapes than is physically possible? By ensuring each vine has a limited number of grapes on it, the grower forces the same amount of resources into a smaller number of grapes, thus adding more character to them. Many of the world’s highest-end wines are produced from vineyards that are purposefully pruned to produce a small yield. Economically, the vintner is able to make up for the lack of quantity by charging a premium for the resulting high-quality product.

Mother Nature can be kind, but can also be brutally cruel. Soon after pruning, during a period called “budbreak,” small shoots will begin to appear on the vine in March or April in the northern hemisphere. A frost during budbreak can be devastating to yields. In 2017. in Bordeaux, one of France’s premier fine-wine regions, a late spring frost swept through the area at the end of April. Overall, the large region lost 40 percent of its potential crop, or the equivalent of 1.6 billion euros. Some unlucky estates reported losses of 100 percent when the frost decimated every single one of the delicate new shoots in their vineyard. Humans can try defensive methods, such as lighting fires, spraying water to form a protective layer of ice, or even blowing cold air away with a helicopter, but in the end Mother Nature has the last say during these extreme weather events.

Flowering will occur a couple of months after budbreak. The vines are especially susceptible to foul weather at this time. Cold, wind, and rain can all reduce the number of flowers that will remain on the vine to become grapes. In 2015, in Santa Barbara, cold and windy weather during flowering ensured that the upcoming season would result in a much smaller crop than in previous years. This situation was further exacerbated by the drought conditions across the entire state at that time. A lack of available water leads to smaller grapes with less juice inside. This often results in a more concentrated wine for the consumer to enjoy, but less wine for the producer to sell. This financial shortfall can be mitigated by charging more for the wine in such a year compared to previous years, but in general the marketplace will only support limited increases in price when imposed suddenly. After all, most wine drinkers aren’t tracking the weather in their favorite wine regions throughout the growing season.

To combat drought, the winegrower can use irrigation to try to avoid a decrease in yield. Almost all vineyards in California are irrigated to some degree, while many European wine regions actually prohibit irrigation entirely as a means of ensuring that wines from the area are not overly diluted. However, local authorities will on occasion make a temporary exception to the rule in order to ward off the potential economic hardship that would be felt by growers should their grapes shrivel on the vine in unusually hot, dry weather.



Towards the end of the growing season, some vineyard owners will engage in “green harvesting.” This is the practice of going through the vineyard and cutting off any clusters of grapes that look to be less ripe than others and dropping them on the ground. This can greatly reduce the yield, but it also reduces the competition among the remaining bunches as they fight for the resources needed to push their ripeness to the maximum level during the final few weeks of summer.

Rain just before harvest can result in an increased yield of somewhat diluted grapes. Windy conditions prior to harvest can remove water from the grapes, increasing concentration while decreasing overall yield. Because vineyard yield and grape quality usually have an inverse relationship, when Mother Nature is the force that produces a small yield, it is often a great result for the consumer, who gets to enjoy a very high quality wine without paying a huge premium. On the flipside, the producers who are affected will take the financial hit as they wait for next season, hoping for a bumper crop. This inverse relationship is also the reason that a vintner intending to make a premium wine may utilize methods such as severe pruning, limited irrigation, and green harvesting to farm a vineyard that will produce two tons per acre, while a vineyard growing grapes for a more ordinary wine may yield ten tons per acre. This large variance in the Y Factor illustrates why it plays a key role in both wine quality and wine pricing.

It should also be noted that many growers take a more holistic, hands-off approach. They maintain that by using sustainable methods over a long period of time, a vineyard will reach an equilibrium and produce a healthy amount of perfectly ripe, flavorful grapes year after year.

In 2018, California experienced a very large harvest of healthy grapes. The drought was over, and weather across the state was mild and stable during the crucial first part of the season. Cool temperatures toward the end of the growing season meant extra hang time for the grapes to develop additional flavor. I had a chance to check in with David Scheidt of Mastro Scheidt Cellars and Kenny Likitprakong of Hobo Wine Company. Both of them are known for spending a large amount of time in their vineyard sites and both of them had similar responses when I asked how the yield of the 2019 vintage is shaping up. So far, so good, although it doesn’t look to be quite as big as 2018 after flowering. Still, the season is young, and there is plenty of time for growers to take steps towards reaching their desired yield, all the while hoping Mother Nature cooperates as well.