Wine
The Timing and Chemistry of Harvest
November 1, 2024
Winemaking is an art that blends craftsmanship with intuition, and the nuanced decisions made throughout the process is what renders each steward so unique. Although fruit and fermentation remain the foundations of the craft, precision and discernment from the artist’s hands play a paramount role in the quality and longevity of what lives in the bottle—all of which trace back to the source, deep in the soils in which the vines flourish. In the closing days of the growing season, winemakers spend countless hours amongst the vines tasting grapes and assessing conditions, ensuring that grapes are plucked from the vine at the perfect moment—and when the pinnacle arrives, the work has only just begun.
Denoting an initial pick date is one of the most crucial decisions winemakers make year in and year out, as the consequences of working with imperfect fruit can be extreme. Although the 100-day-from-flowering rule has long been standard in determining a vineyard’s initial pick date, the dramatic effects of climate change—along with evolving tastes and technologies—have created a myriad of nuances around the decision. This is just one of the many reasons why choosing when to commence harvest remains just as much of an art as a science.
One of the first visual cues that ripening has begun can be found in the color of grape skins, specifically those that are red. As red grapes ripen, their green skins quickly take on a darker hue, a process of which is known as veraison. However, the simple turn of color does not signify that the fruit is ready to be picked.
Winemakers must also factor in the simultaneous ripening of the berries’ internal stems and seeds, which in grapes of all colors, turn from green to brown. This process takes longer than veraison, elongating the growing season past simply the moment when red fruit takes on its signature pigment.
Similarly, a tactility can be felt in ripe fruit. At peak ripeness, grapes are soft and smooth, as well as slightly soften under gentle pressure. Additionally, berries at peak ripeness will detach easily from their clusters, signifying that the ideal moment to harvest is close, if not imminent. When this harmony is achieved, and above all, confirmed sensorily by meticulous tasting and testing, picking is ready to commence; though the moment is fleeting, and doing so too soon (or too late) can result in imbalance in final wines—or a lot of tinkering in the cellar.
While taking science into consideration, the vast majority of wine professionals agree that the ultimate test of ripeness is taste, and skilled winemakers attune to its perfect state will immediately be able to taste the dynamic interplay of sweetness, acidity, and texture. Beyond the balance between sugar and acidity, the phenolic compounds found in grapes—which come from the skins, stems, and seeds—must also reach optimal ripeness, as these compounds provide the final wines with structure and depth. The key here is harmony: sweetness without bitterness, and enough acidity to balance the wine’s freshness. When picked too early, grapes will boast excessive levels of acidity, which can render the juice sharp and austere. On the contrary, when fruit is left too long on the vine, the opposite occurs; acidity quickly drops, rendering the juice flat and dense.
Another way in which nature signals the impending moment of harvest is through the biodiversity found within the vines. Birds, insects, and other creatures are drawn to grapes for their sweetness, and will often bear a stronger presence during moments closer to ripeness. While the presence of animals can be a helpful reminder that harvest is near, it can also cause a myriad of problems in terms of fruit loss. In response, various means of vineyard management to ensure that grapes remain on the vine are implemented, including shielding the plants with nets or adding predatory falcons to the vineyard.
In addition to pests, some winemakers have also taken to unique solutions to do their best to keep damaging weather at bay. One of these means is through the use of hail cannons. “Hail cannons are used to try to stop the formation of hail during a rain shower in a storm, explains Elyse Lovenworth, head sommelier at Sommsation. Lovenworth notes that when strong storm systems are in the forecast, hail cannons are deployed an hour to 30 minutes prior to the storm to attempt to shake off excess water accumulations so that they don’t freeze and become hail—which can ruin an entire vintage in one fell swoop.
The Influence of Weather
Although viticultural decisions surrounding pruning and soil management play a role in ripeness, its foundations are rooted in climate conditions. The sun’s warmth on the grapes is the strongest factor in ripening, and is greatly influenced by a vineyard's precise location and aspect. Southern-facing vineyards in the Northern Hemisphere will benefit from the most direct sunlight—especially when planted along staggering slopes—whereas the opposite rings true for vineyards south of the Equator.
Dramatic climate conditions have brought additional factors into winemakers’ picking decisions. Excessive rainfall, heatwaves, hail, and frost, can all influence picking time—or even destroy a harvest in the blink of an eye. Regions such as Burgundy and Willamette have been greatly affected by late-season frosts, which can halt a vine’s ability to produce fruit in a given year if experienced after budbreak. Similarly, prolonged periods of drought and wildfires, similar to those experienced by northern California in recent years, can also end a vintage in the blink of an eye.
Beyond the Surface
While a vineyard may appear a singular entity, each plant plays its own unique role in the symphony of its orchestra. Clonal differences from vine to vine, coupled with varied expositions and soil types, cause each cluster to advance at its own pace—meaning that one ripe cluster does not necessarily signify the perfect moment to pick. Beyond clones and conditions, factoring in the style of wine that said fruit is destined for will also play a role. Berries destined for sparkling wine, for example, will be picked less ripe than those used for fuller-bodied, still whites or reds, as more acidity is required for this type of vinification.
Though different clones and soil compositions may appear as a nuisance with regards to pick date, variety is the spice of life when it comes to a vineyard—and can actually ensure its well-being long term.
Using a selection of clones versus one singular clone aids against disease pressure, meaning that one negatively affected cluster doesn’t necessarily mean the loss of a whole crop. “Clonal melange, as it is sometimes referred to, helps create complexity in wine in the vineyard,” Lovenworth affirms, stating that each clone has distinctive characteristics that contribute to a wine’s final flavor profile, as well as dictates how it operates in a vineyard.
“For example, with Pinot Noir—where I think a lot of clone conversation happens, more so than other grape varieties—there are clones that are more aromatic, some bring more tannin structure,” she explains, additionally stating that some clones are early ripening, whereas others are late ripening, and that the amount of hang time on the vine impacts the phenolics of the grapes. “The most common clones of Pinot Noir, specifically those that we see in the Willamette Valley, are Dijon Clones and Pommard Clones, which are named after the cities in Burgundy from which they originated,” Lovenworth reveals.
Though clonal nuances go beyond the cities from which they are named after. “Dijon 113 is a moderate yielding, early-ripening clone that is very fruitful, where as Dijon 114 is a lower-yielding clone with floral notes, berry, cherry, and dark plum flavors,” says Lovenworth, additionally citing that Dijon 115 is the most widely planted clone due to its production consistency, while Dijon 777 is a clone that offers an ideal combination of finesse and power—and these are just four of the many Dijon clones that exist!
While the art of winemaking is steeped in tradition, chemistry and technological advances have also shaped the way in which vinification is done today. The modernization of machinery, measuring tools, and means of collecting information have provided winemakers with a myriad of ways in which to execute their craft—meaning that no two stewards, nor the wines produced at their hands, are the same. For wine collectors, there’s no more exciting time to enjoy the fruits of their labor than the present.
In the realm of, a wine’s acidity–measured in pH– must also be balanced with sugar levels (referred to as Brix in the wine world) to ensure harmony in the final glass. “The Brix measurement is one way winemakers determine the ripeness of the fruit which determines when they will pick,” explains Lovenworth. For example, grapes for sparkling wines are often picked at lower Brix levels (around 10 to 20 degrees Fahrenheit) so that enough sharpness and acidity remain intact to provide essential crispness. Still wines, on the other hand, tend to be harvested slightly later in the harvest season, where Brix levels between 19 and 25 degrees Fahrenheit allow for fuller, richer flavors. In optimizing the balance between sugar and acid, every variety at every vineyard has its own requirements for optimal harvest timing.
Though numbers and statistics only tell part of the story. Taste and expertise—which ultimately come with diligence and time spent in the cellar—coupled with personal preference and stylistic choices, are ultimately the deciding factors that guide most winemakers to craft the best wines possible, as well as create long-lived bottles that tell their vineyards’ stories best. For wine collectors, there’s no more exciting time to enjoy the fruits of their labor than the present.
Beyond harvest dates and picking, precision throughout the vinification process is just as essential. Brix are constantly rechecked, so as to guide winemakers in pre-fermentation decisions, as well as potential subsequent adjustments. “If there is no chance of grapes getting to the ideal Brix during a particularly cool vintage, and rain and cold temperatures are in the forecast, winemakers will be forced to pick the fruit and deal with the issue in the cellar,” Lovenworth elaborates, citing chaptalization as one solution, which involves adding sugar to unfermented grape juice to increase the alcohol content in the final wine.
On the other hand, if fruit is too ripe, Lovenworth notes that winemakers can add tartaric acid to help balance the wine, or implement reverse osmosis technology to physically remove alcohol from the wine after fermentation. “However, both of these options are considered to be highly manipulative and most winemakers keep these practices under wraps,” she reveals. Though in the realm of quality winemaking, these practices are almost never implemented.
In the end, winemaking reflects a choreography between nature, science, and craftsmanship. Because there is no determinative algorithm for success, the best winemakers complement their experience-based intuition with nuanced understanding of the chemistry involved to achieve transformative alchemy. Great winemakers, like great chefs, commune with their senses—taste, touch, sight–—while navigating the cognitive complexities of each harvest. Yet in both crafts, the goal remains the same: to elevate something simple into something sublime, and above all, to create a harmonious final product that reflects its unique time and place, and that confers on partakers the transitory ability to transcend everyday experience.
