Targeting a Harvest Date

• Posted on 17 September 2023
• Posted in California, france, Oregon, pinot noir, Virginia
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The vinedressers have made all the preparations. All the vineyard pruning, spraying, cultivating, and green harvesting have been accomplished. The air is cooling, and ripening has slowed. Perhaps a slight pause to consider the most magical day of the year: harvest day!

When is harvest? To get to the answer, let us assume that we have already decided upon a number of things to include, and there is a vineyard with the following influences: 

• Latitude drives the number of potential sunshine hours and, to a smaller degree, daily temperatures. Higher latitude, closer to the poles, generally experiences cooler climate, slowing the harvest date, where the fruit needs longer sunshine hours to ripen.
• Nearness to a body of water will drive potential amounts of rain. If by the ocean, the vineyard could experience a marine climate with a high amount of rain. The body of water, however, influences the daily temperature swings to mild or stable, between day and night. Here there is an even pace of ripening.
• Further inland, the vineyard could experience a continental climate, with a mild or almost nonexistent rainfall. The sun heats the valley floor, where the air rises during the day. As afternoon passes into evening the cool air slides down causing a much wider change of temperature than by the ocean. Here the accumulation of sugar has a stop-and-start effect, but the ripening of flavors can be a steady pace.
• Altitude to an extent drives temperature. The vineyard will experience warmth at lower levels which accelerates harvest. Or, the opposite, at higher altitudes the coolness slows harvest. Higher altitudes also drive a larger swing in daily temperatures, which helps keep acid in the grapes. 
• Physical height and angle of the slopes drive root access to water, heat, and sunshine hours. There is warmth on the slope, considering that morning cool air is heavy and slices down into the valley. The steeper slopes will receive the sunshine and warmth sooner than the valley, bringing fruit to fullness quicker.
• The steepness of the slope is also going to drive potential harvesting by machine (flat lands or gentle rolling hills) or having to harvest by hand (steeper hills and cliffs). The limiting factor for harvest by machine is when equipment is available if shared between vineyards, meaning harvest can be during the night when it is cooler. The limiting factor for hand harvesting is when staff gather together, during the daylight hours.   

Once the “where in the world is this vineyard” question is answered, there are a few other questions to address. What kind of wine is going to be produced, red, white, rosé, sparkling, amber? And what grape(s) is (are) going to be planted, given the above decisions already made?  More specifically, the question is what varietal can achieve balance at harvest considering acid, sugar, flavors, aroma, color, and tannins in the vineyard, given the above choices already made?  The winemaker and the vinedresser communicate during the season for a shared vision of the end product of a vineyard, given the weather and other factors. The actual harvest date, determined by the vinedresser, is driven by three velocities—how quickly the sugar is accumulating, how quickly the acid is dropping, and how quickly the flavors, aromas, color, and tannins are developing. There are other factors, but for this purpose, let us consider these three elements.

Taking these factors to a practical application, consider the characteristics of Pinot Noir, specifically. It is an early-budding, early-ripening grape. It has thin skin that can be easily bruised, become rotten, and spoiled. It is a cold or cool climate grape, meaning that the climate helps to slow down sugar development, so that the fruit can have time to develop flavors and tannin. It is often produced around the world as a red wine, but in some places, will also be produced as a sparkling, rosé, and even a white wine.

Pinot Noir is one of the main varieties grown in Champagne, France. Considering the three velocities, keeping high acid is most important. Then, having enough sugar to potentially achieve 11.5 to 12.5 percent ABV is next important. Developing color, flavors, and tannins is least important. Here is how this plays out for when to harvest. Champagne is at a high latitude for growing wine grapes, it is a cold, fairly rainy region, meaning despite having the opportunity of more sun hours (higher latitudes), the rain clouds prohibit sunshine, slowing down flavor and tannin development and keeping acid high. Malic acid is metabolized (consumption of acids) in respiration (process of the plant using up the sugar made through photosynthesis and turning it into energy) during the ripening stage. Respiration is slower at cool temperatures than warm ones, which is why cooler climates tend to produce wines with higher acidity.

Sugar is eaten by yeast, which creates byproducts, of which alcohol is one. Plants produce sugar as a result of photosynthesis, which is very rapid at the start of ripening and slows down. The daily temperature drives the rate of this accumulation, meaning that the cooler temperatures in Champagne will produce sugar slower and to a lower level at harvest than other world regions. Extreme temperatures, hot or cold, can stop accumulation. As the fruit is nearing the end of ripening, the vinedresser uses a portable refractometer to measure the sugar content, or Brix level, which helps to determine the potential ABV level the grapes can achieve—not necessarily “will” achieve as the winemaker can stop fermentation early, allowing the wine to have some level of sweetness. 

Last, let us consider the velocity of color, flavors, aromas, and tannins when growing Pinot Noir in Champagne. The bigger flavors in Champagne are created in the winery with the specific production method that is “Méthode Champenoise,” which is a different blog. Even still, wine is made in the vineyard well before any production steps are imposed. There is a point in ripening called “version,” where the fruit transforms from small, green, hard berries into red, supple, soft berries. The berries increase in size with the addition of water and sugar. The acidy starts to drop. The tannins, created by the skin, seeds, and stems, become less astringent. Anthocyanins, colored, water-soluble pigments, develop. And phenolic, flavors, chemical compounds ripen that affect taste, feel and color found in the pulp, skin, seeds, and stems of grapes. So, what is important to know here considering when to harvest? Got the high acid, got the sugar level in spec, next is to consider the astringency level of tannins. If the seeds, skin, and stems are unripe, meaning high astringency and tannic, this will affect the wine’s ability to produce the fine bubble in the second fermentation. Also needed to help control tannins is a labor staff large enough to hand pick the fruit to reduce bruising and oxidation of the juice. Meaning that if the juice is allowed to sit with the ripped skin and unripe seed, it gains tannins, which decreases the quality of the juice intended for Champagne.

When is harvest in Champagne? Ultimately there is a public administrative institution with legal personality under the Ministry of agriculture, food, and forestry, the National Institute of Origin and Quality (Institut national de l'origine et de la qualité [INAO]), together with the Comité Champagne, that reviews data points from all over Champagne. They determine the maximum yields authorized to pick, and when picking can start.

The above of course just covered sparkling wines. The question of when to pick fruit for rosé, white, and red are also influenced by the same points adjusted for the style aiming to be produced. For white wine, like the Champagne, harvest is influenced by retaining high acidity, sugar to produce a stable wine of 10-12 percent ABV, low color, and high aromas. For rosé wines, color is a little more important. For red wines color, tannins, aromas, and flavors become a lot more important. But by that time, vineyard activity would have to adjust for acid dropping and sugar developing, so that the harvest date will still produce a balanced wine. Not that a vineyard that produces pinot noir intended for white wine will not be the same vineyard that is intended for red for these reasons. Harvest then would be in the order of grapes intended to produce white first, then rosé, then red.