You’ve heard of the grape harvest. But when does it actually take place, and how? And what does it mean for the winery? The third in our series of educational Millesima Tips will explore the harvest, perhaps the most exciting aspect of winemaking.
What is the harvest?
A key stage of the annually recurring vine cycle and the moment in which the patience of the winemaker is most lavishly rewarded is the harvest: the picking of grapes from the vine at the time when they have reached optimal maturity.
The Harvest Season
Harvest can take place at different times, depending on where in the world the grapes are grown. In the northern hemisphere it generally takes between the months of July and October, while in the southern hemisphere they occur between February and April. The date of harvest is determined by the winemaker and the decision is based on the point at which the grapes have reached the desired level of ripeness. For most still wines, this means very ripe grapes with a balanced sugar-acid ratio (close to 1).
Well before the fruit is picked, many appellations announce and make official the beginning of harvest season. This is one of the most exciting times to be in a wine-producing region, as the beginning of the season is often celebrated with a festival or party. In certain regions, these celebrations date back for centuries and have become an important part of local culture.
Setting the Date
Even within a single hemisphere, the date set for grape harvest can vary vastly, depending on the climate associated with a wine region. Grapes located farther north may take longer to ripen, resulting in a later picking date. Vineyards located more to the south, on the other hand, enjoy a higher degree of exposure to the sun and the grapes are picked earlier, since they mature earlier on in the summer. So while wine harvest in the Mosel region of Germany may occur at the end of October or even fall into late November, wineries in Sicily might harvest months before.
The date also depends on the variety of grape being collected. As a general rule of thumb, white varieties tend to be picked before red ones. And while Pinot Noir is often picked early (around September in the average northern hemisphere wine region), varieties like Cabernet Sauvignon are collected later on in the season. Often winemakers prefer to cultivate grape varieties that require picking at different times. In the Piedmont region of Italy, for example, the Dolcetto variety tends to ripen before Barbera, which is generally followed by the harvest of Nebbiolo, around 2 weeks later. This allows wineries to divide their time and resources, increasing their yield and variety.
Along with the variety of grape, the type of wine for which those grapes will be used also determines the harvest date. Grapes used to produce dry white wines, for example, are picked earlier in order to avoid the rapid decrease of malic acid composition. By picking the grapes earlier, they retain this acidity, leading to greater freshness and liveliness in the glass. Sweet dessert wines, on the other hand, are produced from grapes collected late in the season, when the acidity has been reduced and sugar concentration is higher. Often dessert wines even include “late harvest” on the label, as in the Alsace region of France.
It is important also to not pick the grapes too late, since the concentration of the grapes’ phenolic compounds decrease over time. These compounds are responsible for the colour and tannin level of the wines, which greatly affect the mouthfeel and texture of the finished product.
Green Harvesting: A New Trend in Winemaking
After the mid-90’s green harvesting became the newest winemaking trend. This is a style of crop thinning, the practice of cutting unripe (green) clusters of grapes from the vine in order to more closely manage the yield of each plant. This practice forces the plant to spend more of its natural resources to ripen the remaining fruit. Green harvesting is typically carried out around veraison, the period during which the grapes change colour from green to yellow or red.
While green harvesting has become popular, it is often met with criticism from agronomic engineers. This technique has its limits, and too many clusters can be an important indication of bad vine performance – notably overly vigorous vines and an imperfect winter size. Ridding the vine of its green clusters also changes the natural behaviour of the plant, often resulting in larger grapes, more diluted in flavour. Green harvesting can result in a larger yield in the following year but the grapes are often characterised by a reduced organoleptic quality.
How to obtain high quality grapes?
The world of wine has witnessed several technological developments over time, in the vineyard, the vat room and, especially, in the reception area of the cellar, where the grape clusters arrive fresh from harvest. The machines used to facilitate the process – sorting tables, thermo-regulated stainless steel tanks, cold fermentation – are constantly being improved. One aspect, however, has remained the most important throughout thousands of years of winemaking history: the climate.
Heavy precipitation before or during harvest can lead to the dilution of polyphenols and aromatic compounds in the berries, leading to lower quality wine. Hot and dry weather, on the other hand, can block maturity by triggering fermentation at the worst possible time, before or during the vatting of the grapes. In these cases, it is imperative that the grapes be transported quickly in order to avoid degradation or oxidation. The containers used to transport or store the grapes must be of a consistent and limited size. If they are too large, the grapes can end up crushing each other, damaging their sensitive skins. Small crates are used during harvest to avoid this.
While the final outcome of a wine – its colour, bouquet of aromas, its flavours and mouthfeel – depends on a wide range of factors presenting themselves throughout the vine cycle and vinification process, the outcome of the harvest is perhaps the most critical. A poorly timed harvest or imperfect climatic conditions during/right before it can lead to a lower quality in all wines of a certain vintage (year of the harvest). Good weather and an expertly timed harvest calendar, on the other hand, can result in a great vintage, which is talked about for decades after.Discover another article on the harvest (techniques and the effect of global warming) here