As we enter the month of August, it becomes a time of great excitement and anxiety in equal measure for grape growers across the northern hemisphere. For months, producers have been carefully tending to their vines in the hope of being rewarded with a healthy grape crop, sufficient to make delicious wines. So what does harvest entail? And what are vignerons actually looking for?

Let us first take a step back to the beginning of the year, when old wood from the previous vintage is pruned and cut back. This annual “haircut” ensures new growth can emerge, keeping vines energised as well as reducing risk of disease. When temperatures start to rise in spring, new buds will surface from the freshly cut spurs, with shoots producing both leaves and inflorescence. Over the following weeks, the vines’ flowers will self-pollinate, producing tiny, hard green berries which continue to grow and ripen until the end of the season. This period is known as veraison and is arguably one of the most beautiful times of the vineyard cycle, with grapes turning from green to yellow to gold or green to pink to purple.

Most vignerons will know when to pick grapes from experience or simply tasting the fruit, but there are many other ways to gauge the ultimate harvest date. On a basic level, grapes are made up of sugar and acidity, with sweetness increasing and acidity decreasing over the warm summer months. The level of sugar in the grapes will dictate how much alcohol can be produced in the finished wine, whilst the level of acidity will define how much freshness there is on the palate. As harvest approaches, grape growers will select bunches from different vineyard sites, press a little juice, and run an analysis on these sugar and acidity levels, as well as pH, to evaluate the optimum time to pick. Furthermore, some wine regions have the harvest dates dictated to them in order to protect the growers crop and the appellation’s reputation.

Depending on the grape variety, climate and size of the vineyard, harvest dates and processes can vary immensely. For example, in Champagne, grapes are harvested sometimes as early as the middle of August in order to retain freshness in the final wine, key to the sparkling style. Conversely, grapes in Alsace can be picked as late as December owing to the dry, long autumns, creating grapes that are rich with sugars and complex flavours. White grape varieties do not need much time for their skins to ripen, whereas red or black grape varieties will require a longer period of ripeneing to ensure tannins and phenolics don’t taste bitter. Sometimes, it’s simply the weather that commands the harvest date. If a producer has to choose between an extra day of ripening and losing their entire crop to a thunder storm, it’s likely the grapes will be brought in to the winery a day early to save the vintage!

In fact, when producers talk about a good or a bad vintage, they’re really talking about the weather, and what difficulties they had to overcome during the growing season. The most common problems include spring frosts (when newly emerged, vulnerable buds can die due to below freezing temperatures), hail, rain, heat and drought. It is overcoming all of these challenges and unexpected obstacles throughout the year that makes a successful harvest so special. And so we wait with anticipation to see what our favourite wine growers make of this vintage, and hope that 2020 merits the fruits of their labour.