In the final part of our series on harvest, Westgarth Wines' own wine specialist Maurizio Broggi looks at environmental and practical constraints that might impact the timing of the harvest.

Grape composition is ideally the primary factor that should drive the timing of harvest; however, things do not always go as planned (and in fact, in the vineyard they rarely do). Environmental and practical constraints, notably weather, vineyard site characteristics, and logistics, may significantly impact the picking decision and seriously affect the winemaker’s stylistic goal.

Severe weather conditions during the final stages of ripening can make or break a vintage. Cooler, more humid regions such as Burgundy or Bordeaux face the threat of rain or hailstorms at harvest time which may lead to rot and damaged grapes, ultimately causing loss of crop and negatively affecting grape quality. Intense rain close to harvest may swell grape berries and dilute fruit. Some varieties, such as Cabernet Sauvignon, have thicker skin and are more resistant to rot, thus rain is a risk that may be taken if the weather conditions after rain are favorable (i.e. warm, dry, and windy). In warm to hot regions such as Barossa or Napa Valley, warm, dry conditions may result in grapes ripening too quickly, leading to a rapid decrease in acidity, thus compromising the overall balance in the grape composition. Likewise, heat spikes close to harvest may result in the dehydration of grapes causing the development of dried and baked fruit flavors. Therefore, it is crucial for the grower and winemaker to monitor the weather in order to anticipate and react promptly to adverse conditions.

The decision to harvest may be further complicated by factors that are related specifically to the vineyard site. Variations in topography, soil, vine age, and even vine diseases may affect how the grapes ripen and may therefore impact the timing of picking. Some plots of vineyards may be harvested at the same time, while others may require several days of monitoring until the grapes have achieved optimal ripeness.

The logistics of harvest are complex, requiring meticulous planning and coordination, and have a strong impact on the picking decisions. Once grapes are harvested, the winery must have enough capacity and tank space to process the fruit and manage the fermentation. All the resources necessary to process the fruit, such as labor, transportation, equipment, tank capacity, and facilities, must be forecasted in advance to ensure a smooth process and avoid bottlenecks. Planning and coordination are crucial. Any delay may result in grapes remaining on the vines (over)ripening or sitting in harvest bins waiting to be processed, affecting grape composition and thus style and quality.

Fruit harvest scheduling is critical. Sometimes, the picking process may be slower than expected or the winery is unable to process fruit fast enough due to a lack of equipment or fermentation vessels, or simply the crop is larger than expected. In warm to hot climate regions, producers may opt to harvest only at night or in the early morning when conditions are cooler. This reduces the amount of grapes that can be processed per day. In such situations, the winemaker must prioritize fruit based on what is the most at risk or the most critical.

A wine’s potential quality is strongly dependent on the quality of the grapes harvested. While achieving optimal ripeness is the starting point to making high-quality wines, setting the harvest time is one of the winemaker’s trickiest and most delicate decisions, profoundly affecting the success of a vintage.

The most essential factors that impact the timing of harvest will depend on the wine style, the vintage conditions, and the winemaker’s intentions. There are no systems or devices developed (yet) to accurately identify the ideal date of harvest. The numerous dynamics at work and parameters to assess make selecting the time of picking more an art than a science. Ultimately, the winemaker’s experience is key in deciding which are the critical factors that must be prioritized to achieve the stylistic and qualitative goal set for the vintage.

Want to read more? Take a look at some of our other blogs:

• • The art of timing the harvest
  • How winemakers measure grape ripeness
  • The basics of biodynamic winemaking