During the recent Masters of Food & Wine event in Carmel, California, Matthew Lane of Australia’s illustrious Penfold’s winery was asked about his philosophy regarding the treatment of grapes at harvest. Lane leaned into his microphone, and twisting a cork between his fingers said, "It doesn’t matter what treatment we apply to the grapes in order for them to ferment and age appropriately. The quality of the fruit has already been established in the vineyard. There is nothing more we can add to what nature has already done."

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The winemaking process undoubtedly begins in the vineyard. From the first buds of spring through the harvest, everything that happens within the microclimate of a vineyard affects any wine that can be produced from grapes that are derived from those vines. In early spring, however, it is difficult to predict a remarkable or faulted vintage. There is no swollen canopy. There are no heavy clusters of grapes that suggest a bountiful harvest. There are only the stubby, pruned trunks and the winemaker’s hope that the weather conspires to satisfy a near perfect vintage. Unfortunately, there is no proven equation for a perfect vintage. It is a combination of luck and opportunity – a lucky growing season that produces high quality grapes, and the opportunity to produce a healthy wine from that fruit.

In the vineyard, we depend on a long, warm, dry summer – far and above the best of circumstances for the development of high quality grapes that show a mild amount of acidity and bold sweetness. Too cool of a year will produce unripe grapes with biting acidity and very little sweetness. Similarly, a rainy year might produce dilute plump grapes with little character. In other words, everything that happens in and around a vineyard – weather, fire, rain, hail – is revealed in the grapes made by each vine.

There are other circumstances that contribute to the quality of any given vineyard – terroir, orientation to sunlight, sound vineyard practices among them – but none plays so large a role as weather in how a vine reveals the essence of the growing season in the grapes it produces. Through the winemaking process less-than-superior grapes stand a chance of becoming at least a good wine. But bad grapes will never make an incredible wine.

Several characteristics are paramount in deciding when to pick, or how to “crush” the grapes and initiate the fermentation process. At harvest, we choose which grapes to pick (and when) based on the ripening process of each vine. Some vines ripen early. Others ripen later. Rarely is an entire vineyard perfect for picking at the exact same time.

Over the course of the growing season a vine’s grapes will decrease in acidity. At the same time, the sweetness of each grape increases. Depending on the varietal, harvesting grapes at a pH of between 3.2 and 3.7, and between 23 and 30 brix (sugar level) is best for most still wines that will be fermented dry. Standard deviations in this practice occur for wines that are fermented to differing levels of sweetness. For instance, a Sauvignon Blanc destined to be a dessert wine would be harvested months after grapes intended for a dry table wine.

No matter what varietal we are working with, there are few (if any) exceptions to the rule that a warm dry summer is the single-most important aspect in the production of laudable wines. Ultimately, winemaking is an artisanal science – the creative arrest and manipulation of a vine’s natural reproductive process – but it is a science that in no small way depends on the weather.

One cycle of a vineyard year might follow a schedule similar to this:
• January, prune vines to encourage growth in the spring;
• February, prepare vine cuttings for potential planting to expand or fill in gaps in the vineyard the following spring;
• March, aerate the soil as buds begin to form;
• April, pray there are no frosty nights that might inhibit shoot growth;
• May, continue praying there are no frosty nights that might stunt vine growth and spray to prevent mildew;
• June, the shoots begin to flower;
• July, spray against mildew and till the soil to kill weeds;
• August, veraison (in dark colored grapes marked by the change from green to black) marks the beginning of the ripening schedule;
• September, maintain a secure perimeter around every cluster of grapes (so birds and animals do not eat them) as they begin the final ripening period and begin the harvest;
• October, continue harvesting;
• November, if in a cold climate, protect vines for the winter by covering bases with soil – if in a warm climate, relax;
• December, survey the vineyard for repairs and maintenance prior to pruning.