As the climate crisis deepens, the question arises: should growers prioritize extending ripening periods or pushing forward the timing for harvesting?
Gradual ripening is typically linked not only to “cool-climate” viticulture but also to an overall enhancement of the wine’s quality. With climate change causing warming trends, it would seem straightforward that, to adapt, there should be an encouragement for grape varieties that ripen more slowly, including specific clones or selections.
This is certainly the perspective of Jon Bonné. His detailed, thought-provoking, and insightful book, The New French Wine, advocates for a focus on “later-ripening” varieties or selections due to their supposed advantages in an era of climate warming. The intriguing aspect, however, is that this viewpoint seems contradictory in a narrative that consistently supports biodynamic farming. When engaging with many biodynamic practitioners, it becomes clear that they often emphasize the benefits of early harvesting, citing features like liveliness and lower eventual alcohol content, which they argue are made possible precisely because biodynamic methods encourage flavor development before sugar levels rise. Moreover, the promotion of strategies designed to enhance ripe flavors while limiting potential alcohol levels—such as postponing or forgoing hedging—is not exclusive to those who practice biodynamics.
Should the approaches to viticulture and vine selection be aimed at achieving extended ripening periods? Or should the focus shift toward techniques that allow for earlier harvests? Curiously enough, these divergent methods stem from a shared aim of enhancing flavor—by maintaining acidity for brightness and moderating alcohol levels while not compromising on the unique deliciousness of the wine. This creates a common framework for assessing their effectiveness. However, we must consider the possibility that choosing either method could lead to a compromise in quality.
The option of an earlier harvest—assuming the grapes are deemed ripe-tasting—raises questions due to at least two key factors. The first is irrefutable: picking earlier increases the chances of doing so in warm or hot summer weather, which poses difficulties in maintaining aromatic freshness and acidity. Nonetheless, utilizing nighttime harvesting or chilling chambers (which are becoming more common) along with the ability to quickly harvest can significantly mitigate these challenges, particularly for those who can invest in the necessary manpower and equipment. Insect pests also pose a significant risk, although typically only a hard frost would eliminate them, and such a fortunate occurrence before harvest is becoming increasingly uncommon.
Referring to chilling as a luxury brings up a more fascinating, yet complex, issue. It’s widely accepted that the variation in temperatures throughout the day and cooler evenings not only helps preserve the acidity of the grapes but also positively affects their aromatic qualities. This idea is often encountered in regions that are considered “cool-climate,” such as parts of Lower Austria or Germany’s Rhine basin. While it might be less frequently mentioned by producers in Champagne, this could be to avoid drawing attention to how often recent harvests have commenced as early as the first days of September. Unfortunately, scientific literature on this topic is rather limited. However, research by Fulvio Mattivi at the University of Trento has shown a negative correlation between temperature and levels of rotundone, lending credence to the claims made by Lower Austrian winemakers that cooler conditions enhance the characteristic pepperiness of their Grüner Veltliner. While we could include various supportive remarks from prestigious wine growers about the benefits of chill on phenolic enhancement, we can also consider the perspective offered by Klaus Peter Keller from Rheinhessen—a standout among them—who emphasizes that “cool nights produce the finest Rieslings,” noting that “when autumn temperatures drop to zero [°C], it seems that the aromas intensify, creating a different density and complexity in the grapes.” He concludes by stating, “Often, there isn’t time for slow processes, and grapes must be harvested at their peak ripeness, regardless of whether the weather is cold, cool, or warm.”
Understanding the relationship between acid retention and cooler temperatures is complex. During cool nights, malic acid is preserved, but it diminishes due to daytime metabolic activities, whereas tartaric acid content in grapes tends to rise. However, during extremely hot conditions, vines can halt their processes, effectively preventing the breakdown of malic acid just as cooler nights would. Tartaric acid plays a significantly larger role in shaping the perception of a wine’s vibrancy and refreshing quality. Additionally, malic acid often converts to lactic acid unless this transition is restrained by high pH levels, extremely cold storage conditions, or some form of intervention, even if it’s simply through earlier bottling.
Furthermore, the impact of a prolonged ripening period and time spent on the vine brings advantages that go beyond the benefits of differing temperature variations. Mimi Casteel, a prominent Oregon winemaker and advocate for regenerative viticulture, emphasizes in a podcast interview with Jesse Frost on November 4, 2022, “You just can’t replace [time] with anything else. You can maintain vibrant green foliage with nitrogen, but when the growing season concludes, it’s simply over. You can clearly see when the plants and fruit are ready. If our growing seasons are going to become shorter, hotter, and drier, we need to focus on creating the infrastructure that will allow for prolonged time on the vine, during which the vines can continue to support metabolic activities.”
The inquiry of “sooner or later?” may not have a clear resolution. Some growers might focus on delaying the onset of flavor ripeness, while others may strive to hasten it; both groups might claim success through shared sensory evaluations. Undoubtedly—at least for now—remarkable wines are being produced by both approaches.