Harvest decisions and the complexity thereof

by Cain Hickey, Viticulture Extension Educator, The Pennsylvania State University

Harvest is an exciting part of the season. It is the culmination of the long growing season. The harvested crop is taken into “safer” realms in tanks, bins, and barrels to eventually produce wines that will be enjoyed. Harvest is also a stressful time of the season. Schedules change several times and logistics need adjusted accordingly. The reward from the last five or six months of hard work (not counting dormant pruning) is at stake. And, among other variables that will be further discussed below, the outcome of harvest is dependent on weather patterns which are out of our control. Such is the life of farming and, in our case, growing grapes. But it is worth it. And, grape growing challenges are not unique to Pennsylvania and humid growing regions in the US; grape growing and harvest challenges abound in growing regions worldwide, from the western US to New Zealand, to European countries, and regions in between.

Cabernet franc ready to be harvested.

Harvest decisions are the result of knowledge that is applied to the unique combination of cultivars and growing conditions of each vintage.

“Harvest” is a timely topic in Pennsylvania. From now through the end of October, grapes will be harvested and processed into wine throughout the Commonwealth. Some grapes may even be harvested into November and beyond in regions where ice wine or “late harvest” production is a goal. After Dr. Molly Kelly and Dr. Gill Giese presented their “A Balanced Harvest” webinar (https://bit.ly/32ohHPR), I was inspired to try and document several considerations that go into harvest decisions. And not necessarily doing so by citing literature. But, rather, by summarizing and reflecting on what I have learned from being involved in viticulture research, education, and extension and working with members of the eastern US wine industry over the past decade. I will paraphrase previous experiences and conversations with growers. And try to make points through the use of fictional case studies to exemplify circumstances that may be encountered in commercial vineyards.

Do we have an extensive enough literature base to cite how the combination of site, cultivar, management decisions, post-veraison weather patterns, and primary and secondary metabolites manifest in the resultant wine? We do have pieces of this story. For example, in humid growing regions, we generally understand that exposed grapes have potential to have less rot, lower acidity, and greater aroma and color development relative to shaded fruit. However, it would be a lofty goal to write a review on all the factors that can affect wine quality potential and thus dictate harvest decisions. Conclusions from such a review would be highly speculative in order to account for the multitude of variables that influence harvest decisions. Further, it would be difficult to apply any conclusions across the unique terroirs in grape growing regions, even just in the “humid growing regions of the US” which encompasses southeastern, midwestern, mid-Atlantic, and northeastern US states. Harvest decisions can be nebulous and are difficult to research and draw conclusions from unless “harvest date” is a factor in the experimental design. There are scenarios that limit the ability to make an objective statement about harvest decisions. Take, for example the recent and highly divergent weather patterns throughout the post-veraison periods of 2018 and 2019. All other variables standardized, these vintages will likely result in different wines.

To further make a case that harvest and related decisions are difficult subjects for objective statements, let’s consider whether the vineyard or cellar is more impactful for determining harvest. Is harvest a viticulture-based or enology-based decision? The answer: “yes” (as in, “both”… but with a weak attempt at humor). As a viticulturist, I am biased. I could argue the harvest of grapes is only possible because of the vineyard and its judicious management in the current and previous seasons. Which is true. However, I know that Molly Kelly, Penn State Enology Extension Educator, would justifiably argue that we harvest grapes with winemaking goals in mind. Which is also true. And I know that, in commercial situations, harvest date is often a mutual decision between the vineyard manager and winemaker; sometimes one person occupies both roles and, in other situations, the vineyard manager and winemaker work together to decide the optimal harvest date. I am not sure if the decision is easier to make as an individual or as a collaborative decision… this opens up psychological debate which goes far beyond my expertise. I’d ask enologists and winemakers to be forgiving of the text written herein, as it may be biased toward the vineyard and I may show ignorance about many important enological considerations for harvest decisions.

Destemmed Cabernet franc.

Harvest decisions are a consequence of several factors, some predictable and many not, that are unique to each commercial situation.

Harvest decisions are a consequence of experiencetheoretical knowledgeseasonal vineyard management practices, and numerical and sensory-based measurements that are put into action under the constraints of site, cultivar, post-veraison weather patterns, labor availability, stylistic winemaking goalsvineyard acreage and winery tank space, and current inventory of wines. Read that previous sentence again; it is a lot. And, while thorough, it still falls short of exhausting the number of potential factors that may impact harvest decisions. So, what can we predict for sure about harvest decisions and timing in Pennsylvania? With rare exception (site limitation, vintage effect, wine stylistic goal), Chardonnay will be harvested before Petit Verdot. And, most grapes will be harvested between late August and late October. These are the limited number of “predictable outcomes”. “Unpredictable outcomes” may become more predictable with an increase in breadth of knowledge and experience, especially with the same cultivars grown on the same site. I wish there were more objective statements that could be made about ideal harvest decisions and parameters. But, “ideal” is dependent on several factors, including those words/phrases that are emboldened/italicized above. To read more about how each emboldened and italicized word/phrase from the first sentence of this paragraph may impact harvest decisions, see this file (I kept this text separate so as to reduce the length of this blog post):

Chardonnay ready to be harvested (photo courtesy of Rachael White).

Practical vs. abstract approaches to harvest.

Note that the use of the terms “practical” and “abstract” is not meant to impose partiality to one approach or the other, nor to suggest that approaches to harvest only exist in these two forms or only in contrasting extremes. But rather to highlight how harvest decisions can be vastly different and dependent on values and goals. The practical-minded grower may error on the “safe side” by picking early to get rot-free fruit in the winery that also may have a lower pH and is likely to be microbially stable; the “risk” here may be picking fruit at less than optimal maturity for a targeted wine style. In contrast, the abstract-minded grower may error on the “riskier side” by picking based on sensory observations to make wine with fruit at peak maturity; the “risk” in this case may be that fruit rot and pH have increased as a consequence of “extended hang time”. Can one be practical and achieve optimal fruit maturity? Absolutely; theory and practice can come together in the real world. And, “optimal fruit maturity” is highly subjective and dependent on winemaking style goals. However, the combination of variables mentioned above (site, cultivar, post-veraison weather patterns) will affect the chances of theory and practice coming together in the form of rot-free fruit that has balanced chemistry and flavors such that little amelioration of the must is necessary before fermentation commences. The more odds that are against us (lack of experience, poor vineyard management, poor cultivar match with site, adverse weather patterns, labor scarcity, etc.), the more difficult it will be to achieve targeted wine styles, regardless if one is more abstract- or practical-minded. Most stakeholders likely have a balance of practical and abstract approaches to harvest in an attempt to achieve fiscal sustainability (e.g. by avoiding extreme bunch rot and crop loss) and to produce wines with recognition that round out the offerings of various wine styles in the tasting room. Winemaking “intervention” is necessary when harvested fruit is over-ripe, under-ripe, or falls short of the ability to achieve the intended wine style.

Destemmed Petit Manseng.

Take home.

Harvest decisions are complex and sometimes difficult. And justifiably so – lots is at stake. You want the best possible outcome (balanced, pleasant wines) from the crop you have worked hard to cultivate and maintain free from diseases and other pests all season long. Aim for the greatest quality each vintage. The successful approach to achieving quality starts during the dormant and growing season by practicing good viticulture. Use every advantage you have to make judicious harvest decisions. Be able to predict your harvest schedule but allow for some flexibility and be prepared to change plans as circumstances change. There are constraints in every vintage. As the number of adverse situations (rainfall, bunch rot, poorly drained site, suboptimal vineyard management) increase, there is greater need to take a pragmatic approach to harvest. Be practical in dealing with constraints to make the best harvest decisions possible; this requires the use of past experiences, knowledge of viticulture and enology theory, and an understanding of how current season viticulture management, weather patterns, and numerical and sensory observations will impact crop quality and the ability to achieve your targeted wine style. Acknowledge limitations of your cultivars grown on your site and be prepared to be responsive to the weather patterns of the immediate past and future.

The Winemakers Research Exchange, funded by The Virginia Wine Board, has published a newsletter with several Harvest Reminders. You can access this newsletter by clicking here: http://www.winemakersresearchexchange.com/august-2020-harvest-reminders-1

Chambourcin ready for processing (photo courtesy of Rachael White).

Hopes for a great 2020 vintage.

My sincere best wishes to all for a wonderful 2020 harvest! May the weather be dry with just enough intermittent rainfall to keep canopies photosynthetically active yet limit downy mildew and rot development.

All the best to each of you!

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