A grape flower opens.1
The timing of flowering will tell us much about when to expect the harvest. Like all other pregnancies, ripening of the fruit is subject to a period of gestation and requires a certain number of days. How many days are required will be somewhat influenced by the yield (higher yield will require more time), the health of the vine, and the weather during ripening. Another key factor is the winemaker, and how ripe she or he would like the grapes. A rule of thumb is between 110 and 120 days, however ripening can occur in as few as 90 days and may require up to 140 days or so. It is about the weather, but it is also about yield, and about the health of the grapevine. For example, if flowering happens at the end of May, we can expect to harvest in mid-late September, but if flowering is delayed until the end of June, we may not finish picking until early November, because ripening weather of September-October will usually be somewhat cooler than August-September.
In the past few years, occasionally, one reads frightening stories, both in the popular press and in scientific journals, about how the Napa Valley wines have been—or will be—impacted by Global Warming. A group of us fellow winegrowers responded to these reports by saying, in effect, “Clearly Global Warming must affect our vineyards and we should do everything we can to study the situation.” We have worked to establish baseline conditions, and to assess what local climate change has occurred thus far. Moreover, we plan to attempt to predict what we can expect over the next few decades, and to entertain discussions in the Napa Valley about measures available to adapt to changes we anticipate. This subject merits an entire essay, which I will save for another time. One of the most valuable conclusions of our initial study is that, far more important than temperature data, are our records of the behavior (the phenology) of our grapevines. In other words, how have the vines responded to climate change? Each of the biological stages in the annual growing cycle of a grapevine gives us a natural signal of climate change. Moreover, when we consider climate change in the Napa Valley, is not how the vine grows and thus how the wine tastes, our primary concern?
It turns out that while the beginning of growth, Budbreak, can tell us a little bit, it is Bloom, the timing of flowering, that is a very useful and reliable indicator of how climate changes affect grapevine development. Based on limited data that reach back almost 60 years, we cannot yet discern a clear trend in Bloom. Growers in the Napa Valley began recording much more data in the 1990s, and, based upon the last twenty years, we have mixed results: certain varieties in certain districts show earlier bloom, while other districts appear to have later bloom. In other words, the signal of climate change in the Napa Valley may not be as strong as some reports might lead us to believe*.
That being said, it appears that, along with the timing of Bloom, the interval between Bloom and Veraison, when the berries turn purple and ripening begins, may also be a reliable indicator of climatic changes in the vineyard. Here in the Napa Valley, Cabernet Sauvignon usually needs about 70 days post Bloom to reach Veraison. Our data is variable and contradictory depending on the appellation. For example, we see the interval may be lengthening in St. Helena and Rutherford, while it may be getting shorter in Oakville and Spring Mountain. But in general, over the past two decades depending upon the region, the trend seems to be for the interval to shorten by somewhere in the range of one to four days, which would indicate a warming trend that we need to continue to watch. Check back in two decades and we’ll tell you what happened.
In our Napa Valley, the first varieties to bloom are Chardonnay and Pinot Noir, followed by Sauvignon Blanc and Merlot. Cabernet Sauvignon blooms later, perhaps two or three weeks after Chardonnay. Usually flowering begins in the warmest areas, mid-valley, and proceeds to the cooler locations, such as closer to the water (Carneros) or higher elevations (the mountain appellations). Spring Mountain is among the latest, and the vines in the Cain Vineyard, on the crest of the Mayacamas and exposed to the cooling breezes from the Pacific, are among the last to bloom.
What can we already say about the vintage 2012? In the valley, conditions at bloom were almost perfect. Since bloom occurred in our Benchland vineyards (along the edges of the valley floor) at the end of May, we hope to begin harvest in mid-September. Unlike the past four years, it seems that we will have a generous harvest, with uniform ripening. On the valley floor, look for 2012 to be comparable to 2005, or even 2007. In the Cain Vineyard, bloom is coming later, and is not yet complete, so it is too early to tell for sure, however it promises to be an easy harvest (the first since 2007), with much of our fruit ripening in the first half of October. Hopefully, the weather will hold out until Halloween. The one advantage that we have is a relatively small crop (about 1/3 of the valley floor)—and this year, the bloom is proceeding quickly, therefore we expect to have a very uniform ripening, so we will not need to thin as much.
But, as Yogi Berra said, “It ain’t over, ’til it’s over.”
My next writing will consider ripening, the process and how we think about it. Look for it this Fall—I’ll be working on it as we prepare for harvest.
—Chris Howell, Winemaker
*None of this discussion is intended, nor should it be used, to cast doubt upon the reality of global warming on the planetary level. Indeed, winegrowers in many regions have already experienced significant impacts. I hope to write more about the subject of Climate Change in the vineyard in another essay.
Text Copyright ©2012 Cain Vineyard & Winery, All Rights Reserved
All photos by Florence Dagueneau, 2008, Dom. Serge Dagueneau et Filles, Pouilly-sur-Loire, France
1 Image 6 (center top) Illustration,Tratado de Viticultura, Luis Hidalgo, 1993 Ediciones Munid-Prensa
Image 7 (top left) One must look closely to find the flowers hiding among the foliage.
Image 8 (upper right column) The cluster can hold more than a hundred tiny flowers. Illustration, Manuel De Viticulture, Alain Reynier, 5th edition, 1989, Technique et Documentation—Lavoisier, Paris
Image 9 (top left, second image down) A few weeks after bloom, the berries, still hard and green, are beginning to swell.