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A grape flower opens.
A grape flower opens.1

Surprisingly, most wine lovers have no idea how or where the grape cluster forms on a vine. And even many extremely knowledgeable wine connoisseurs know very little about flowering. Still more surprising, many New World winemakers, who buy their grapes (or “source” their fruit, as they like to say), may not even be aware when their vines are flowering.

Of all the moments in the annual growing cycle of the grapevine, flowering is least noticed and yet the most defining.

To the casual observer, flowering happens privately, almost in secret, with no apparent signal. The vines have been growing for several weeks. The shoots are now a couple of feet long and finally are growing rapidly; each day they might add another inch or two. The foliage appears to fill the trellis. The flower clusters are hidden under the leaves—that is, unless one looks carefully.

For many weeks, these nascent clusters are quite unremarkable. Each flower is just a tiny unopened bud—at first, vanishingly small, as small as a poppy seed, about the size of this asterisk: * Just before bloom, the individual flower will have grown to the size of a fat sesame seed, about the size of this zero: 0.

Because they are so tiny, it is easy to understand why so little attention is paid to these flowers, and yet flowering is the critical moment in the entire cycle. The moment of flowering is the single most controlling factor of the timing of harvest (early or late) and thus the odds of achieving full ripeness. Moreover, the conditions of flowering are the primary factor controlling the quantity and uniformity of the harvest.

Imagine a perfect day in early summer. The morning is refreshing but not cold, and the afternoon warms up nicely under sunny skies, but it is not hot. A gentle breeze caresses the skin. Walking in the vineyard, amid the most delicate, ethereal perfume, so delicate that at first, you don’t notice, but then it pings your consciousness. Attention aroused, you take a peek amid the foliage and there you see the tiny flowers open, five minute stamen surrounding each pistil. With a hundred or more flowers, the cluster appears gauzy, enveloped in a delicate fur. It is a happy moment.

That is the ideal scenario. Naturally, things don’t always work out this way. First, the individual flowers on a cluster do not all open simultaneously. And then, certain clusters may be somewhat in advance of others on the same vine. Between vines, the differences can be even greater. If the temperatures are unseasonably cool, the flowering can begin slowly, and the last flowers may not open for a couple of weeks after the beginning of bloom. A protracted bloom will inevitably lead to less uniform ripening.

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The grape flower can pollinate itself. The grape flower can pollinate itself.2

No bees are required to produce grapes. If a flower becomes successfully pollinated, the odds are that it pollinated itself. The flowers of Vitis vinifera are hermaphroditic and they are normally self-pollinating. Once pollinated, an ovary will begin to form a seed. The flesh at the base of the flower, surrounding the seed begins to swell into a tiny berry. Each flower holds four ovaries and thus can form up to four seeds—the more seeds, the larger the berry will grow.

Even under the best of conditions, not all of the flowers will be successfully pollinated. Many will abort; they will dry up and fall off. And not all the berries will contain four seeds. A good average is when about half of the flowers eventually form berries. Especially, up at Cain, the berries may hold just two seeds. The berries will be smaller, and the wine more intense. Grapevines can be temperamental, certain varieties, certain selections, especially so. If it is too hot and the vines have too much water, they will be growing rapidly and the energy that should have gone to the flowers goes instead to the growing shoot. The flowers, forgotten by the vine, simply fall off. On the other hand, if the weather is cool, the vine is producing less energy, and again the flowers are simply not as fertile. In the worst case, the result can be almost no crop at all. This happened in one of our blocks of Malbec in 2011.

At first, the berries don’t look much different than the flower buds that came before—except that now there are many fewer, so the cluster appears scanty or even ragged. After a couple of weeks, the clusters become recognizable, although the berries are hard and green, and still not much larger than a pea. Over the course of the summer, the berries continue to grow, and the definitive grape cluster begins to form.

A sense of mystery surrounds flowering. Many growers leave the vines alone during this sensitive moment. They will not train the shoots or spray the leaves; they will not cultivate the soil. Is it superstition, intuition, or common sense? Even when Science has explained so much, the essential mystery of life remains. As in the case of Biodynamics, some winegrowers have revived an awareness and attention to the astrological calendar of their distant ancestors.

Who can blame them? It is clear that industrial agriculture and the science of agronomy do not provide all the answers.

Besides the intrinsic fascination, there is also a very immediate and practical reason to attend to the flowering. As we observe the process unfold, we will learn what to expect at harvest time, and when to expect it. There may be many berries or very few. The berries may have all formed at nearly the same time, or their formation may be widely separated in time, and each berry may be at a slightly different stage. The clusters may be full and compact, or they may be loose and ragged. All of these factors will inform our choices later in the summer, when we thin the crop.

Read on for Part Two of Two
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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 1 (center top) A grape flower opens. Illustration, A Wine-Grower’s Guide, Philip M. Wagner, © 1945, 1965, Alfred A. Knopf, New York City

Image 2 (top left) In the Springtime, the new cluster is barely apparent.

Image 3 (upper right column) As the vine grows, so too does each flower bud.

Image 4 (top left, second image down A happy moment on a sunny day: all the flowers are in bloom at once.

2 Image 5 (center bottom) The grape flower can pollinate itself. Illustration, Viticoltura Moderna Manuale Pratico, Giovanni Dalmasso; Italo Eynard, 8th edition, 1979, Ulrico Hoepli Editore, Milano

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Cain Vineyard & Winery | July 2012

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