June is an exciting time for vintners. All of the promise of this year’s vintage already exists within the new shoots of every vine. Seeing their vibrant color, I’m always reminded of Dylan Thomas’s words, “The force that through the green fuse drives the flower/Drives my green age …”
Walking through the vines, I can imagine the plants furiously making new cells. From day to day, it’s not hard to see the changes as the shoots push up toward the sun, but it’s the invisible life of the vine that will determine the outcome at harvest.
Every bud on every vine contains three hidden nodes, each one with the potential to make a new shoot. All of the buds for this year’s crop were made last year; the fruitfulness will already be determined by how much sunlight those buds saw last June. Two of the nodes within each bud may be fruitful, but the third, smallest node is there only in case the others are damaged, and won’t produce clusters.
After the long, cold winter of 2015, many were concerned that fruiting buds or new canes might have frozen. It was alarming, back in April, to read a flurry of blogs and bulletins from grape specialists in other regions, with dire warnings of damage, and what to do if any was found. Lake Erie was especially cold, with temperatures that bottomed out in February at -21°F. Washington State’s extension experts offered detailed instructions for inspecting buds with a razor to predict the level of damage, with recommendations to leave multiple suckers on vines that would need to be revived from the ground. In the Finger Lakes, specialist Tim Martinson advocated pruning vines to short spurs instead of long canes to further protect them.
Fortunately, here on Long Island, it never gets as cold as it does in more continental regions. Our proximity to the ocean protects us from the worst freezes. As our own grape specialist Alice Wise noted, “Even when we had single-digit temperatures, it was in the coldest part of winter and thus the vines were fully dormant. We fortunately avoided wild swings in temperatures that can sometimes predispose vines to winter injury.”
Full dormancy in winter also delays spring bud break, offering greater protection from spring frosts. Here, shoots emerge at the beginning of May, but in many West Coast vineyards, bud break in March leaves soft shoots susceptible to frost for several weeks. The California drought impacts growers who depend on irrigation sprinklers for frost protection. On the other hand, vines not tempered by cold may set so much fruit that yields are higher than the vines can properly ripen.
We all know that the soils and climate of a vineyard—its terroir—profoundly affect the characteristics of wines from every region. Whether the soils are clay, stone or sand, or the sun shines directly or obliquely on the vines, all determine how the plants will prosper. Those aspects are easy enough to see and measure, but there is an unseen world that also determines terroir. This is the biome, or the microscopic life of the vine.
Gilles Martin of Sparkling Pointe in Southold has participated in an international merlot biome study that was recently published in M-Bio, the journal of the American Society for Microbiology, titled “The Soil Microbiome Influences Grapevine-Associated Microbiota.” The statistical analysis is truly mind-blowing, with input from 12 researchers in New York, Illinois, North Carolina, Massachusetts, California, Spain and China. They identified bacteria in leaves, flowers, grapes, roots and soils of merlot from Long Island, Bordeaux and California over the course of two growing seasons to try to pinpoint biodiversity in terroir.
No simple task, right? We think of bacteria as evil pathogens, but plant bacteria can also be positive. For example, steroidobacter, found more in roots than in soil, “control seed germination, stem and root elongation, vascular differentiation, fruit ripening, leaf expansion, and stress protection in plants,” according to the study.
Yes, grapevines are on steroids.
This intensive study showed that specific bacteria are indeed highly localized in grapevines, influenced most by variations in pH and the ratio of carbon to nitrogen. Although bacteria from below ground differed greatly, 80 percent of the grape samples from Long Island and Bordeaux, and most samples from California, had similar bacteria, suggesting there is a core of grape microbes that is “independent of growing region, climate, and sample collection method.”
That leaves the definition of terrior, still, to the poets.
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