When most of us think of the life cycle of a grapevine, images of lush, green leafy canopies and ripening grape bunches leap to mind. While the period from bud break to harvest is the most obvious display of how the fruit of the vine turns into wine, there's much more to it. During winter, a series of essential changes take place in vines. These changes lay down the groundwork for new growth in spring and play a role in determining the success of a new vintage. So just what happens in the vineyard during winter? Let's take a look.
Not So Dormant
After the harvest, temperatures dip and winter begins to settle in. Vines transition into a new phase of their life cycle. Their brightly colored autumn leaves fade from vibrant yellows, oranges, and reds to brown and fall to the earth. Once the grape bunches are picked and the leaves fall, only the trunks and canes of a vine remain. While the barren vines may have you believing that winter is a sort of shut down period, this isn't actually the case. It's true, vines go into dormancy during the cold months, temporarily ceasing all above ground growth, but beneath the surface, things are not so quiet. Instead of directing their energy towards producing fruit or new leaf growth, in winter vines expend their energy into their root systems. Roots will grow, soaking up soil nutrients to keep the vine strong during winter, while simultaneously preparing for spring and the emergence of new shoots.
During the growing season, vines store carbohydrates in the trunk. Stored carbohydrates play a pivotal role come spring. This reserve, combined with the nutrients the roots absorbed from the soil, will give vines the energy they need to grow new leaves and shoots once winter has passed and the ambient temperature reaches to 50 degrees F or above.
Caring for Vines in Winter
Just because the harvest is over doesn't mean there isn't work to be done in the vineyard. Winter is an equally important time for farmers as they use winter dormancy to prepare for the next growing season. Winter pruning is one of the most crucial aspects of vine management. Canes from the previous year are cut back and new canes are chosen from which shoots will grow come springtime bud break. It's a delicate process. This critical step dictates how many buds will emerge come spring and ultimately, how many leaves and grape bunches the vine will produce. And as some of you may know, like aspects of terroir such as climate and soil, the grape yield can be a determining factor in grape quality.
For high vigor varieties, pruning can make all the difference in the quality of the grapes. Under pruning can lead to too large a canopy or too many bunches, thereby reducing quality. But over pruning is also a problem. In this case, vines will spend much of their energy growing leaves rather than producing and ripening fruit. Not an ideal result for the winemaker. Winter pruning also allows winemakers to remove any potentially infected areas of a vine which may arise during a wet post-harvest season.
In regions where there's a risk of frost or snowfall, it is also essential for winemakers to protect their vines from harsh weather. One way this is accomplished is by covering the base of vines with earth or straw. This puts a stop to erosion brought on by storms and helps keep some of the worst effects of the cold at bay. In especially chilly regions, some winemakers may choose to use strategically placed heaters throughout their vineyard to fend off potential damage by severe frosts.
So the next time you take in the sight of immaculate vineyards blanketed under a heavy snowfall, remember that while things may look quiet on the surface, there's a whole lot of work being done below ground. Though they may appear to be asleep, vines are hard at work making ready for a new growing cycle which with any luck, will give rise to a fantastic vintage.
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