I was at the theater a few nights ago. I was with some friends enjoying the stunning Yacobson Ballet of Saint Petersbourg’s “The Sleeping Beauty” and it got me thinking…. Don’t you see some kind of resemblance here? I mean… this beautiful girl—let’s imagine her name is Vine—sleeps for months until the charming Prince comes along—shall we call him Spring?—and wakes her with a warm kiss. Am I the only one who sees it? It’s the end of Winter Dormancy!
The period of dormancy in the lifecycle of a vine starts approximately in November (or May, if you live upside down) that’s when vines are trimmed and pruned. During dormancy, the vine does not rely on photosynthesis and must rely upon the carbohydrates--mostly starches--accumulated during the previous growing season in the roots, trunk and branches.
This is a very delicate moment in a vine’s life since extreme lows in temperature (Canada, New York State and China are perfect examples) can be harmful or even kill the vine when below −25°C (13°F). In some parts of the world, vines can be buried for protection against extreme cold.
Pruning is one of the most important activities in the vineyard during dormancy and it determines the way vines will be trained and grown in the next season. Winegrowers will put their best effort into this activity to ensure they reach their goals in terms of yield and quality at harvest.
So what happens when Prince Spring kisses the Beauty Vine? She starts to cry, literally! Is she emotional? Well, maybe a little bit… but that’s when life starts to stir in her once more. Wouldn’t you be happy too? Technically, this phenomenon is known as Acqua Vitis or Lachryma Vitis--when temperatures start rising and reach over 10°C (50°F) in the first days of spring, sap begins to flow again (basically water and minerals) from the roots through the vine’s veins, finding their way out from the open wounds of pruning.
In the past, winegrowers used to collect these ‘tears’ because they were supposed to have healing effects. Apparently, there are still a few farmers in Germany who do this and there are even face creams containing vine sap.
At this point, life has started flowing again and a whole lifecycle has begun. I always love to say that pruning is life and it couldn’t be more true. If the pruning staff does their job well (and you really hope they do) there will be buds on the canes of vines ready to burst. Once open and growing, they will then become our new shoots, leaves and bunches.
Not all grape varieties will burst open at the same time though. Some grapes are defined as “early budding”, meaning that they require relatively low temperatures at budbreak (a little less than 10°C). Some examples are Chardonnay, Pinot Noir, Merlot and Grenache. The grapes that need higher temperatures are referred to as “late budding” and include Sauvignon Blanc, Cabernet Sauvignon and Syrah. The advantage of a late budding grape is that the vine is less prone to spring frost, which is one of the biggest problems in the vineyards.
Carbohydrates stored in the roots, trunk and branches of the vine support the initial shoot growth, until the leaves begin to grow. As leaves develop and mature, they provide energy through photosynthesis. To be able to do so, they need adequate warmth and sunlight for this to take place. Most of the vine’s energy at this very moment is directed towards shoot growth until flowering starts. This will happen around June – July if you live in the northern hemisphere, or November – December if you live down under.
Broadly speaking, the fastest rate of growth occurs between budbreak and flowering.
The rate of shoot growth determines the vigor of the vine, which can vary between vines and even different parts of the same vine. This is also the moment when the long shoots are tucked within a trellis (if used) to ensure the canopy remains upright and to avoid shading.
Wanna know what’s happening next? Stay tuned and I’ll tell you next time what happens when prince Spring turns into Summer.