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- Friday, 06 September 2013 09:42 | Written by Stefano Chioccioli
The vine is a generous plant. For centuries, it has given man an unique drink: rich, complex, different from zone to zone, with diverse character and personality.
If the goal is to produce a great wine, especially a big red wine, understanding the natural production of the vine is essential to the quality that we want to achieve.
The average fertility of the Vitis vinifera vine is 1.5 bunches per bud, which means, for example, that for every six buds left after the winter pruning, I'll get an average of nine bunches per vine. The average weight of the bunch of the vine depends on the different varieties cultivated and generally ranges from 80 to 100 grams, such as with Cabernet Sauvignon, although it can go up to 200 to 250 grams with certain varieties and, in particular, indigenous varieties.
You can imagine then that on average, six buds left after the winter pruning of a Cabernet vine will yield about 900 grams of grapes, while other varieties, such as Sangiovese, Montepulciano of Abruzzo, Refosco, Nero D'Avola, and others, will yield from 1.8 kg to more than 2 kg of grapes per plant.
The plant’s production must always be compared to the leaf surface resulting from the pruning of the vine in winter and spring, which usually produces about 2 square meters of leaves in all the varieties bred to "espalier,” such as horizontal cordon or guyot.
The oenological goal of growing the quality of grape able to produce a great red wine for ageing that is rich and complex in aroma, without aggressive, dry, and bitter polyphenols, is to produce a maximum of about 1 kg of grapes for every 2 square meters of leaf surface.
With these considerations, we understand that for some varieties it is very easy to get great red wines because they were born naturally more balanced in grape production. This also explains why these varieties have spread with greater speed and facility in the world (international varieties).
For other, less well-known varieties with a strong personality and identity, as the native ones, you will require a more specific and detailed technical knowledge to counter-balance this natural generosity in order to produce rich, complex, and polymerized polyphenols that define a great red wine.
This is when the “green harvest” or thinning of the bunches comes into play. The green harvest reduces the production of the vine up to 50% of its initial production and also distances the clusters from one another to create an ideal microclimate to ventilate the area around the clusters. The green harvest should be carried out in the phase between the beginning and the end of veraison (the change of color in the berries).
This operation must be carried out with extreme care by skilled and motivated staff so as to avoid irreparable errors.
Typically, we cut the more distal, the higher, and the more compact and closed clusters. Ultimately, all of those clusters that have less chance to get to the perfect ripening of the grape's polyphenols are sacrificed, harvesting them in advance and throwing them to the ground.
With this important and very innovative agricultural technique, we have been able to discover unexpected quality even in varieties considered minor until a few years ago. These varieties were minor because they were too generous, but with the intervention of the technical culture of man – green harvesting – varieties such as Aglianico, Sangiovese, Nero D'Avola, Negroamaro, Perricone, and Frappato have proven to have in their DNA all the potential to produce great wines with strong personality, identity, and terroir.