Late vine size
Faced with climate disruptions and significant episodes of frost in spring, some winegrowers implement a pruning late in the season to increase the resilience of the plots. Late pruning of the vine encompasses techniques based on a deliberate delay in carrying out traditional interventions. This allows to delay an overly accelerated and/or unbalanced ripening of the grapes.
This article presents three of these techniques.
Postponement of the pruning period
Postponing winter pruning can slow down the ripening speed of the grapes. In this case, pruning is delayed by 1 to 3 months after the usual intervention date. Late pruning allows the vine to evolve simultaneously in its vegetative and productive cycle. The results of this technique are more evident in short pruning systems than in long pruning systems.
Postponing pruning allows to:
- Significantly reduce the sugar concentration in wine
- Decrease the degradation of organic acids and optimal must pH values, without negative influence on anthocyanin and phenolic content.
This technique seems optimal for short pruning agricultural systems. In this case, pruning postponement consists of a mechanized pre-pruning carried out in mid-winter at a height of 8-10 buds followed by a spring finishing to select and shorten shoots. Due to the resource limitation induced by late pruning, the development of inflorescence beginnings already induced during the previous summer may partially lose their capacity to produce functional flowers. Consequently, considering the slowdown of technological ripening obtained, this technique could be used in situations where it is necessary to contain productivity and slow down grape ripening.
No intervention after véraison
A second technique consists of not intervening after véraison to avoid competing with cluster development during ripening.
This technique allows:
- A significant reduction of sugars in the must, without modification of pH and content of organic acids, anthocyanins, and tannins
- A postponement of the harvest
Induction of photosynthetic stress
It is also possible to implement a technique based on the induction of controlled photosynthetic stress. From véraison, the most important leaves for grape ripening are those located in the middle and apical part of the shoot. Thus, if the objective is to slow down grape ripening, a late mechanical defoliation, post-véraison, focused on the upper part of the canopy can be considered.
Removing about 1/3 of the leaf area allows a reduction of sugars in the grape must by at least one degree Brix, without penalizing other composition parameters of both grapes and wines.
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