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2.1.1.a Pruning Fundamentals

Pruning allows a vine's length to be controlled over time, as well as its vigour and grape production. The grape variety and region will define how the vine is structured when pruned.

There are numerous examples, such as the Médocaine pruning method in the Médoc, simple Guyot in Burgundy, or Gobelet in the Rhône valley. Pruning gives the vine its shape, and if carried out successfully, it ensures the vine’s longevity and therefore the sustainability of production. The following year's work will depend largely on how this critical task is executed.

Cordon pruning at Eisele Vineyard

Load impact on vineyard management

When pruning, the number of buds left on the vine is called the load. The quantity of buds will directly determine that year's yield.
Pruning that leaves too high a load will lead to excess vegetation and grapes, which will require corrective interventions throughout the growing season. Conversely, pruning that leaves too low a load can lead to a vine imbalance, causing the production of lots of excess shoots that would then need removing.

Moreover, depending on the grape variety, bud fertility varies depending on their position on the shoot. Cabernet Sauvignon, for example, is generally less fertile at the vine’s base, so long Guyot pruning is preferable.
However, care must be taken not to leave excessively long shoots, as this can result in acrotonic growth. This means that the buds at the vine's base do not develop, leading to elongation and weakening of the vine.

Impact of the pruning date on the vine's growth cycle

The pruning period begins when the leaves have fallen and ends at budburst. Waiting for the leaves to fall is necessary so that the sap has time to fully descend. Pruning dates will alter the onset of budburst. The later the pruning, the later the budburst, or bud break.

Merlot budburst at Château Latour

For example, Château Latour has conducted a study over several years on several Merlot plots.
The study's results showed that budburst occurs differently when the same plot is pruned early in the season (end of November), compared to when it is pruned at the end of the pruning season (early March): budburst can be up to ten days later if pruned late. Delaying pruning can help avoid late frosts and delay the physiological cycle, so that some stages, especially flowering, take place in milder weather (even if this is not always true). The gap between the various phenological stages then narrows as the growth season progresses until the harvest when it is more or less non existent.
In reality, late pruning for all plots is logistically very difficult because there are not enough qualified personnel available over such a short period of time.

Impact of pruning techniques on the vine's lifespan

Pruning is by its nature a source of injury for the vine. Each wound creates a dry area known as a desiccation cone which leads to a reduction in sap flow. Various fungi can then cause necrosis on these cones, some of which are responsible for wood diseases such as Esca.

It is possible to leave a cone that protrudes one and a half times the shoot’s diameter to prevent the wood near the buds from drying out. This cone can be cut shorter later when the wood is dead.

Desiccation cone left during pruning
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