Soft pruning of the vine

Technical articles - Climate resilience, Diseases

Viticulture Pruning and training of the vine

Faced with the decline of French vineyards caused notably by wood diseases, some winegrowers are modifying their practices of pruning in favor of techniques that increase the vitality of the vine plants. Practicing pruning that respects the physiology of the vine has a significant impact on diseases of the wood, improves uniformity, plant health, and the quality of the grape.

This method applies to all types of pruning : single, mixed and double guyots, cordons, goblets, lyres...

Physiology of the vine

To implement gentle pruning of the vine, it is essential to understand its physiology :

A vine stock develops by stacking concentric layers of wood every year. The shoot of the year, which generates the plant's energy, is connected to the annual diameter growth of the wood.

Leaves, through evapotranspiration, generate a suction tension in the wood vessels, causing the circulation of raw sap (water and mineral salts) from the roots to the foliage. Once transformed into nourishing sugars via the photosynthesis of the leaves, this elaborated sap loaded with nutrients descends back down the plant through the bark.

In midsummer, tensions exceeding 15 bars can be recorded in the wood. The plant is therefore a hydraulic system. Like any system transporting water under pressure, tightness is essential.
The current year's shoot is watertight and continuously connected to the vessels it has built in the wood. These newly created vessels allow the annual circulation of raw sap. At times of strong sap flow, vessels from the previous 2 or 3 years are used to circulate enough raw sap for the plant's functioning.

A pruning practice that ignores this concentric functioning leads to pathologies related to sap circulation.

Principles of gentle pruning of the vine

Gentle pruning of the vine implements the following principles :

Group wounds on the same side of the stock to limit complications in sap circulation.
Accept and control a minimum elongation of a strong bud (inevitable on a woody plant).
Adapt the trellising to the plant and not the other way around (trellising must evolve to accompany the progressive elongation of the plants). A generalized reduction of arms in the vineyard causes a sudden drop in yields and is followed by a wave of apoplexies a few years later. Raising or removing a trellis wire is less costly and less traumatic for the plant.
On short prunings (cordons and goblets), accept a minimum elongation of a bud opposite to the previous year's cut or prune only on one-year-old wood by systematically choosing the second shoot on the spurs of the previous year (preferably on very fruitful varieties).
No longer shave pruning wounds and allow their coverage.
Avoid large pruning wounds and regular reductions.
Group and manage successive pruning wounds.
Keep as much living cambium as possible by preserving "sap pullers".
Adapt the grape load to the vigor potential.
Maximize the use of photosynthetic and prophylactic space.
Build trellises serving the plants.
Implement virtuous green works!

How to make good pruning wounds

Do not obstruct sap flows.
Facilitate the coverage of pruning wounds.
A correct pruning wound is defined by a respected collar and ridge of the bearing axis and rapid coverage.
A length reduction of a shoot must be managed as follows :
- On the next diaphragm = ideal pruning.
- Middle of two diaphragms = correct pruning.

Gentle Guyot pruning

On the Guyot, it is necessary to anticipate the elongation of the vine arms by leaving a significant margin below the tying wire.

This facilitates bending operations and the shoots emerging on the canes are more regular. The distribution of shoots on the wire is also improved.

Create continuous sap flows to feed the fruiting wood

By grouping pruning wounds on the top of the stock, sap circulation is freed from any obstacle or pinching responsible for many apoplexies.

A continuous sap flow guarantees good nourishment of the fruit-bearing wood.

The plant, formed by successive years of growth, gradually covers pruning wounds and increases its reserve potential.

The positive impact is very significant in terms of health and quality.

Create a continuous sap flow while limiting arm elongation

Always prioritize the choice of spur according to the arm elongation axis.
Preserve sap flow (no wounds on the underside of the arm) and control elongation. Fluidifying sap circulation prevents shoots from emerging in unwanted places.

To create this sap flow, there are several scenarios :

Choice of the first strong bud below the spur (ideal)
No first strong bud below the spur (elongation accepted) so bud thinning of the first bud. This technique complies with the rule "never put the spur after the cane".
No first strong bud below the spur (elongation accepted) so inversion of the one-year cane without consequences for the plant allowing easier cane healing.
First strong bud : on top of the spur leave a bud to allow the sucker to emerge (to be avoided as elongation is less than the size of the wound).

Adapt the load to the vigor of the stock

Pruning does not control the vigor of the stock. Indeed, it only allows adapting the load to the vigor. Vigor, in turn, is mainly controlled by the soil.

Depending on plant vigor, various methods are possible :

Normal vigor : load for the following year of 9 to 10 buds
Excessive vigor : increase the load to 14 buds
Low vigor : decrease the load to 4 buds. By reducing the load, similar grapes are obtained. To increase the vigor of this stock, it is also possible to remove all clusters to keep 100% of the energy in the plant. From year N+2, when the reserve volume is greater, the plant will resume proper growth.

When all shoots are the same size, it means the load is adapted to the plant's vigor.

When canes are hollow in the middle (wood present at the base, almost nothing in the middle, and large wood at the end), it means there is too much load.

Guyot Poussard pruning

The idea of this pruning is to make a spur on one side and a cane on the other with enough to make a spur on the sap flow.

This pruning is often difficult to optimize with trellising :

The wire height is often far too high
It is necessary to evolve the trellising to allow easy bending and favorable bud direction
A large number of severe prunings are linked to this inappropriate wire height

Gentle pruning on cordons and goblets

Respecting a pruning direction or orientation allows :

Better distribution of fruiting
Controlled and homogeneous elongation across the plot
Reduction of sap circulation problems
More effective wound coverage
Easier pruning

Summary

Advantages

Increase in quality of production.
Increase in quantity of production.
Decrease in mortality of stocks.
Fight against vineyard decline.

Limitations

Necessity to train well.
Time / investment / benefit balance to be carefully evaluated : gentle pruning takes more time than mechanized pruning but better preserves the health of the vines.