1.5.3.b What type of foliage structure is possible?

Is the varietal properly adapted to certain trellis types?

Certain varietals are vulnerable in the case of high winds and therefore more likely to break. The vines can either grow upright or cascade. This has an impact on the suitability of different trellising techniques.
For example, Grenache has a strong tendency to grow upright and is less likely to break. It is therefore, better suited to goblet pruning or a non-trellised structure. Merlot is a semi-upright growing varietal that can also be grown without a trellis system in certain zones.
On the contrary, Pinot Noir has a strong cascading tendency, it is therefore, better suited to a classic type of trellis system with a metal wire to best ensure the shoots will not break as well improve the microclimate. The use of stakes is also recommended.

What about a very warm climate?

In the instance of an extremely warm climate with a lot of sunshine, the risks are dryness or scalding. Some structures are therefore better suited to provide shade for the vines, such as goblet pruning or the Lyre system (sometimes referred to as the “U” system). This can be the case in California where the Lyre is used on certain plots.

What leaf surface area is required by each vine?

The height / spacing index (canopy height / space between rows) is a useful tool to help determine the optimum canopy height. It needs to be within a range of 0.6 and 0.8 meters. If the vines are spaced 1 meter by 1 meter, the canopy height should be 0.8 meters. Should the spacing be 1.5 meters, the canopy height should be increased to 1.2 meters.

With these values, we quickly see that a minimum trunk height is needed to prevent canopy overshading. It is possible to increase the leaf surface, but we increase the shading range and evapo-transpiration.

Finally, it is necessary to take into consideration equipment capacity. If we use a high-clearance tractor, it is important to respect each machine's limits and capabilities.

Once the ideal height is determined (H), we can determine planting density as well as the row spacing (E) and trunk height. Once all the variables are known, the total effective surface area of foliage (SECV) can be easily calculated. The necessary variable being leaf width (L).

SECV=(2xH+L)x(1-T)/E

In the case of a vine already in place, it is necessary to estimate the holes in the canopy (T). If the vines are new, we can assume that there are no holes in the foliage so T=0.
By putting the SECV in units of grape weight per hectare, we can see if our calculations were correct, as the number should fall between 1 and 2 depending on the situation. If not, certain modifications need to occur to increase the SFE (lyre pruning or “U” shape) or lower the yield objective.

R= SECVX10000 / Harvest Yield