The purpose of pruning vineyards is to remove the old tendrils which have already yielded fruit, making space for potential new ones. The pruning method can be specific to the grapevine’s age and size, and in some cases it can be intensive, carried out by large pruning machines. The goal of pruning is to monitor and control the following year’s yield. A low amount of pruning will result in a large amount of fruit, which is generally of low and varied quality. Excessive pruning may prevent the grape berries from developing a satisfying amount of sugar in the ripening period (leafage deficiency). In our winery, we make sure to maintain a crop load of 800-1,200kg per 1/4 acre.
Thinning Tendrils and Shading
Controlling the grapevine’s growth is a combination of correct pruning and the arranging the leaves on the tendrils. Arranging the tendrils on the grapevine is important from two aspects: exposing the leaves to the sun and exposing the fruit to light and air. It is important that all the leafage is exposed to the sun, and not shaded, in order for the photosynthesis and sugar creation process to take full effect. However, it is important for the fruit to be exposed to both air and light, but not directly, in order to prevent sun damage, particularly the singeing of leaves. On the contrary, too much shading and “burying” the fruit among the leaves will cause a lack of ripeness in regard to color creation.
Monitoring Fruit Ripening
The fruits’ ripening period is most critical for the winemaker, particularly in regard to intense exposure of the grapevine to pests and disease, and also in regard to determining the right timing for harvesting. From the moment of veraison, when the grape berry starts to change color, there is an accumulation of fruit components, among them phenolic compounds – colors, tannins and aroma compounds– and other components such as sugars, carboxyl acids, minerals, amino and proteins. The winemaker has to assess the correct harvesting time, in regard to accumulation of sugars and acid. If harvested too early, the sugar level may be too low to create alcohol, whilst a harvest conducted too late will result in a drop in acid level and harsh pH corrections. Each grape variety has a desirable sugar level which influences decisions in choosing a harvesting date. In our winery, the first to reach a desirable level of ripeness, and thus harvested first, is the Merlot, and the last to be harvested is the Petit Verdot. The Barbera is an especially problematic variety to grow, and we do not receive the desired aromas, sugar and color every year, which is why there are years in which we do not harvest the Barbera whatsoever.