Farmers work year-round to ensure productivity and quality. Both Old World and modern practices rely on trellising systems—arranging vines on wires to maximize sun exposure—tailored to the needs of certain grape varieties and climatic situations. Here, farmers work to manage the microclimate—small areas within and between the vines.
A key focus of these activities involves controlling vigor—limiting the number of shoots and leaves—to prevent leaves from shading each other or the developing fruit that lies below the canopy of leaves. Smart and Robinson in Sunlight to Wine point out that if the entire plant—leaves and fruit—all receive ample sunshine, the plant will have enough energy to produce and ripen quality fruit.
To that end, farmers prune plants in winter to limit the number of shoots and then again in spring and summer to remove leaves that otherwise would produce shade—a process known as “leaf plucking.” Some farmers will also prune immature grape bunches, called “green harvesting,” to limit yield. In addition, farmers prune to facilitate a variety of trellising systems that open the canopy to sunshine and to control vigor. In areas with fertile soil and especially vigorous grape vines, trellising systems can be very complex. Where vigor is low, farmers use simpler systems and in some cases allow vines to grow in a “bush” format.
Vine density—the number of vines per acre—can also control vigor as plants compete for limited water and soil nutrients. However, dense planting can make vines difficult to prune, particularly in more fertile soils with ample rain.