Vine training

The use of vine training systems in viticulture is aimed primarily to assist in canopy management with finding the balance in enough foliage to facilitate photosynthesis without excessive shading that could impede grape ripening or promote grape diseases. Additional benefits of utilizing particular training systems could be to control potential yields and to facilitate mechanization of certain vineyard tasks such as pruning, irrigation, applying pesticide or fertilizing sprays as well as harvesting the grapes. In deciding on what type of vine training system to use, growers will also consider the climate conditions of the vineyard where the amount of sunlight, humidity and wind could have a large impact on the exact benefits the training system offers. For instance, while having a large spread out canopy (such as what the Geneva Double Curtain offers) can promote a favorable leaf to fruit ratio for photosynthesis, it offers very little wind protection. In places such as the Châteauneuf-du-Pape, strong prevailing winds such as le mistral can take the fruit right off the vine so a more condensed, protective vine training system is desirable for vineyards there.

While closely related, the terms trellising, pruning and vine training are often used interchangeably even though they refer to different things. Technically speaking, the trellis refers to the actual stakes, posts, wires or other structures that the grapevine is attached to. Some vines are allowed to grow free standing without any attachment to a trellising structure. Part of the confusion between trellising and vine training systems stems from the fact that vine training systems will often take on the name of the particular type of trellising involved. Pruning refers to the cutting and shaping of the cordon or "arms" of the grapevine in winter which will determine the number of buds that are allowed to become grape clusters. In some wine regions, such as France, the exact number of buds is outlined by Appellation d'origine contrôlée (AOC) regulations. During the summer growing season, pruning can involve removing young plant shoots or excess bunches of grapes with green harvesting. Vine training systems utilize the practice of trellising and pruning in order to dictate and control a grape vine's canopy which will influence not only the potential yield of that year's crop but also the quality of the grapes due to the access of air and sunlight needed for the grapes to ripen fully and for preventing various grape diseases.

...
Wikipedia