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A Unique and Complete Guide to Pruning Grapevines

Grapes are one of the sweetest and subtlest tasting fruits. In addition to having great health benefits, replete with vitamins, minerals and other nutrients, grapes can be a delicacy indeed, but also delicate to grow. What is more delightful than eating grapes, is growing them. Grapevines can be immensely gratifying, and vineyards can be greatly profitable, monetarily, and spiritually. Once a vineyard has been established its ongoing management is necessary to keep it in top producing form. This process starts at pruning and matching the vine, as this sets the vine and the system up for producing fruit in the following year. There are many other management interventions that are used during the growing season, and other methods that fine-tune the grape product. The productivity and quality of the produce is crucially dependent on the undertaking of these practices.

Pruning and Training

Pruning and training of the vine are two of the most important aspects for good quality of grape production, whether it is for consumption, table, wine production or other uses. How the vine is pruned and trained affects and interacts with where the vine is growing, the proposed end product and style of management. The two practices are firmly linked intertwined. Essentially, through pruning and training, the vine is shaped, altered, modified and manipulated to fit within the volume of the trellis that has been made available for it.

There are two main types of pruning that can occur:

Summer pruning

The purpose of summer pruning, that is, removal of green shoot parts during the growing season, is mainly to get the canopy to open up, preventing self-shading, or just merely to tidy up the external appearance of the vines. 

Winter pruning

The main purpose is preservation. The real and concerted effort and work in pruning happens during the dormant season, winter, when a decision has to be made as to the quantity, how much, and the choice, which parts, of the previous season’s growth, need to be removed.

Aims of Pruning

● To establish and maintain the vine in the desired form.

● To produce the grape fruit of the target composition.

● To select the nodes that will produce fruitful shoots.

● To regulate the shoot number or the crop load.

● To regulate the vegetative growth.

A key concept in thinking about pruning is maintaining a balance. In the case of most grape growers, the balance lies in preparing the vines in order to produce an economically viable crop, but also so that not too much time and energy is spent in ripening that crop at the expense of their ability to grow in the subsequent and following seasons. This is a consideration in the cropping of any perennial plant. The carbohydrate balance of the vine and its relation to management is also vital to consider. As the pruner leaves a greater number of nodes on a vine, they leave not just more growing points or shoots, but also potential fruit, considering all the clusters on those shoots. Thus, pruning has a significant influence on the ability of a vine to grow and to produce a crop.

Looking at this in further detail, if you approach a vine in the dormant season, you will see canes that were the shoots from the previous season. On each of those canes, there are a number of nodes. At each of those nodes present, is a compound bud that may contain three preformed shoots. Each one of these shoots is capable of growing, and each may, or may not, have flower cluster primordia on them, which may lead to further fruiting. In most of the cases, only the some of the largest of those preformed shoots will actually grow in the spring. So, if a vine was not properly pruned, it would simply seem like a very large bush, with shoots emerging and coming out at all angles and from almost everywhere on the old vine, each potentially and possibly carrying fruit.

Now, if pruning is carried out for that vine back to just a few nodes, in the spring, there will be a much more limited number of shoots emerging or coming out, as well as  a much more limited and manageable amount of crop. Ideally, this would result in the exact same number of shoots as many as the number of nodes left, with each shoot having some potential crop on it. In this case, there will have been pruning off of a lot of the potential vegetative and reproductive growth of the vine. In the spring, it will possess and have  a much smaller leaf area available, with which to photosynthesize and produce and make carbohydrates and, perhaps more pertinently and importantly, it will be having a very limited and concise fruit load. The result of this will be rampant growth of those particular shoots, the pushing and expelling of many latent buds that were left over from previously removed canes or shoots, and also the growth of other verdant preformed shoots in the compound bud.

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Types of pruning

The principal methods of pruning happen to be as follow-

Cane pruning

The fruiting shoots for the next season come from a length of the previous season’s shoot, which is laid down and wrapped on the fruiting wire of the trellising system. The goal is to choose canes that are-

(i) in a good and favoourable location to retain and maintain the shape of the vine;

(ii) well-exposed in the previous season, so as to give maximum fruitfulness;

(iii) have a good periderm formation;

(iv) not be excessively thick or thin.

The latter two criteria or parameters are associated with the cane’s ability to withstand cold while being dormant and increased fruitfulness in the following growing season.

The advantages of cane pruning are that vine fruitfulness is maximized and the number of potential non-count nodes on the vine is minimized, because there is less permanent wood on the vine and therefore less surface area from which latent buds can arise. As some cultivars are inherently less fruitful at the basal node positions on the shoot, cane pruning reduces its relative impact.

Spur pruning

Also called cordon pruning, Spur pruning does away with continued use of canes by establishing a permanent arm, or cordon, from a cane. In establishing a cordon, shoots arising or growing from the downward-facing bud on the original cane are carefully removed, leaving every alternate and upper node positions present. Downward-pointing shoots do not grow so profusely or vigorously, and, if shoots from both nodes were to be used, it would quite enlarge the fruiting zone, making some of the management practices more difficult. To counteract the loss of shoots from some of these positions, the canes arising from the remaining nodes are cut back to typically two-node spurs. When training a cane that is decided or destined to become a cordon, it should not be so wrapped as tightly as if the vine is cane pruned every single year. Too many of the revolutions around the wire can result in girdling of the cordon as it increases in girth.

Advantages of spur pruning are that it is much easier to teach and train unskilled people on techniques and practices of how to do it, and it is also possible to partly mechanise and revolutionise the process using technology and tools like cutting bars, which means that the crew that goes in afterwards has much less brush-pulling to do. Spur pruning also results in the vine having more permanent vine material, which has been implicated in fruit quality.

No matter what the pruning system, there remain some tips to smooth the pruning process. If movable foliage wires are used in the trellising system, be sure to move these down before budburst as then they will catch the shoots as they are raised. If any trellis posts or wires have broken, your only chance to fix them is at pruning, before any tying down of canes has to take place.

Growing the best grapevines is often a comprehensive result of the best management practices. A well-planned and informed effort results in a better yield any day.

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