Pruning Grapevines
Pruning grapevines is necessary to allow them to yield the most amounts of fruit. Grapes are only produced on 1 year old growths, not on 2 year olds or older. If you do not prune them these older branches grow too much and more energy is used by the plant for this growth. This leaves less energy for fruit growth and ripening. It is best to have a good pruning plan for your grapevines to get the most fruit yield. In order to prune your grapevines, you will need some pruning shears, some twine for tying and a plan.
To begin with a new and young plant, it is best to cut it down in the first winter to the one most rigorous stem. This will produce the main stem for the plant. After the second year of growth, cut back all but the 2 best shoots from the main stem. This will provide for the foundation of a good grape plant.
Once you have a nice growing grape plant, the best time of year to prune is late winter or early spring. Cutting grape plants will cause them to bleed sap, and cutting when the temperature is too warm will cause the sap to bleed too much. Before pruning, a grape plant may have up to 200-300 buds on it. General guidelines state that after pruning a wine variety of grape plant should have about 20-30 buds on it, and a juice or jelly variety should be left with 40-60 buds.
There are several different methods for pruning grapevines, each depends on the variety of plant and the style you wish to have. The simplest method is called the Kniffen method (sometimes called the cane method). This method has the main growing stem growing straight up, and then you train the lateral shoots to grow horizontally. There is a 4 cane method, where you will want to have 2 canes growing horizontally from each side, or the 6 cane method, where 3 canes grow from each side. The ideal grape plant pruned using the Kniffen method will have lateral canes 60 inches apart in height, allowing for good air circulation. To begin training the shoots for this method, you will want to construct horizontal wires about 60 inches in height and about 36 inches wide. When the first shoots have reached the wire you can prune all but 2 on each side, and then tie them to the wire with the twine. You will want to leave an equal number of renewal spurs; in this case 4 or 6 renewal spurs to allow next year’s growth. A renewal spur is one that has been cut back to 1 or 2 buds.
Another pruning method is referred to as Cordon pruning. Instead of producing different fruiting horizontal shoots each year, setting up a cordon pruning system produces permanent horizontal branches that can become very think over the years. Fruit does not come from the branches themselves, but spurs that grow down from the branches. These branches are grown on a T-shaped clothesline like support system and the 4 shoots are not removed each winter like the Kniffen method. Cordon pruning works well for many years, but some gardeners find that after a long period of time the permanent horizontal branches suffer from insect and mold damage and stop producing so well.
The Kniffen and Cordon method are the most common pruning methods used for grapevines. Some people may choose to cut their grapevines in a bush shape, by cutting all the branches to about 1 inch from the main stem every year. This makes the plant appear bushy, but the fruit trailers may be too close to the ground and ruin the fruit. The Espalier method has tiers of branches trained flat against a wall or structure. It is a very labor intensive method and although it has a very aesthetic look, it also can make the plant more susceptible to diseases. Using wire based frame work; it is also possible to train your grapevine into a fan shape using cutting practices similar to that of the bushy method.
Whatever method you choose for pruning grapevines, it is an important step to allow for the fullest extent of fruit production available. It can be both fun and interested and you will be rewarded for your work later in the season with a large fruit crop.