Pruning grapevines is a critical component of the grape production system. It is a relatively simple concept once learned, but many people who are unfamiliar with the process find it a little intimidating. The good news is the basic principles of pruning grapes are easy to learn and easy to apply even for those who are less experienced. Here’s our advice on how to prune grapevines:
There are several reasons why you must prune your grapevines. First, you want to control and regulate the number and position of shoots, cluster number, and size. During pruning you remove buds that would otherwise become new shoots in order to concentrate growth into the remaining shoots and clusters. If you leave too many buds, you will have a larger crop, which could be more than the vine could handle. Regulating the amount of crop will affect its quality and uniformity.
Second, you want the vine to maintain a consistent shape. You can train a grape vine to grow in different forms, sizes, and situations. Third, pruning improves fruit quality and optimizes the production potential. By limiting the number of shoots and leaves, you are working to maximize your crop yields without delaying maturity. Pruning will allow adequate growth for the following season.
Before you start pruning, you need to make sure you have the right tools. Most grapevines will only require a good pair of pruning shears. The pruning tool you use should be able to make a clean cut in the vine. A clean cut puts less stress on the plant and creates a less exposed surface area.
There are several different ways to prune, but we will focus on two: cane pruning and spur pruning.
Cane pruning is used for varieties with low natural fruitfulness on basal buds. It requires an annual replacement of the one year old canes (wood). The buds from these canes produce shoots that support the year’s crop.
The first step is to identify the fruiting canes for the next year. You want strong canes that are most likely to be fruitful, so look for canes that are round, well-matured, and developed on top of the vine that had plenty of light exposure during the last growing season. A healthy cane will be thicker than a pencil but no thicker than three times a pencil. With cane pruning, you will cut back about 90 percent of last year’s growth. You will also select another cane to be pruned back to one or two buds. This is the renewal spur that could have shoots arising for fruit cane selection.
Cane pruning does require a high level of expertise, is more expensive, and takes more time. You are required to make very educated choices about each and every vine. However, cane pruning has many advantages: frost protection, even production, and even spacing of growing shoots in the spring.
Spur pruning is used for varieties that show high fruitfulness on basal buds. It is the most effective and most popular method used. Grape varieties such as Cabernet Sauvignon and Merlot are most often spur pruned. Spur pruning is easy to do and easy to teach especially for vines that are trained on fences or trellises.
With spur pruning, you are trimming back the spurs on the vine to limit the growth. There are two fruiting canes that originate from each spur. The cane furthest away from the cordon is removed; the one nearest is shortened to produce next year’s spur. You want one to three buds on each spur.
You then select canes to be pruned back to form renewal spurs and prune those back to one bud. Then, remove any canes growing away from the fence or trellis. Try to space spurs a few inches apart on the cordon.
There are different training systems using spur pruning such as head-trained, spur-pruned vines and cordon trained vines. Each training system has been developed to make the best use of light, help develop fruit buds and ripen fruit, and give better air circulation.
So go ahead and don’t be afraid to cut back those grapevines! It looks drastic but your are assuring the health of the vine and the quality of your fruit.