Pruning Season..the beginning. When I think of pruning season it brings up visions of mustard grass and the changing of the vines into organized structures. This is the beginning of what this year’s grapes will become. Yet pruning is so much more. When the grape vine is pruned it not only influences the crop for this year, but the next as well. The most important operation during the dormant season is pruning. Pruning of grapevines is recommended anytime after the vines leaves have fallen. In Sonoma County this occurs late fall to early winter. Once the leaves fall, the vascular system becomes inactive and plugs up. Before this time, minerals and carbohydrates are transferred from the leaves into the permanent, woody structures of the vine for winter storage. There are various types of pruning methods. Which pruning method one chooses depends on the type of grape varietal you have and which system is the most efficient to your production. It’s important to know that fruit is only produced on shoots growing from one-year-old canes. Therefore, healthy new canes must be produced every year to maintain annual production of fruit. Wine grapes are generally trained to have two or four permanent cordons or arms and are spur (short bearer) pruned. Within each method the same thought process exists. The removal of last year’s woody (lignified) growth on the grape vine to stimulate new growth and fruitfulness, but also for controlling yield and timing of growth. The vine if left alone would produce expansive vegetative growth and an abundance of extremely small clusters of fruit. That end result would be inferior grapes for the winemaker to work with. Remember the old saying: you can make bad wine from good grapes, but you can’t make good wine from bad grapes.
Going back to the system. The most common system of vine training (trellising) is undoubtedly the Vertical Shoot Position, or VSP system. This system of trellis is the most suited to mechanization and ease of tractor use.
The two most common styles of canopy (the green parts of the vine – shoots and leaves) management that lend themselves to VSP trellising are cordon pruned and cane pruned. There are different ways of trellising the vines while incorporating these two pruning styles. These differences are in the number of cordons or canes (arms) that are trained for fruit production.
One other system of pruning that is common in California is the head-trained spur pruned one. Here, there is no elaborate network of stakes and wires to support the vine and its growth. The vine is allowed to flop like an umbrella about the trunk. The fruit hangs underneath the shade of this umbrella. Many of the old-vine Zinfandel vineyards are trained and pruned in this system. Newer plantings are rarely done to this style as it does not lend itself to mechanization and will always require hand labor for all its operations.
The choice of style of trellis and pruning method that best suits the individual vineyard’s site. Among the things that are taken into account are both the vigor ( the rate of shoot growth) of the variety and rootstock, soil type. One might choose a spur-pruned cordon system where there is sufficient vigor and fruitfulness. Some of these grape varieties are Cabernet Sauvignon, Merlot, Sauvignon Blanc and Syrah. Cane-pruning might the choice in situation where vigor is limited used most frequently with low vigor varieties such as Pinot Noir, or fruitfulness of the basal buds on the cane is questionable. Typically cluster sizes are larger with cane pruning than cordon pruning which may figure into ones decision. With this method two healthy canes from the previous year are selected – the rest are cut off – and carefully wound around and tied to the trellis wire extending in opposite directions from the vine trunk. Cane pruning ensures that the growing shoots will be evenly spaced in the spring; it also allows sunlight into the canopy when a vertical trellis is used, and some growers like it because the fruit grows from new wood every year.
Whatever the pruning method used its importance to the final product you pour into your glass is immeasurable. Not only in the decision making of the process, but its execution. The workers that perform this what, I consider an art form spend years learning their skills and honing proper pruning techniques. Yes as with any skill when the work is done there is competition. Here are some photos from this year’s 16th Annual Sonoma County Pruning Championship held February 13th at Shone Farm. Check out more on this year’s pruning competition at our Facebook page.