To Prune or Not to Prune
Spring is upon us; soon vines will be budding and grapes will begin to grow. This pivotal moment is the official start of the growing season for vintners. But vineyard workers have been working all winter to prepare for bud break. In our recent conversation, Oregon-based vigneron and vineyard worker Jessica Miller spoke at length about what winemakers and vineyard hands do in the winter to prepare for spring. “The wintertime is all pruning. That is the bulk of the work. Pruning is pretty much a 9-5 for everybody.” But an immense amount of knowledge and technique is required to prune effectively. Jess’s experiences at Clos Roche Blanche in the Loire Valley, De Moor in Chablis and Inglenook in Napa provide unique insight into this tremendously important aspect of vineyard maintenance.
Jess’s first in-depth experience with pruning was with Julien Pineau, who took over Clos Roche Blanche in 2014. She spent a month working one-on-one with Julien learning the basic elements of pruning. There are two primary techniques used to prune vines. The first is called cane pruning. In cane pruning, workers prune at the head, the “V” that forms at the top of the trunk. This allows canes, the branches that grow from either side of the trunk, to grow anew. The second technique is called spur pruning. Spur pruning preserves canes from previous years on the wire; old vines growing from the canes are removed to make room for new vines to grow. Jess also described a less popular technique called gobelet pruning, which does not rely on wires. The trunk is kept short. Gnarled wood from years of spur pruning remains at the head. From there, vines grow upward in a goblet shape. This type of pruning is better suited for arid climates with less risk of rot.
Vines must be pruned before bud break but the precise timing of pruning is not crucial. While Jess was a cellar intern at Ingelnook in Napa Valley, they ran a pruning trial. They pruned some vines in late November and some in late March. To her surprise, “the phenolic* and the sugars and the acids have caught up by harvest”. The timing did not affect the quality of the grapes.
However, after bud break, frost can damage the vines. Different techniques mitigate the impact of post bud break frost. “In New Zealand it’s ridiculous,” recounted Jess, with a laugh, “they get helicopters out there to blow the air around.” For a more fiscally conservative vineyard owner, there are pruning techniques that can help protect against frost. Jess described a technique that she first witnessed in cooler climates in France and that she now sees every day from her home in Oregon, which overlooks 30-50 acres of St. Innocent vineyards where the same technique is employed. With this technique, pruners leave a third cane on the vine, slightly higher than the other two canes. In the case of a late frost, the lower hanging canes will bear the burden of the cold and spare the higher cane from damage.
In her pruning work, Jess is primarily concerned with trunk disease. She first became aware of the severity of trunk disease when working with Alice and Olivier de Moor in Chablis. The disease had affected 60% of the couple’s vines. Luckily, they came across researchers in Sancerre who had written a manual on how to avoid trunk disease. “By the way that you prune,” said Jess “you can create a habitat – or not – for trunk disease.” Incorrect pruning produces dead wood and dead wood is a host for trunk disease. There is a common misconception that rain is the primary vector for the disease, however research has shown that it is improper pruning that leads to the three fungi that cause the disease. “In Oregon no one had even heard of it,” said Jess. She has since passed on techniques for preventing trunk disease to others who have come to learn how to prune with her. Recently, she found someone who is willing to translate the manual to English and publish it in the U.S.
Though pruning fascinates Jess, she says that her favorite part of the winter season is reflection and preparation. “The sun sets so early! You can only work so long in the wintertime. It’s great for farmers because when you have days that are over 12, 13, 14 hours long you tend to work as long as the sun is up so I think that ability to plan in the winter is really nice.” Alas, those days of quiet contemplation are numbered. With spring will begin long days in the vineyard carefully nurturing grapes for a new vintage.
* One of the most important groups of compounds in wines are phenolics, which are derived from phenol, and are responsible for structure and color in red wines. Tannin and anthocyanin are examples of major phenolics found in wine.