Waiting for Guyot: It would be reasonably accurate to point to Bud Break as the start of the annual grape growing cycle in Oregon. This is the time period in the Spring when the buds on a vine first burst forth with the tips of the green shoots that ultimately form the canopy. But the work in the vineyard in the Northwest actually corresponds closer to the beginning of the calendar year, in January, with the start of pruning.
No one knows exactly when man figured out that grapes benefitted from the cutting off of old vegetation, but the practice was known in ancient Egypt and well established by the Roman era. It took a Frenchman named Dr. Jules Guyot, however, to evaluate and then promulgate a system in the late 19th century that is most widely used today. The technique involves the selection and retention of two of the old shoots, or canes, which extend from the main trunk and which remain from the prior year, and the cutting off of the other old canes on either side of the trunk. When the two shoots are laid horizontally, extending in either direction from the trunk, and then tied to the lowest wire on the trellis, this then constitutes what is known as a double Guyot system of pruning. The picture below shows the two remaining shoots after the pruning but before the shoots are tied to the wire. The rest of the old vegetation is “pulled” from the trellis and laid in between the vine rows, where it is later removed or chopped up and culitvated back into the soil.
The selection of which two older shoots, or canes, to retain can be important to how the canopy of leaves eventually develops. There are nodes on the canes which indicate where this year’s new shoots with spring from. Ideally you would like to pick canes that have nodes that are about 5-6 inches apart, about the width of a person’s fist. Any wider and there will be fewer shoots and fewer clusters per lineal foot of trellis, which makes for inefficiency and loss in terms of final productivity. Any closer together, and the canopy might become too dense and crowded, with too many shoots in a smaller space, which in turn creates a canopy of leaves that does not allow sufficient light to reach the clusters. With too many shoots, more clusters will develop, but then the vineyard manager will have to decide whether to thin crop more aggressively or run the risk that there are too many clusters on each plant which prevent the plant from ripening the fruit optimally. While these parameters are the norm for Oregon, other factors will influence the ultimate balance the vineyard manager is trying to maintain in a specific vineyard between vine health, grape quality and overall productivity. Those factors include how warm the site is, how far apart the vine rows are and how far part the plants within the row are, as well as the vigor of the site and even the grape variety being grown.
Tying the two remaining canes to the wire is usually left until the weather is warmer, since attempting to bend them when they are cold and brittle could cause them to become damaged or broken. The pruning work can continue through the vine’s dormant period, but general practice is to try to finish the work no later than a week or two prior to bud break. This avoids bleeding, the loss of water from pruning wounds, which can occur if pruning is too close to bud break, and its also avoids damage that may be done by the pruners to the emerging buds.
Most vineyard managers may well argue long and hard about the nuances of pruning. They might for example, disagree about how many buds to leave per cane, whether to use single Guyot or double Guyot pruning, or what the significance is of the weight of the pruned material. But there is no disagreement of the critical importance of the task. Pruning can either set the vineyard up for success for the ensuing growing season, or it can create a foundation for the growth that can lead from one eventual problem to another. And we no longer need to wait for Godot, of for Guyot, to tell us that.
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