Grape arbors provide a cool canopy during our long and hot summers, produce sweet grape clusters of fruit by early fall, yet usher in warm winter sunlight when dormant. My keen interest in training grapevines grew after meeting viticulturalists researching or implementing best practices in grape growing. From nurturing one grapevine to the installation of large vineyards, these researchers and growers shared their passion for training table and wine grapes. From them I learned that the most important steps to creating a well trained and productive grape arbor were to limit each vine to one trunk, allow the trunk to branch only above the arbor, and eliminate all flowers and fruit until the grapevine covers the arbor.
Dr. James A. Cook at the University of California at Davis was the first to inspire me. A picture of confidence based on years of vineyard trials and investigations, he taught our viticulture course where, during one of his lectures on pruning and training grapevines, he mentioned the unique shapes he had trained grapevines. His eyes gleamed when he embarked on his grapevine training projects.
He would start grape arbors by planting bare root grapevines with ample root systems because they promote vigorous growth needed for rapid training. In the spring, he would select the most vigorous cane and tie it to a column of the arbor then cut off all other canes. He would rub off or cut off all other new growth from the base and keep tying the one new shoot as it grows (every 6 to 10 inches) to encourage vigorous growth. His goal was to get the arbor covered with leaves and shoots as quickly as possible, without allowing unwanted plant growth that will have to be removed later anyway.
Standing under a canopy of shade created by an arbor can take me back to my encounter with a well trained grape arbor. It happened one afternoon when I walked out to the viticulture block of the university farm at Davis, California to locate the Winkler Vine mentioned in class. As I walked under the largest grapevine I had seen, I estimated the area it covered and put my hands around the trunk to guesstimate its circumference. Three hand lengths almost circumnavigated the trunk which supported this vine that covered the area of a classroom. I tried to imagine the one thousand pounds of grapes I was told this single vine produced annually. I saw myself someday training grapes over structures in the landscape.
That afternoon under the Winkler vine I learned I’d have to limit any vine to one trunk. Today, when asked to prune grapevines already trained over an arbor, I commonly find several trunks growing from the same root system. I limit young grapevines to one trunk to avoid congestion and competition that two or more trunks promote. Intertwined shoots and leaves compete for space and sunlight and quickly become difficult to thin out.
The Winkler Vine was named after the viticulturalist who singlehandedly standardized all the pruning systems used in California by comparing all the training and pruning systems practiced in his time. During that semester I met A.J. Winkler, a gentle man who was already a legend in the world of grape growing in California. One afternoon, in the hallway of the viticulture department at UC Davis, he graciously autographed my copy of “General Viticulture”, the bible for grape growing, where he only promoted the training systems that limited each grapevine to one trunk.
The following summer I found a job establishing a vineyard in potter valley. The owner, Guinness McFadden, had a passion for pruning and training grapevines. He described the annual pruning of a 100 year old grape vine trained over an arbor as a “dance” in that you lead or train the vine to grow and branch over your trellis or arbor.
Be sure to train your grapevine to branch at the top of your arbor. To do this, I allow the single shoot that will become my trunk to grow until it reaches a height 20 inches above the point I want the vine to branch. Then I cut it at that point. Grape buds are mature enough to start growing into lateral shoots twenty inches below the tip of any growing shoot. New growth will vigorously emerge and begin to grow over the horizontal supports of your arbor. I direct the vine’s growth above the arbor so that the main cordons (branches of the vine) run along the edge of the arbor and secondary cordons run perpendicular to the primary cordon and spaced at least two feet apart. It is on these cordons that arms and spurs will form with subsequent annual pruning.
Allow no flowers to develop into clusters of grapes until shoots and leaves cover the arbor. Many are surprised when I direct them to cut off all the flowers in the spring but eliminating fruit production allows the grapevine to use all its energy to envelop the arbor as quickly as possible. Without flowers or clusters of grapes all the energy produced or stored as starch is directed to new and vigorous growing shoots covering the arbor. Once the arbor is enveloped by growth, grape clusters can be allowed to form.
Japanese grape growers are experts at pruning and thinning fruit, their grape clusters contained very large berries. As a UC Davis graduate student I befriended Dr. Naosuke Nii, a plant hormone researcher from Japan. Later I visited him in Japan where I saw Japanese grape growers train their grapevines over arbors. They controlled the growth and vigor of their grapevines by constraining the root system. To limit the overall size of their vines to the dimensions of their greenhouses they dug out an eight foot cube in the ground and would compact the sides of the hole before back filling with top soil. The growers I met only produced one variety of grapes: Muscat of Alexandria.
Grape varieties that require being annually pruned back to two bud spurs, like the Flame Seedless variety, develop into the most attractive and uniform looking arbors. Grape varieties that require cane pruning, like “Concord” and “Thompson Seedless” are not only more difficult to prune for the novice but also less attractive when their conspicuous dormant canes are left for fruit production. I prefer spur pruned grape varieties for those new to training grapevines, especially over an arbor or pergola. We trained our grapevine trunks to branch into two cordons above the arbor whose arms are annually pruned back to two bud spurs.
California is known to have had one of the longest arbors. The Hearst Castle in San Simeon, according to interpreter Constance Gordon, at one point had a columned arbor (or pergola) one mile long covered by a thousand grapevines. Fruit trees espaliered along the sides of the tall pergola enclosed the cool green tunnel designed to provide shade, and the seasonal grape cluster, to those strolling and even those in the saddle. Covering this long structure as quickly as possible with shade producing grapevines would have required the same basic steps: Limiting each vine to one trunk, allowing the trunk to branch off into cordons only after it grows over the structure, and eliminating all flowers and grape clusters until shoots and leaves cover the structure.