60 MILLION! Did you know that there are about 60 million vines in the Lodi Appellation that each receive individual attention from a skilled farm worker during the winter pruning season? Why do winegrape growers spend so much time, effort, and money pruning their grapevines?
In short, winter pruning is one of the most important cultural operations that occur in the vineyard as it sets the stage for the coming growing season. The decisions growers make while pruning affect the form of the vine, the vine balance (canopy vegetative growth and potential yield), and of course the quality of the fruit.
Old Vine Zinfandel, before and after pruning
Very simply, grape clusters (bunches), leaves, and tendrils are all attached to the shoot (think: new branches), and those shoots grow from buds each spring, which looks like the picture below. Those green shoots eventually lignify (turn rigid and woody) just before harvest each year, only to be trimmed down by growers during the winter. See here for a great explanation of grapevine structure and morphology on the Lodi Winegrowers webpage: http://www.lodigrowers.com/important-structures-features-of-grapevines/
A newly pruned spur with one bud
What’s really important to understand is that those green shoots and clusters which will pop up in the spring are already microscopically formed in each bud during the growing season BEFORE winter pruning. That means the number of clusters that will appear for the 2017 harvest are already formed in the vine right now! In fact, some people actually dissect buds in order to count and try to predict how large or small the upcoming crop will be.
In Lodi, the most common style of pruning is “spur pruning”. In both images here, the Chardonnay (left) is spur pruned on a bi-lateral cordon (two arms on a wire to accommodate machine harvest), and the old vine zin (right) in a “head trained” form.
Pruned Chardonnay and Old Vine Zinfandel
Spur pruning means we cut woody shoots (canes) down to a length of three inches, which typically includes two or three buds on each “spur”. In general, we predict a primary shoot will emerge from each bud, which will typically have two clusters, depending on variety. In this way, we calculate and plan how many buds we want to leave per vine, which gives us an indicator of potential yield. In a perfect world, leaving twenty, two-bud spurs on a Chardonnay vine should leave us forty shoots, each with two clusters, or eighty clusters for harvest. Of course, mother-nature has an enormous influence on the cluster number and size during the growing season, so it’s not quite as simple as described above.
3" spur with 2 buds
In addition to pruning the vine to meet yield goals, we also must leave spurs properly positioned and spaced from one-another. Crowding spurs together will cause shoots and clusters to grow too close together. This crowding of vegetative growth and fruit is not ideal, because it restricts sunlight and amble air movement, which are both absolutely necessary to produce high quality winegrapes.
Newly pruned row of Old Vine Zinfandel
Finally, pruning is absolutely a skill and an art form. As most things in viticulture and winemaking, it is an amazing marriage between science and art in order to influence that vine to produce a desired result. I have pruned many vines in my day, but not nearly as many as some of the incredibly skilled pruning masters that work with us at LangeTwins. When you pick up that glass of 2017 vintage LangeTwins wine, know that Step one to that tasty beverage was a dedicated team of skilled vineyard managers and crews working all winter long!
Vineyard Manager, Kyle Brown, pruning Old Vine Zinfandel