Seasons in the Vineyard: Pruning for a prime vintage
No matter the climate, vineyardists around the world face similar tasks to produce the right combination of quantity and quality of grapes from their vines. The tasks of keeping a vineyard are some of the most labor intensive work-by-hand that still exists in modern agriculture.
There is pruning from late November to early April, tying from mid March to late April, weed control from early May through August, disease and insect control from early May through harvest, canopy management from mid June through August, crop assessment from early August to harvest, and finally harvest itself from late August into November. Beyond these major tasks, there are also incidental jobs to do in the vineyards, such as chopping up the brush after pruning, mowing the row middles, trellis repairs, etc. (And we won’t even go into all the work of winemaking in this series.)
Vineyardists of the northern climes face greater challenges when it comes to winter than their counterparts in warmer, less volatile climates. That harsh beginning of the year requires the first, and perhaps most crucial decision making by vineyard workers in determining the grape harvest for that year. Pruning, the cutting back of the previous years’ growth by 80 to 90 percent, is a complex process of evaluation, calculation, estimation, combined with old-fashioned experience and hard work.
Mike Collizzi and Steve Lerch of the Cornell Cooperative Extension’s Finger Lakes Grape Program recently conducted a workshop at the Finger Lakes Community College’s Teaching Vineyards at Anthony Road Wine Co., to help existing and aspiring vineyardists improve their pruning technique and their overall knowledge of viticulture. Only about half of the 30+ people who signed up for the workshop were willing to brave the barely double digit temperatures and the deep, crusted snow, but true vineyardists are unbowed by such conditions when it comes to the care of their vines.
Despite the cold winter on top of last year’s severe cold damage, Colizzi remains optimistic, and with reason. “This winter may have been colder than last winter, based on the overall average temperature. However, we have not been seeing as severe damage as we saw last year,” he says. “This is because it got cold and stayed cold, we did not experience the temperature swings like we did last year. As the vines go through winter, they are constantly adjusting their hardiness based on the air temperature. As it warms up, the vines become less hardy, and as it gets colder, the vines become more hardy. We get into issues when it warms up for a couple days and then gets cold again. At this point, I expect to see minimal damage to varieties like Riesling and Cabernet Franc. The samples I have taken all show pretty good survival.”
Colizzi has heard reports from growers who have seen greater damage in more sensitive varieties such as Gerurztraminer and Merlot, however he has not sampled those himself yet.
Bud damage evaluation is done before and during pruning. “If a grower had vines that sustained significant damage they could leave more buds on them when pruning to help offset the potential loss from cold temperatures,” says Colizzi. As sample vines are pruned, based on a bud count estimate for that variety and size of vine, the cuttings are weighed. Those samples give a baseline for pruning the rest of that vineyard, with adjustments for each vine’s size and condition.
“An example would be 2 lbs. of Chardonnay cuttings with 50 percent damage. Using the 20+15 bud formula for that variety and the weight of the cuttings, the grower would calculate that they should leave 35 buds total with no damage, but with 50 percent damage, they should leave an extra 17 buds. The grower would now have to prune the vine to 52 buds total,” says Colizzi.
Different varieties are trained on the trellises in three basic techniques: Top Wire Cordon (two arms) and Umbrella (arms trailing downward) for varieties of grapes with a downward growth habit, and Flat Cane (or Vertical Shoot Position, VSP) for varieties with an upward growth habit.
The person doing the pruning must be able to make decisions for each vine’s unique situation. Colizzi says achieving that calculated optimal number of buds can sometimes be hard to achieve on the standard two-tiered Flat Cane trellis because space is limited, and overlapping of canes is not desirable. “To combat this problem growers will sometimes have to switch to a Low Cordon training system with long spurs for that year. They can then go back to the flat cane system in the following year.”
Ultimately, Colizzi and Lerch say the goal of pruning is to achieve balance in the vineyard; a balance between fruit production and the foliage that supports the fruit as well as the survival of the vine.
YCCCE will have two pruning workshops again next year; one in late fall and one in early spring.