Overcoming ripeness challenges
Growers can use several tools to manage the canopy and crop load to help ripen their grapes.
Crews should be instructed to clean out spur congestion, as shown by the pocket knife, during pruning.
With few perfect vineyards in the world, growers must learn how to manage what they have to achieve grape maturity. By zeroing in on canopy, irrigation, and crop management strategies, underperforming or problematic vineyards often can be turned around, resulting in grapes that ripen in a timely manner and meet the winemaker’s expectations.
Rick Hamman, viticulturist for Hogue Ranches and Mercer Estates, has been involved in the wine grape industry for more than two decades, working as the liaison between wine companies and growers. He recently shared practical management strategies to help eastern Washington growers set up their vineyards for harvest success.
Hamman defines canopy management as choosing the trellis system that will allow quality sunlight and protection from sunburn on the west or south side, pruning accurately to adjust crop load and reduce spur congestion, and removing clusters from weak shoots.
Pruning directions need to be communicated with the vineyard crews to ensure that workers take the time to reduce spur and canopy congestion and are not just busy counting spurs, he said during the recent grape ripeness seminar sponsored by the Washington Association of Wine Grape Growers.
It’s important to remove the noncount, nonpositional shoots that will cause canopy congestion later on, he said. “For the amount of money you’ll spend in shoot thinning, it’s an efficient way to open the vines and get the shoot and spur positions that you want. If you run out of time during pruning, you can do shoot thinning later, but it is more expensive.”
Eastern Washington vineyardists are fortunate that they have the ability to control irrigation and can use regulated deficit irrigation to control canopy growth. He encouraged growers to use technology (soil probes, pressure bombs, soil moisture monitoring systems, and such) to assess the amount of soil moisture they have in their soil profile and how much water the vine is using.
Regulated deficit irrigation, a common practice among eastern Washington growers, is predicated on having adequate soil moisture through flowering and fruit set and then shifting to a maintenance mode from veraison through harvest. After harvest, the vineyard should be fully irrigated to fill the soil profile before winter. Some growers have taken the stress too far, drying soil during fruit set and have negatively affected their yields.
“If you have active growth at veraison, you want to shut the vines down and get to the static position,” Hamman said, adding that seeing yellow leaves—as long as they don’t fall off—is not necessarily a bad thing.
He prefers drip to sprinklers (under or over vine) because moisture tends to be more uniform with drip, especially in areas with wind and slope. “But you need to recognize vineyard areas with high or low vigor and add more tubes, emitters, in-line valves to equalize things.”
Growers should also be aware if there are subsurface drainage issues—like being on the downside of a canal—that prevent the soil from drying down.
Poor irrigation management can result in poor fruit set and yield loss from too little water applied. But there are a lot more problems from too much water—large berries and clusters, congested canopy, shading, additional expense for leafing and shoot removal, increased disease, more hang time required to ripen fruit, green vegetal flavors, and more sorting.
On balanced vines with the proper crop load, grapes should ripen in a timely manner, he said. “More clusters equal more hang time.”
Crop management is a balancing act between crop size, balancing the vine, adjusting the crop to the vineyard yield target, and timing harvest to supply the winery’s needs based on tank space and wine style and tier.
If crop load needs adjustment, the timing of cluster thinning does make a difference, Hamman said, adding that he’s had some growers thin right before harvest.
Based on three years of Merlot and Cabernet Sauvignon field trials, Hamman found that the best time for cluster thinning was around veraison. “If you wait later or do it earlier, you can have other issues,” he said, adding that Brix was highest when grapes were thinned at verasion compared to pea size, four weeks postveraison, or no thinning.