Good Fruit Grower

August 1

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8 AUGUST 2015 Good Fruit Grower C abernet Sauvignon is one of the top two wine grape varieties produced in Washington State. But in some vintages the late-maturing grape can be a challenge to ripen properly in cool and warm sites. Sometimes, a variety and site are perfectly matched, and the growing season is ideal, like Goldilocks' por- ridge—not too hot and not too cold. But more often, growers must deal with an array of issues while striving to produce quality fruit. Late-season Bordeaux varieties, like Cabernet Sauvignon, can be par- ticularly challenging as growers wait for fl avors to fully develop while worrying about fall rain and frost. Two factors determine the relative warmth of a vine- yard site: heat accumulation and length of the growing season. Heat accumulation, expressed as degree-days, is measured by taking the average of the maximum and minimum daily Fahrenheit temperatures, subtracting 50 degrees, and then adding them together over an entire growing season. Wine grapes need at least 1,700 degree- days to adequately ripen, but if the climate is too hot, with more than 3,500 degree-days, fruit acidity and quality is reduced. Generally, 2,700 to 3,000 and above are consid- ered moderate to high heat units and 2,300 to 2,700 are considered low to moderate heat units. A growing season of 150 to 180 frost-free days is needed to ripen the fruit. Jason Schlagel is not as concerned about a cool site's potential for frost. He's more interested in the length and quality of the ripening period provided by the cool site. Schlagel is chief agriculture officer at Taggares Fruit Company and co-owner of the cus- tom farming company Sierra Vista Farm Management, headquartered in Pasco, Washington. Taggares Fruit has extensive tree fruit and grape acreage in the Columbia Basin. Schlagel has viticultural experience in both warm and cool sites. Before joining Taggares, he spent four years at Milbrandt Vineyards, a company with wine grapes in the warm Wahluke Slope and cool Ancient Lakes appellations and four years with Ste. Michelle Wine Estates, based in Paterson. Canopy "Our biggest challenge in a cool site is getting the vineyard canopy growth under control," he said during a meeting of the Washington Association of Wine Grape Growers. "But it's just the opposite in warm sites." Irrigation is a key tool he uses to manage canopy growth. Schlagel monitors the evapotranspiration (ET) rate in his vineyards daily. ET is the loss of water from the soil though evaporation and the plant's transpi- ration. "ET numbers are generally lower in cooler sites than warmer ones," he said. "We have a hard time with Bordeaux varieties, like Malbec, that have big berries, because in cool sites it's diffi cult to achieve the small berry size that the winemakers want." He noted that last year, some of his cool site vineyards received only four to fi ve inches of water per acre foot for the season. "We fi nally got control of the canopy in some blocks by August." On the fl ip side, the challenge presented by warm sites is growing enough canopy and providing enough irriga- tion without stressing vines too much. Schlagel develops canopy and production targets in each vineyard, assigning target numbers to everything from pruning bud counts to shoot length to number of clusters. "We do everything we can to hit those targets," he said. In cool sites, he thins shoots more aggressively and generally has higher disease pressure compared to warm sites. Additional fungicide sprays are often needed in cool sites. "Generally, in a warmer site, the winemaker wants excessive shoot thinning to develop thick skins on the berries and less methoxypyrazine, or green fl avors," he said. When Cabernet Sauvignon is grown in a cool site, a Warm and cool site Grapes CHALLENGES Yield management is critical when growing Cabernet Sauvignon in a cool site. by Melissa Hansen "Our biggest challenge in a cool site is getting the vineyard canopy growth under control. But it's just the opposite in warm sites." —Jason Schlagel

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