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GRAPE GRO WING against grafted rootstocks in Washington has been the fear that wine quality won't be as good. But what we saw is that, for all practical purposes, there is no difference." Keller pointed out that since Washington growers use deficit irrigation (controlled amounts of water) to manage vine vigor, there were no differences in canopy size. "Water deficit overrides any vigor-promoting influence a rootstock might exert in wetter climates," he said. In other words, growers will be able to continue using the vineyard- management techniques they've already mastered, even if they grow grafted vines. "It's the climate, not the rootstock," Keller said, referring to Washington's excel- lent reputation for producing high-quality fruit. "The differences we did see over the course of this experiment had to do with vintage." Both scientists said that their multi-year experiment confirms that scion, vineyard location and vintage are the driv- ing factors of grape and wine quality, and pointed out that this is something growers and winemakers already know. "We just need to be reminded once in a while." Three seasons, three varieties The advice to "have no fear" of grafting comes from data collected during three NORTHWEST BC WASHINGTON Seattle WSU Yakima Prosser OR growing seasons, with three winegrape varieties—Merlot, Syrah and Chardon- nay—evaluated on six common commer- cial rootstocks as well as their own roots. One rootstock failed the trial because it over-wintered poorly and was deemed un- suitable for use in Washington's growing environment. Each year wine was made from each grape/root combination, and it tested for multiple indicators including those critical to red wine quality. One of the papers resulting from this complex, long-term experiment is focused on plant vigor, yield formation and fruit ripening; the focus of the other paper was Spokane Extension Center Walla Walla ID grape and wine composition. The viti- cultural results show that variations are due to "scion cultivar, spatial differences across the vineyard site and climate varia- tion among years." In other words, the dominating factors affecting grape growth are vintage and vineyard site and soil variability—not rootstock. Likewise, the enological results "showed that rootstock caused few significant differences in fruit and wine composition and, instead, the dominant variables were scion and, to a lesser extent, vintage." Team worked for years Both scientists said that a large team has worked for years on the own-rooted versus grafted experiment. Bob Wample, a longtime leader in wine science both at WSU and then at California State Univer- sity, Fresno, initially planted the vineyard blocks. Sarah Spayd, now at North Caro- lina State University, also was one of the experiment's originators. Keller's former Australian graduate student, Shayne Hackett, grafted scions to rootstocks in 2002. Many other members of WSU's technical staff as well as graduate students mentored by Keller and Harbertson have been diligent data collectors for many TRY BEFORE YOU BUY – CONTACT YOUR LOCAL REP TODAY FREE TRIAL OF OUR NEW TANKJET® 55 BARREL CLEANER SUPERIOR SPRAY. SERIOUS RESULTS. TankJet 55 barrel cleaner for cleaning barrels up to 5' (1.5 m) in dia. Take advantage of this risk-free offer to try our new TankJet 55 barrel cleaner in your winery. You'll experience benefits like these: • Powerful cleaning using low flow rates to prevent toast removal and reduce water and chemical use • Fast cycle times enable cleaning of multiple barrels in minutes • Durable construction and use of wear-resistant materials extend service life • Easy to use – compatible with most pumps and pressure washers Try the TankJet 55 today! Call 1-800-95-SPRAY or visit TankJet.com. WINES & VINES AUGUST 2012 49