Can Washington Growers Use Rootstocks and Maintain Fruit and Wine Quality?
Almost all wine grapes grown in Washington are grown on their own roots. That’s unusual. In most of the world’s other major wine regions, grapes are grown on grafted rootstock. That is, varietal scions (the part of the plant that produces the leaves, buds, and fruit) are grafted onto rootstocks resistant to phylloxera–a tiny sap-sucking insect–and nematodes–microscopic worms that may attack the roots of vines. For a variety of reasons–mostly unknown–Washington vineyards have not yet been plagued with phylloxera and nematodes. The operative word being yet.
The spectre of a vine-destroying invasion has been lurking in the shadows of Washington vineyards for years. What if, wine industry professionals have fretted, growers did have to start using rootstocks in order to beat the insects and worms? Would grafting affect wine quality? Are Washington wines great in part because their grapes grow on own-rooted vines?
No Differences Detected
An international group of researchers examines the research vineyard at WSU's Irrigated Agriculture research and Extension Center in Prosser. Photo: Washington State University; high resolution versions available upon request.
Answers to those questions have been years in the coming and required a monumental, multi-year effort on the part of Washington State University researchers. A team of scientists led by WSU viticulturist Markus Keller just completed a set of projects that their predecessors began in 1999, with results published in a pair of papers in the March issue of the American Journal of Enology and Viticulture.
“The short answer,” said Keller, the Chateau Ste. Michelle Professor of Viticulture based at WSU’s Irrigated Agriculture Research and Extension Center in Prosser, “is don’t be afraid.”
Enologist Jim Harbertson, an associate professor also based at the Prosser station and a cooperator in the study, agreed. “The big push back 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.”
Climate, Not Rootstock, an Influence
Keller pointed out that since Washington growers use deficit irrigation–controlled amounts of water–to manage vine vigor, there were also no differences in canopy size. “Water deficit overrides any vigor-promoting influence a rootstock might exert in wetter climates.” 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 excellent 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 driving 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.”
Technicians at the WSU research winery in Prosser bottling wine made from grapes grown on scion's grown on rootstocks commonly used in commercial-scale vineyards. Photo: Washington State University; higher resolution versions available upon request.
Three Varieties tested over Three Seasons
The advice to “have no fear” of grafting comes from data collected over three growing seasons, with three wine-grape varieties–Merlot, Syrah, and Chardonnay-–evaluated on six common, commercial rootstocks as well as on their own roots. One rootstock failed the trial because it over-wintered poorly and was deemed unsuitable for use in Washington’s growing environment. Once the research vines were established, wine was made from each grape/rootstock combination for three growing seasons, and then tested for multiple indicators of quality, including those critical to red wine quality.
Results of this complex, long-term experiment are published in a pair of papers, one focused on plant vigor, yield formation, and fruit ripening, the other on grape and wine composition. The viticultural results show that variations are due to “scion cultivar, spatial differences across the vineyard site, and climate variation 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.”
Own-rooted Vines Recover Better
Fortunately, right now, there is no reason for eastern Washington growers to switch to grafted rootstocks. Indeed, for economic reasons, it is better to stay with own-rooted plants wherever possible. “When we have a freak cold snap, and eastern Washington sees these periodically, vines can die to the ground. Grafted vines would need to be regrafted because the graft point sits above the ground, while own-rooted vines will likely recover on their own.” Regrafting is expensive and, indeed, grafted vines create higher initial startup costs, because they are more expensive for nurseries to produce.
But, Keller cautioned, eventually there will likely be cause for Washington growers to move toward grafted vines. “Nematodes build up in the soil over time,” he said, “so increasing numbers of second or third generation vineyard plantings will likely need to be on grafted vines.”
As for why Washington has, for the most part, not been scourged by phylloxera, the sap-sucking insect that plagues nearly every other growing region, he said no one knows. “Some think it is our cold winters – but …Germany, Switzerland and Canada have problems with phylloxera. It may be that our dry soils make it hard for the insect to spread.” But for that Australia offers a cautionary tale, he said, as trucks and mechanical harvesters are likely the cause of the spread in the dry soils there. “A few insect eggs could have been caught in tractor tires and spread from one location to another.”
Both scientists said that a large team has worked for years on the own-rooted versus grafted experiments. Bob Wample, a longtime leader in viticulture both at WSU and then at Fresno State University in California, initially planted the vineyard blocks. Sarah Spayd, now at North Carolina State University, was also one of the originators of the experiment. 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 years and contributed essential expertise to the projects. The WSU Agricultural Research Center, the Northwest Center for Small Fruits Research and the Washington Wine Advisory Committee helped fund it, while donations of plant material came from Ste. Michelle Wine Estates and Inland Desert Nursery, and Quiedan Company donated trellis materials.
“This type of experiment has never been done before on this scale and with this many variables,” Harbertson said. “It was huge and complex. The methods and results truly reflect Washington’s unique conditions.”
“We now know that if we ever have a problem with phylloxera or nematodes, we have the rootstocks to choose from that work in the growing conditions here,” added Keller. “They and many more are now also in our clean plant program, so we’re ready if growers wish to start using rootstocks.”
By continuing to use science-based solutions, techniques and management strategies, we know that Washington’s reputation for producing premium wines is safe and can continue to grow.
–Brian Clark
For more information on WSU’s viticulture and enology partnerships with the Washington wine industry, please visit http://bit.ly/wsuveext.
The papers discussed in this story are available at the Journal of Enology and Viticulture website. For the abstract of “Rootstock Effects on Deficit-Irrigated Wine Grapes in a Dry Climate: Vigor, Yield Formation, and Fruit Ripening” by Keller, Harbertson and Mills, please visit http://bit.ly/GUJUeU. For the abstract of “Rootstock Effects on Deficit-Irrigated Wine Grapes in a Dry Climate: Grape and Wine Composition” by Harbertson and Keller, please visit http://bit.ly/GUKfyg.
Taste Washington and Auction of Washington Wines
Auction of Washington Wines Celebrates 25th Anniversary, Partners with WSU
Auction of Washington Wines joins forces with Washington Wines Festival and Washington State University’s Celebrate Washington event to create a collaborative fundraiser in celebration of the Auction’s 25th anniversary. The auction continues to benefit Seattle Children’s Hospital, as well as the Washington Wine Education Foundation.
“No world-renowned wine region is without a prominent university partnering in its success. The Northwest is no exception,” said Ted Baseler, chair of WSU’s Campaign for Wine and president of the Auction of Washington Wines board of directors. Washington State University has provided critical help with science-based solutions to grape-growing and winemaking challenges. “In the 10 years of the Celebrate Washington Wines event, we have provided over $1 million to the Viticulture and Enology program, transforming it into one of the largest in the United States,” said Nancy Harnasch, past chair of the event. WSU will be represented on the Auction of Washington Wines Chairman’s Committee for the 25th Anniversary celebration.
The Auction of Washington Wines is comprised of five events including Revelry at Col Solare in the Tri-Cities area (Spring 2012), Picnic & Barrel Auction at Chateau Ste. Michelle Winery (August 16), the Winemaker Dinner Series at various locations throughout the Puget Sound region (August 17), Covey Run and The Wine Gala at Chateau Ste. Michelle Winery (August 18).
Since its inception in 1988, the Auction of Washington Wines has raised more than $26 million for uncompensated care at Seattle Children’s Hospital, whose core mission is to provide exceptional care for every child in the region, regardless of a family’s ability to pay. A portion of the money raised also benefits the Washington Wine Education Foundation which aims to strengthen the quality and reputation of the Washington wine industry by providing support for WSU’s world-class viticulture and enology research and Extension, education, and training programs that meet the specific needs of the Washington wine industry.
"I hope you'll join me at Taste Washington. We'll be in the Vineyards section. I would love to chat with you about our science-based educational opportunities in viticulture and enology, and what it takes to keep Washington wines among the world's best." – Thomas Henick-Kling, director, WSU Program in Viticulture and Enology
Funding directed to the Washington Wine Education Foundation goes toward research in viticulture and enology, Washington-based educational programs that promote undergraduate and graduate degrees, and to farm worker and industry employee programs that promote health and safety. This educational group began collaborating in 2001 to create quality educational programs in grape growing and winemaking.
The 25th Auction of Washington Wines is chaired by the industry’s finest. Bob Betz of Betz Family Winery, and Stein Kruse, president and CEO of Holland America Line and chairman of Seabourn, are the 2012 Auction co-chairs. Rick Holley, president and CEO of Plum Creek Timber Company, will lead the efforts of rallying past chairs.
For more information about Auction of Washington Wines, please visit http://bit.ly/auctionwashwines.
WSU V&E is at Taste Washington This Weekend
Taste Washington weekend features fun and educational wine seminars on both Saturday, March 31, and Sunday, April 1, at CenturyLink Field Event Center. These seminars are led by top national wine personalities and sommeliers. Topics for the seminars showcase various aspects of Washington wine, as well as wine and food pairing demonstrations by renowned local chefs.
For more information on Taste Washington, please visit http://bit.ly/tastewashington.
WSU Mediterranean Cruise Helps Support Viticulture and Enology Education
Wine. Wind. You.
Cruise the Mediterranean and sip premium wines in luxury.
This May, a small, select party will set sail aboard the luxurious Windstar Wind Surf to cruise the Mediterranean. Will you be on board?
Join Washington wine and food celebrities as they sail the Mediterranean on a private chartered cruise, May 28 – June 2, 2012. Embark from Nice, France, and call at Portofino, Cinque Terre, Livorno, Portoferraio, and Rome.
Chateau Ste. Michelle culinary director John Sarich and head winemaker Bob Bertheau, Jeff and Vicky Gordon of Gordon Estate, along with world-renowned wine expert Thomas Henick-Kling will wine, dine and educate you in elegant style.
Enjoy being pampered on a small ship in the fleet of one of the world’s best cruise lines. You’ll enjoy:
- All meals and snacks aboard ship, including special gourmet wine tasting dinners prepared by our celebrity chef.
- Featured wines poured throughout the cruise along with tasting events and winemaker seminars.
- Parties aboard ship and live entertainment every night.
- Excursions to the most beautiful and historic ports of call on Italy’s beautiful Mediterranean coast.
- Only 146 freshly redesigned cabins are available for this exclusive wine lover’s expedition.
Learn more at http://bit.ly/cruisewine.
Tags: fruit quality, Jim Harbertson, Markus Keller, wine quality
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