Left to right, Top: Regent, Gruner Veltliner, Pinot Noir Precoce. Bottom: Golubok, Rondo
Field trials of cool climate wine grape cultivars are beginning to identify varieties of potential for Washington State’s Puget Sound. For some varieties, field data have been collected for more than a decade, providing viticultural information. In more recent years, varieties showing potential have been made into wine for further evaluation.
In a maritime climate like Puget Sound, with annual heat units that range from 1400 to 2400 growing degree-days, matching the right variety with climate is critical to achieve optimum ripeness, flavors, and acidity in the wines. Though researchers have conducted grape variety trials at Washington State University’s Mount Vernon research center for more than 30 years, it’s been in the last decade or so that the search has intensified for varieties and rootstock combinations best suited for the region’s cool climate.
Gary Moulton, extension fruit specialist at WSU’s Northwestern Washington Research and Extension Center in Mount Vernon, has led variety and rootstock trials since 2000, testing some seven rootstocks and 40 cultivars and following some varieties through winemaking. Everson, Washington, tree fruit and grape grower Tom Thornton joined Moulton’s field trials in 2002 to provide a second and warmer location than Mt. Vernon for viticultural trials. Grapes in the trial are now made into wine through the wine technology program of South Seattle Community College.
Thornton, owner of Cloud Mountain Farm, a diversified farm in operation since 1978 that includes tree fruit, grapes, and a retail nursery, has worked with Moulton to plant more than 70 varieties. Cloud Mountain is about 30 miles northwest of Bellingham, and part of the Fraser Valley that begins in Canada’s British Columbia.
After the first few years of the field trial, Thornton said it became obvious that cluster thinning would be necessary on some cultivars to achieve a more accurate picture of what they could do. “For example, Zweigelt is a very large-bunched grape to ripen in western Washington. Some vines were producing 40 pounds of fruit per vine, and at high density plantings, we could never get past 17° Brix,” he said.
“But once we started cluster thinning, we saw very different results and got a better sense of what the variety can really do.”
The last three years at Cloud Mountain have been highly variable in terms of weather, Thornton said, adding that 2008 was the coldest year in 32 years, posting 1475 growing degree-days in heat units. The next year was the warmest and driest, breaking all records at 2400-plus growing degree-days, while 2010 was noted for its cold spring and seven inches of rain in September. Even still, the year logged more than 1900 growing degree-days.
Thornton shared the following data from promising varieties in his trial during industry talks at the Washington Association of Wine Grape Growers convention. Some varieties he discussed were to provide benchmark information. He noted that in western Washington, most vines are planted on rootstocks, unlike the own-rooted vines of eastern Washington, because of differences in ripening times. “We’ve seen huge differences in ripening in side by side plantings of some early rootstocks.”
Siegerrebe (Madeleine Angevine x Gewürztraminer)—White, aromatic variety that’s been grown in the region for 30 years. Susceptible to shot berries, needs good fertility management to avoid less than full bunches, has good disease resistance, with Botrytis bunch rot showing up only occasionally. Good producer, consistently cropping five tons per acre, but can slip to 800 pounds per acre if not managed properly.
Rootstock can improve cluster size.
Madeleine Angevine (Madeleine Royale x Precoce de Malingre)—Another tried and true white variety that’s been grown in Puget Sound for 30 years and used as a benchmark variety. Produces an average of five to seven tons per acre, Brix at 18.5, titratable acidity at 1.05.
Promising red varieties
Pinot Noir—Clones 71 and 72 have been planted in western Washington. Thornton is not convinced they are using the right rootstock and thinks ultimately the variety will be a winner year in and year out for the region. “There’s very little room for mistakes with Pinot Noir when grown on the west side.” He’s found that both canopy management and cluster thinning are important with the variety.
Pinot Noir Precoce—Ripens two to three weeks earlier than other Pinot Noir clones. Rootstocks are needed for the clone to ripen early, and the variety needs a warm site. Thornton is trying different rootstocks, including Schwarzmann, 3309 Courderc, and 1616 Courderc, to see if fruit can get riper. He believes Precoce shows potential for the region, though few test wines have been made.
Regent (German variety cross of