Left to right, Top: Regent, Gruner Veltliner, Pinot Noir Precoce. Bottom: Golubok,   Rondo

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 [Sylvaner x Muller Thurgau] x Chambourcin)—Has one-eighth Labrusca parentage. “Very experimental, but is very promising and looks to be the best variety in Puget Sound for making full-bodied, red wines,” Thornton reports. Medium- to large-sized clusters, no disease problems—resistant to bunch rot—though shot berries can be a problem on cooler sites and weaker soils, and there have been some problems with early bud stem necrosis. Some growers have planted on own-roots, though it may do better on a rootstock. Brix levels in the last three years (2008 to 2010) were 21.1, 22.8, and 18.9, respectively. Good soil and canopy management will be ­important with this variety.

Rondo (German cross of [Saperavi x Severnyi] x St. Laurent)—Thornton is impressed with the flavor profiles and with how well the wines have turned out. Good-sized bunches; larger berries may contribute to lighter style of wines. Shows some resistance to bunch rot. High sugars in 2008 at 21.5° Brix and 23° in 2009.

Zweigelt (Lemberger x St. Laurent)—Also known as Zweigeltrebe, widely planted in its native country of Austria. Thornton is very impressed with this variety that has turned out lighter-style, red wines. Variety seems to enjoy the Puget Sound climate. Large clusters are often so massive that it can be challenging to get tonnage below six tons per acre. Easy variety to manage, but need to watch for bunch rot.

Golubok—Believed to be Russian origin from the Ukraine. Has one-eighth parentage of Cabernet Sauvignon. Extremely early variety with red flesh and juice that attracts birds before you think it’s time to net. The dark, inky-black red juice could be useful in blending. Smokiness in the fruit. Susceptible to bunch rot. Probably needs 1800 growing degree-days to be able to drop acids sufficiently as they tend to stay high. Brix in 2008 was 20.2; in 2009 was 24.8.

Promising white varieties

Burmunk—Armenian origins, early ripening, fantastic aromas of peach, apricot, and tropical flavors not typically noted in western Washington varieties. Very susceptible to bunch rot. Thornton has observed small but full bunches, appears to be cold hardy. Ripens seven to ten days before Siegerrebe and is the earliest variety in his area.

Sauvignon Blanc—Clone 01 seems to have better fruit quality (Brix, acid, and such) and ripens one to two weeks earlier than clone 02. Needs bunch thinning, is susceptible to Botrytis. In warmer years, fruit has melon flavors, but grassier, traditional Sauvignon Blanc flavors in cooler years. “This is a variety I’m excited about, though I’d be cautious until we have a lot of experience growing it,” Thornton said. Early ripening rootstocks will move up ripening by ten days.

Pinot Gris—Requires at least 1900 growing degree-days, and the clonal choice is important. Rulander clones 146 and 151 have proven to be early. Variety is susceptible to bunch rot, and bunches are smaller than some varieties, but the wines being produced are promising. Pinot Gris on rootstocks has shown improvement over own-rooted Pinot Gris.

Grüner Veltliner—Been in trial for ten years, but not enough wines made yet to know its potential. Needs around 2200 growing degree-days, has nice loose bunches.

Alvarinho—Grown in northwestern Spain. Grows best under 2000 growing degree-days. First crop will be next year. Is said to continue to ripen at 50°F, which would be of high interest to Puget Sound growers.

Riesling clones—Much of the region is similar to Germany’s wine regions, and has similar growing degree-days averages as Germany’s Mosel (1831 GDD) and Geisenheim (1876 GDD) areas. Several German clones have just been planted.