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Washington’s Puget Sound is not only picturesque, but it’s near major population centers.

Washington’s Puget Sound is not only picturesque, but it’s near major population centers.


Washington’s Puget Sound has long been associated with rain, and more rain—not a climate thought to be conducive to wine grape production. But a detailed look at the region’s topography, soils, growing degree-days and changing climate show good potential for grape growing in the region.

While the majority of the state’s grape production is located in the arid region on the east side of the Cascade Mountains, Puget Sound has a surprising depth of wine grape history. It was home to the state’s first bonded winery, St. Charles Winery on Stretch Island, founded by Lambert Evans, who planted grapes in 1872. More than a century later, in 1977, Gerard Bentryn established one of the region’s first commercial vineyards with vinifera-type grapes at his Bainbridge Island Vineyard and Winery, planting cool climate varieties like Madeleine Angevine, Muller Thurgau, and Madeleine Sylvaner.

The Puget Sound American Viticultural Area was approved in 1995, the fourth AVA in the state, before Red Mountain, Horse Heaven Hills, and others. Within its 7,500-square-mile boundary, about 200 acres of grapes are planted today, representing 20 vineyards. About 100 wineries are located within the AVA, with 20 of those focusing on locally grown grapes and wines. The other wineries truck grapes over from the state’s eastside to make their wines.

Puget Sound potential

Dr. Gregory Jones, research climatologist at Southern Oregon State University in Ashland, began studying the Puget Sound’s wine grape growing potential about six years ago, he said during statewide wine grape talks last winter. His study identified more than 20,000 acres suitable for varieties with annual heat units ranging from 1600 to 2300 growing degree-days (with a base temperature of 50°F from April 1 to October 31). About 12,000 of those acres had between 1900 and 2300 growing degree-days.

His involvement with the area stemmed from research he did on behalf of a group of North Olympic Peninsula growers and communities to learn if the region was suitable for wine grape production in terms of soil, climate, and topography. Computer models were used to map the region, overlaying growing degree-days, frost-free days, soil type, slope, aspect, and such, to identify areas suitable for wine grape production. He notes that a similar project is under way in eastern Washington, led by ­Washington State University’s Dr. Joan Davenport.

The Pacific Northwest climate is influenced by surface temperatures of the Pacific Ocean, and atmospheric circulation or zonal (air) flows across the region. On top of that, the climate interacts with the El Niño (or La Niña) Southern Oscillation, which lasts from three to seven years, and the Pacific Decadal Oscillation, lasting from 40 to 60 years.

Jones said, in short, it means a low risk of weather extremes for the Puget Sound, but high climate variability.

Climate trends

As part of the research, Jones looked at both 30-year Puget Sound climate averages from 1971 to 2000, averages from 2000 to 2008, and climate trends from western United States wine grape production regions (eastern Washington, Oregon, and California). He pointed out that temperatures in the 1950s and 1960s were quite cold, and even from 1971 to 2000, there were only a few areas in the Puget Sound that had adequate heat units for wine grapes.

Warming trends in more recent years have increased the nighttime temperatures and increased the number of frost-free days in Puget Sound, he said. Many areas have low risk of frost, with 180-plus days of frost-free growing. In comparing weather data from 1948 to 2008, based on five nonurban Puget Sound weather stations, Jones found the number of spring frosts had declined 12 days, and overall temperatures were getting slightly warmer. The number of ripening days from August 15 to October 15 that were above 95°F were trending upward, but not statistically significant. He explained that the warmer temperatures are primarily a reflection of higher nighttime temperatures and not significantly higher ­maximum or daytime temperatures.

Overall precipitation has not changed much in the western United States. Rain is mostly a concern for wine grapes during bloom and harvest. He found no real difference in winter precipitation in the region, but there was a trend for slightly more precipitation during bloom, though not during the ripening or harvest period.

While rain during bloom could be a concern, he said there are many isolated and protected zones with a rain shadow effect within Puget Sound. “There are some very dry zones in the area,” he said, adding that he knows of a Sequim grower who has kept records for 15 years and reports an average of 12.5 inches of rain annually.

One thing that Jones observed during the project was that the current Puget Sound AVA boundaries miss a majority of the area he identified as suitable for wine grapes. “It doesn’t include most of the area that’s suitable,” he said. Many of the warmer sites in the area—located on intermediate slopes of the foothills, isolated hillsides, up inner-sound river valleys, and over protected zones on islands—are not included in the AVA. And while Jones’s terroir modeling provides suitability insights, he noted that his research focused primarily on the North Olympic Peninsula, and needs to be done over a broader area of Puget Sound to identify the best zones for planting.

Solid potential

“I think there’s solid potential for cool-climate viticulture in this area,” Jones said, comparing the climate structure of Puget Sound to Germany’s Mosel Valley and Tasmania. “Thirty to forty years ago, I wouldn’t have said that, but today, I think a lot of potential is there for great development for the wine industry in Washington. The region benefits from its proximity to a large market, and it should capitalize on the ability to grow unique grapes with a light, crisp, and aromatic style that pairs well with the seafood of the region.”

He believes that the Puget Sound AVA should be expanded to include other areas that are climatically suitable for wine grape production. Of more than 135 AVAs in the country that Jones has looked at, most need to be redefined. “A lot of the AVAs were approved in the mid-1980s, established on frameworks that were not physically based but based on things like railroad lines, rivers and streams, and not climate, topography, and soil.”

Jones gave his talk at the annual meeting of the Washington Association of Wine Grape Growers.