The Geography of Northwest Wine
For a deeper appreciation of what distinguishes the Pacific Northwest as a winegrowing region, it is important to understand the interplay between three vital wine variables: place, plant, and people. I like to think of it as a formal: Great Wine = (Place + Plant) x People. Understanding the Northwest (or any wine region, for that matter), means understanding the interplay between these elements.
The place to start is with . . . the place. The Pacific Northwest, despite its great size and geologic variation, shares some key factors that unite the region’s wine growing areas into one vast contiguous wine country.
The Significance of Latitude
In the northern hemisphere, Vitis vinifera grows well within a band between latitude 32°N and 51°N. Within this range, the climate offers sufficient overall warmth for wine grapes to ripen properly. Though not every location within this band is suitable for wine grapes, grape growing is broadly feasible. At higher latitudes outside this range the climate is too cold to ripen grapes reliably, and at lower latitudes the climate is too warm and humid.
Importantly, the Pacific Northwest’s wine countries are all within the upper 10º of wine growing latitude in the northern hemisphere. The most northerly Northwest wineries lie a little above 50°N latitude—equivalent to the northernmost of Europe’s ancient wine regions—while the southern boundary of Northwest wine countries is at 42°N.
When the modern era’s early winegrowers looked at a map, they were impressed by the Northwest’s latitudinal similarity to the great French regions of Burgundy and Bordeaux. Surely that was a portent of good viticultural potential, they thought. And yet, the most successful wine region in North America was certainly California, located at relatively low latitudes, from Mendocino in the north at about 39°N to Santa Barbara in the south at about 34°N. Were these latitudes better for wine growing?
The Northwest’s pioneers thought not. They saw the region’s location at the northern edge of viticultural viability as offering important winegrowing advantages. In particular, the northerly location delivers two critical benefits: more sunlight and more coolness.
Vineyards in the Northwest receive distinctly more sunlight hours per day during the growing season than vineyards further south. Oregon’s wine countries receive a little over an hour more sunlight than California’s key wine regions, while Washington’s vineyards get about two hours more sunlight than Napa Valley. And Sumac Ridge, a winery in British Columbia, claims its Black Sage Vineyard receives more sunlight hours than any other vineyard in North America, and the most sunlight intensity of any vineyard in the world.
This extra sunlight means that potentially more grape varieties can be optimally ripened in Northwest wine countries. At any point in the growing season, Northwest grapevines receive more solar energy for photosynthesis than the same plant would at the same point in the season at more southerly latitudes. In cooler Northwest appellations the extra sunlight helps grapes ripen well even when average temperatures are relatively low. In warmer reaches, the extra sunlight gives growers flexibility on when to harvest for optimal ripening and balance.
The northern latitude also means some areas are viticulturally cool—such as the Willamette Valley and the western portions of British Columbia—with growing conditions well-suited for cool-adapted grapes. The cooler growing temperatures combined with the extra sunlight make for optimal conditions for early-ripening grapes. These varieties in cool areas do not rush to ripeness because of abundant heat, but rather mature at an even and natural pace, generally achieving more balanced ripening and expressive varietal character.
The latitude also delivers well-defined seasons and cold winters, two under-appreciated viticultural advantages. Here the transition from growing to senescence is distinct and usually rapid as the seasons are clearly delineated—grapevines easily reach the full dormancy that can be difficult to achieve in the milder winters of lower latitudes.
Finally, the northerly latitude helps grapes naturally retain acidity, a vital component of balance, freshness, and verve in wines. In the cooler parts of the region lower average daytime temperatures increases the retention of acidity as the grapes ripen (warmer temperatures increase the pant’s respiration). Even in the warmest parts of the region, very cool nighttime temperatures (creating a large diurnal swing) enables warm-climate grapes to keep their acid levels naturally higher than in southern latitudes, even though daytime temperatures can be very warm. This gives the wines a fresh-fruitiness that can be a notable signature of Northwest wines.
The Effects of Ocean and Mountains
The two geographic features most salient to determining the viticulture of the Northwest are the Pacific Ocean and the mountain ranges of the coast and Cascades. The sway in which landforms block and channel the eastward movement of marine air in the Northwest is one of the prime determinants of what and where wine grapes grapes grow well.
Prevailing westerly winds constantly push relatively cool and moisture-riuch marine air toward the coasts of Oregon, Washington, and British Columbia. As the air moves eastward, it meets coast mountains that inhibit its movement landward. In Oregon it first encounter the Coast Range, in Washington it hits the Olympic Mountains, and in British Columbia it meets the Vancouver Island Ranges.
These mountains act as a rain barrier, a critical geographic theme in the Northwest. The lower land on the lee side of these mountains is in the rain shadow and the weather here is correspondingly drier and warmer than the ocean air. The interior valleys on the eastern slopes of the coast mountains form one important class of Northwest wine country: the marine-influenced cool climate regions. AMong these are Oregon’s Willamette Valley AVA (and its child AVAs), Washington’s Puget Sound AVA, and the Vancouver Island, Gulf Island, and Fraser Valley DVAs of British Columbia.
Farther inland, a second, greater rain barrier is formed by the majestic Cascade Range, with mountains between 5000 and 14000-ft. in elevation. Extending from southern British Columbia down to southern Oregon these ranges prevent nearly all the marine air from penetrating eastward. Storms wring out all their moisture on the west side of the mountains, leaving the lands to the east, literally, high and dry. This is where the Northwest’s second kind of wine growing area is found: the continental-influenced, warm-climate wine countries. These include some of the most productive grape growing regions in the Northwest: Washington’s Columbia Valley and Walla Walla Valley AVAs, British Columbia’s Okanagan and Smilimkameen Valley DVAs, and to a lesser degree, all of Idaho’s Snake River Valley AVA.
The Unifying Columbia River Waterhsed
With the Northwest’s geography creating such starkly different types of wine countries, it might seem a stretch to think of the region as a single unified wine region with a common identity—but it is. The unifying factor is the 258,000-square mile watershed of the mighty Columbia River. Beginning at Columbia Lake in British Columbia, the Columbia River flows 1270 miles toward the ocean. About 85% of the Pacific Northwest’s vineyards—and over 90% of its total wine production—are located along the hillsides, valleys, and slopes of the tributary rivers and basins that drain into the Columbia River. The only Northwest wine countries that aren’t located within this watershed are relatively small (in terms of production volume) Southern Oregon and Puget Sound AVAs, and the Vancouver Island, Gulf Islands, and Fraser Valley DVAs.
Massive lava flows
The ancient creation of this watershed was dramatic by any measure, and shaped the Northwest’s best-known wine countries. Approximately 15 million years ago, huge fissures many miles long opened in the earth’s surface in what is now eastern Washington and Oregon, emitting massive flows of lava that swept across the land. These shield volcanoes continuously inundated the land with oozing liquid rock for millions of years, flowing into what is now central Washington, southeastward along the Snake River toward Boise, westward through what is now the Columbia Gorge, and down into the Willamette Valley. Eventually these basaltic floods covered about 65,000 square miles to a depth of 8,000-ft. and now forms the bedrock underlying most of the Northwest’s vineyards.
The sheer weight of this immense basaltic mass caused the entire area to fold and warp as it sank little by little into the crust. Over millennia, the area now called the Columbia Basin tipped gently to the south and dropped in elevation. It is into this vast catch basin that much of the Columbia River watershed flows today.
Mammoth Missoula Floods
But that is not the end of the relevant geologic story. During the last Ice Age, roughly 15,000 years ago, part of the Cordilleran ice sheet, a virtula ocean of frozen water that covered much of Canadian North America, crept into northern Washington and Idaho. One arm of the ice sheet created an almost unbelievably massive ice dam along the Clark Fork River. Geologists estimate it was 30 miles wide and 2,000-ft. high, holding back 500 cubic miles of water in what is called Glacial Lake Missoula.
At some point, the dam failed catastrophically. With instantaneous and monstrous violence, the largest floodwaters ever experienced in earths geologic history exploded westward throughout the columbia River drainage. The scale is difficult to imagine. A wall of water 2000-ft high with a volume equal to the flow of all the rivers of the world—times ten!— rushing at 65 mph swept through hundreds of miles of territory, sweeping with it nearly everything, including massive boulders the size of houses. And it didn’t just happen once, it happened perhaps more than a dozen times.
Each of these so-called Missoula Floods scoured the land down to the basalt bedrock, obliterating ancient soils (the effects can be dramatically seen in eastern Washington’s geology . . . just check it out on Google Earth: view the area north of Benton City, Washington). But the floods also left behind gargantuan deposits of gravels, rocks, and boulders as each flood swirled, slowed, and receded. In some places deposited gravel bars are miles long and hundreds of feet deep. These are the substrates upon which the topsoils of today’s vineyards later formed, from the Columbia Valley in the north, to the Snake River Valley in the east and the Willamette Valley in the south.