Grape growing in Washington State has evolved dramatically in the last 35 years.
Attempts at viticulture by early settlers in Central Washington were mostly abandoned during prohibition. In the late 1960's WSU at Prosser, in the person of Dr. Walter Clore, took the lead at planting experimental vineyards throughout Central Washington.
The results of these experiments were noted by farmers throughout the region and they began to plant.
In 1979, growers experienced their first arctic outbreak during the winter. At minus-12 degrees Fahrenheit the buds on vines will be damaged.
Since potential for fruit is already formed in the bud any damage during the winter reduces crop load. If low temperatures continue all the buds can be killed and eventually the vine can be killed back to the ground.
Arctic outbreaks are the single biggest limiting factor in growing grapes in Central Washington. On average we experience severe cold-air outbreaks two out of every ten years.
One of the most effective ways to deal with this is to carefully choose the vineyard site. Cold air is heavy, so you want a site with no gullies or trees to trap the cold air.
This is effective not only for winter cold but also protects against spring and fall frosts. Thus most vineyards are on hills.
Another option is to be close to a body of water which does not freeze such as Lake Chelan or the Columbia River.
Here at White Heron, we are on a relatively steep slope above the Columbia River and I can assure you it did not happen by accident.
During the cold winter of '95-'96 we experienced temperatures of minus-13 on our hillside and had no damage in our vineyard.
During that same period the black sands region of the Quincy Basin, where cold air drains from the whole basin, temperatures got as low as minus-28. Thus site selection is extremely important.
In the fall of 2010, temperatures plunged to minus-6 in many areas of the state.
The true extent of the damage is still being assessed as of this writing. Once again, we experienced no damage here.
Wenatchee Valley Vintners planted their vineyard in a gully below Pangborn Field and experienced fairly severe damage during a mild winter whereupon they abandoned their vineyard.
Another method for combating cold is varietal selection.
Certain varieties, such as Merlot and Grenache, are far more sensitive to low winter temperatures than varieties such as Riesling.
In addition, hybrids - genetic crosses between European and American grapes - are very winter-hardy. Concords can be planted just about anywhere with no concerns.
It is for this reason that when you travel in the Midwest the most common grapes planted are the hybrids, capable of dealing with severe winter temperatures.
In the last twenty years, we have begun to utilize the tools of irrigation to stress our vines. This tends to make for better grapes but it also stresses the plant and causes it to harden off - in other words turn its branches brown in preparation for dormancy.
This helps to prepare the plant for winter and subzero temperatures.
Concern for winter damage explains why most Washington vineyards wait until March to prune their vineyards. These vineyardists are waiting to assess potential damage from the winter.
If there is damage, they can prune longer, leaving more buds in an attempt to have a normal crop.
As in all areas of farming, nature has a heavy role in the viticultural life.