Northwest Grapegrowers Mull Damage

Temperatures dip below zero in Washington and Oregon wine regions

by Peter Mitham
Pickers are bundled up to pick frozen grapes at Summerhill Pyramid Winery in Kelowna, B.C.
Ashland, Ore.—It's been a year of extreme weather for the Northwest. Record-melting heat in July was followed by September rains that washed away century-old records. Now, a cold snap has growers-particularly those in Oregon-worried that some of the region's newest vineyards may have suffered significant damage.

This past weekend saw temperatures dip to -2° F in Ephrata, Wash., according to the National Weather Service, breaking the previous record set in 1972.

Hermiston, Ore., registered a temperature of -8° F, while temperatures in Ashland, Ore., bottomed out at -17° F and Klamath Falls registered a low of -20° F, a degree lower than the previous record set in 1972.

Those temperatures have sparked concern among those familiar with local vineyards, especially the volume of new plantings in Southern Oregon and the Willamette Valley.

“Based on my understanding, the damage could be similar with that from 1996, when the industry was really hurt,” Gabriel Balint, an instructor and extension horticulturist in wine grape production at Oregon State University told Wines & Vines earlier this week. “I am concerned that the vine cold acclimation was really short, and the vines did not reached their maximum hardness.”

One grower who contacted Balint expressed concern that a year-old block might have to be completely replanted, but Balint cautioned that a coordinated evaluation of vineyards hasn't been undertaken.

“Hopefully, the vascular tissue was not affected too much and the vines can recover,” he said.

Experience has shown Northwest vineyards to be resilient.

Bouncing back
Recent cold snaps that were forecast to have devastating consequences often had a smaller impact than expected.

An early frost in November 2010 led to fears of some vineyards in the Horse Heaven Hills being totally lost. Other vineyards were unscathed (as recent research by Dr. Kevin Pogue of Whitman College indicates, topography plays a significant role in how pools of cold air render some vineyards more vulnerable than others (see “Topography and Temperature”). 

Northwest Farm Credit Services forecast that upwards of 20% of Washington state vineyards could see “significant damage” from the 2010 cold snap, though it deferred a definitive statement until bud break in spring 2011. But the harvest in 2011 was down just 11% from the previous year-from 160,000 tons to 142,000 tons-a notable yet relatively minor hit to production. The following year, in 2012, production rebounded to a record 188,000 tons.

Similarly, a hard frost in October 2008 cut the harvest short with fruit still on the vine. The vines hadn't yet entered senescence, and then, when winter finally did arrive, an Arctic front in late December dumped snow and extreme low temperatures on the Northwest. Temperatures in the Okanagan on several occasions dipped below -4° F, with one block near Oliver recording -16.2° F).

This prompted speculation that some vineyards would see losses of at least 25%.

When all was said and done, however, losses in British Columbia's south Okanagan were estimated at approximately 20%. Government estimates of harvested tonnages were up that year in both British Columbia and Washington state.

This year Kevin Corliss, vineyard operations director for at Ste. Michelle Wine Estates, anticipates little or no damage from the cold seen to date. Viticulture staff has yet to detect damage, with the most vulnerable vines being plants still in tubes.

“The vines are quite hardy at this point of the winter,” he told Wines & Vines. “There may be localized damage in small cold pockets.…We'll continue to evaluate.”

Ice wine harvest
The good news is that colder temperatures-even before the latest blast of Arctic air-have let growers across the Northwest proceed with an early harvest of ice wine grapes.

Producing the coveted dessert wine requires air temperatures of at least -8 degrees C (17.6° F), which allows a sustained freeze of grapes remaining on the vine. The grapes are then crushed while still frozen, yielding juice of at least 35° Brix.

This year growers in British Columbia began harvesting grapes for ice wine Nov. 20, as temperatures dipped to 14° F), while Chateau Ste. Michelle harvested its first ice wine grapes since 2008-the seventh in its history.

British Columbia saw 29 wineries register their interest in producing ice wine this year, with the harvest potentially totaling 1,000 tons-the largest intended harvest ever.

This year's harvest in British Columbia was the third-earliest on record, ranking after harvests Nov. 5, 2003, and Nov. 19, 2011.

Looking ahead, Greg Jones of the Department of Environmental Studies at Southern Oregon University in Ashland believes growers are in for a grab-bag of weather this winter.

“We are likely to see a little bit of everything this winter, as evidenced already by the record-setting wet September followed immediately by a long spell of dry weather in October, followed by the record cold in early December,” Jones said in a report this week.

Posted on 12.12.2013 - 14:01:27 PST
Not sure where the -17F in Ashland came from but it didn't get anywhere near that cold, maybe -1. We have 11 vineyard sites across the Rogue Valley and the coldest temperature we recorded was 1. We will be scouting for damage in the coming weeks/days but I think the concerns at this point are a bit of a knee-jerk reaction.
Daniel Sweeney