Loudoun County winemaker Doug Fabbioli examines frost-damaged merlot grapevines three years ago, when a late cold snap destroyed most of his crop. A freeze last month also caused damage, but Fabbioli estimates he’ll be able to harvest about 80 percent of a normal crop. (Tracy A. Woodward/WASHINGTON POST)
Columnist, Food

We may be schvitzing now, but remember a few weeks ago when we moved our plants inside and heated our windshields in the middle of May? That Arctic cold snap and heavy frost on the morning of May 14 hit hard along the Blue Ridge, causing considerable damage to many Virginia and Maryland vineyards. Others escaped harm due to local temperature variations, geography or hard work by vintners.

Grapevines are especially susceptible to frost damage after the buds emerge and the shoots begin to stretch and form grape clusters. When the temperature plummets, ice can form in the fragile buds, shoots and leaves, bursting the cells and effectively killing them. The vines may grow secondary shoots and still produce a crop, but those grapes tend to be of lesser quality because they start later and have a shorter growing season.

Vineyards planted on steep slopes have the advantage of “air drainage,” as cold air sinks and is trapped low to the ground by a warmer inversion layer of air. Vines higher on the slopes are protected by that temperature variation. At RdV Vineyards in Delaplane, vintner Rutger de Vink reported no frost damage, while at Glen Manor Vineyards near Front Royal, Va., Jeff White noted minor effects on his lower vineyards but no problems on steeper plantings. 

Barboursville Vineyards, north of Charlottesville, took extreme measures to ward off frost. Crews lighted 300 fire pots to warm air around the vines while running 12 wind machines and hovering a helicopter over the vineyards for several hours to move the air around, winemaker and general manager Luca Paschina said. 

At Boxwood Winery near Middleburg, vineyard manager Andrew Smuts and winemaker Johnston Mooredrove “frost dragons” — large propane burners with fans hitched to the back of tractors — through the vine rows to warm the air. They were able to cover the 20-acre vineyard every 15 minutes, Moore said. As a result, Boxwood experienced no significant frost damage.

Efforts at Fabbioli Cellars, farther north in Loudoun County, were less successful. Owner Doug Fabbioli invested in a frost protection system after suffering significant damage in 2010 and used it effectively six times last year. The system pumps cold air up and draws warm air down to protect the vines. However, “that night the air mass was so big that there was no warm air to pull from,” Fabbioli said. He estimated he lost about 50 percent of the buds that had formed, with merlot and carmenere at the lower parts of his vineyard hit especially hard. 

“The vines are recovering pretty well,” Fabbioli said 10 days after the frost. “I’ve been frosted before, so I know what it feels like.” He estimated that he could still harvest about 80 percent of a normal crop, since some vines had not yet budded at the time of the frost and were unaffected.

Across the Potomac in Dickerson, Sugarloaf Mountain Vineyard “got whacked,” said Michael McGarry, an owner and manager. Vineyard crews had sprayed potassium, which can protect vines for a half-hour down to 28 degrees. It wasn’t enough. The temperature fell to 26 degrees and stayed there for several hours, McGarry said. 

“All our varieties were affected, but the late bloomers — cabernet sauvignon and merlot — really took a beating,” McGarry said, estimating that Sugarloaf might get only half the normal crop of those two varieties.

Elsewhere in Maryland, vineyards in Allegheny, Washington and Frederick counties reported frost damage, often extensive, while those on the Eastern Shore and southern Maryland were unscathed, said Joseph Fiola, viticulturist with the University of Maryland. 

Could there be a silver lining in these frosts? Local vintners weathered the “Easter Massacre” of 2007 and the Mother’s Day frost of 2010, yet both of those years turned out to be excellent vintages locally. 

The quality of 2013 won’t be determined until harvest. Although the danger of frost may now have passed, other weather hazards lay ahead: most immediately, the possibility that a sudden heat spike might “shatter” the delicate flowers before they can successfully set fruit.

“This cool spring, where we are 50 degrees one day and 90 the next, is concerning because we don’t have the consistent weather we’d like. But every year is different,” Fabbioli said. “That’s what makes it exciting here.”

McIntyre blogs at dmwineline.com. On Twitter: @dmwine.