Growing grapes that can be turned into tasty wine always has been a formidable challenge in Minnesota. But this year brought a truly unexpected setback:

It never got cold enough for vintners to make ice wine. This week's cold snap was a month too late.

"You should be able to produce an ice wine in Minnesota every year, for crying out loud," said John Mahoney, owner of the Cannon River Winery in Cannon Falls.

Not this winter, although Mahoney has devised a "workaround" (more on that later).

To make traditional ice wine, growers let grapes stay on the vines well past the normal harvest, until they freeze. The water in the grapes becomes ice crystals, which are pressed out during the crushing process, leaving only highly concentrated, very sweet juice (the Brix level, a sugar measure, rockets from 22 to the high 30s, Mahoney said).

Because grapes are about 80 percent water, the yield for ice wine is very low; that's why it's so expensive, usually $30 and up. Ice wine is most popular in Germany and Canada, and obviously suited for Minnesota. The motto at the state's oldest winery, Alexis Bailly, is "where the grapes can suffer."

They didn't suffer enough this season, despite an extremely promising start.

"We usually like to pick the last week of November or the first two weeks of December," said Kyle Peterson, whose family owns WineHaven in Chisago City. "The best conditions for ice wine are a long, late fall and not much frost till mid-October, then an Indian summer -- and then, boom. really cold. It was setting up real well, and then winter never hit. At Christmas, my family said, 'Well, no ice wine this year.'''

WineHaven makes ice wine every other year -- "it's hard on the vines," Peterson said -- and follows the German model of picking after the temperature has been minus-7 Celsius (about 19 degrees Fahrenheit) for a prolonged period. "I never thought we wouldn't get in the teens by mid-December," Peterson said.

A safety net

Mahoney also didn't get any December yield from his vines, but there will be a 2011 Cannon River Ice Wine. That's because he recently switched to "two parallel tracks" in producing the sweet stuff.

Many of Cannon River's St. Pepin grapes remain on the vines, but the winery also brings in a lot of late-harvest grapes in late October and freezes them indoors, then "presses off that syrupy juice," Mahoney said. Not only does that ensure that Cannon River's Winter Carnival Ice Wine will be available at Rice Park next year (this month's carnival features the 2010), but Mahoney said his indoor freezers do a better job than Mother Nature.

"We see time and time again that the wines created with grapes that have been brought inside and frozen are much better than the ones from outside," Mahoney said.

Meanwhile, all the Petersons can do is wait till next year. "I grew up with agriculture," Peterson said, "and we know there are risks. But to be completely honest, I never thought our risk would be Minnesota not getting cold enough."

Bill Ward • 612-673-7643