It was about a decade ago when the growth of wineries in the United States spread to all 50 states. Even so, not every state grew winegrapes. That's because weather conditions in some areas are so extreme that it's economically unfeasible. Some places get so cold that vines suffer from winter kill. Other regions have such humidity that molds and other vineyard maladies cause rot and make growing grapes all but unprofitable.

So it was with a fair bit of skepticism that I accepted an invitation to judge wines at the third International Cold Climate Wine Competition at the University of Minnesota last week. And what I learned over the course of just two days was a revelation.

Border to border, the West Coast is known as wine heaven, blessed with temperate climates that permit fine wines to be made are far north as the Okanagan Valley of Canada and to the south in the Guadalupe Valley of Mexico.

But most Americans are unaware of many of the other exciting regions where wine grows. In the past I've seen the excitement of emerging wine regions in New York in the late 1970s, and less than a decade later in Virginia and Missouri.

A recent trip to Colorado wine country was a dramatic experience and excellent wines are today being made in Michigan, Ohio, Missouri, Texas, New Mexico and at least a dozen other states.

Most of these regions faced daunting viticultural problems that forced growers to adapt. Some have done it by outsmarting Mother Nature, and none with a more radical plan than here in the far north.

And the reasons are obvious. The brutally cold winters here would kill the more sensitive French grapevines that go by names we all know well — Chardonnay, Cabernet Sauvignon, Zinfandel, etc.

But even more winter-hardy French-American crosses such as Baco Noir, Marechal Foch, Seyval Blanc and Vidal can be affected by the cold here. So Minnesota and other really cold growing regions have done it by breeding their own grape varieties, such as Edelweiss, Frontenac, La Crescent, Marquette and a host of other grapes bred specifically to survive through the harshest winters.

Most of the new grapes were developed here at the university, and some are so new that few people outside this area have ever tasted them.

But you can imagine why such vines were necessary when even the supposedly winter-hardy French-American hybrid grapes (which typically withstand cold weather) often died in the Minnesota cold.

One method for protecting vines from below-zero weather was to push them to the ground, lying down, after the harvest and then to cover them in straw. When spring melted the snows, the vines were listed upright. Sometimes even that didn't work.

That's why grapes like the red Frontenac were developed. According to the university website, "This vine has borne a full crop after temperatures as low as -33? when properly cared for."

So how are the wines? Well, that somewhat depends on the taster's ability to understand new and occasionally very different aromatics and tastes. For one thing, most of the new grapes are picked with a lot of acidity, so even dry wines often have some sugar left in them. And many reds would be undrinkable without a bit of sugar.

Are the wines successful? So far, so good. In 2001, the state had nine wineries. Today there are 40, and almost all of them are using locally developed grapes. And the wines are selling out the door at tasting rooms.

The local wines have yet to catch on, however, in local retail stores, and part of the problem may well be that consumers best understand such wines when they can get a chance to taste them before buying, to determine how much sugar is in them. That's why tasting room sales are brisk.

Fortunately for the new grapes, they have many other supporters, all wineries in cold climes. Wineries in Wisconsin, Rhode Island, Maine, South Dakota and all along the northern border with Canada are using the new varieties.

The more exposure they get, the more the public will understand them.

<CF103>Wine of the Week: </CF>2010 Mirassou Riesling, California ($12) — Attractive floral/apple aroma with a bit of spritz and some residual sugar. The wine is best with fruit salads or spiced Asian foods.

[END_CREDIT_0]Sonoma County resident Dan Berger publishes "Vintage Experiences," a weekly wine newsletter. Write to him at winenut@gmail.com.