Hugo, Minn.—It’s common knowledge that it gets cold—very cold—in Minnesota every year, and not just during winters with unusual polar vortexes. Yet wild grapes such as Vitis riparia survive temperatures that drop to -30° F and lower without suffering from dead buds and split trunks. The challenge to growers has been to breed new varieties with resistance to extreme cold as well as the ability to produce grapes that can be made into high-quality wines.

Tom Plocher, a grape breeder living northeast of Minnesota’s Twin Cities recently named two red varieties, Crimson Pearl and Verona. While both are cold hardy and have excellent wine potential, they have different attributes in the vineyard and the winery. The benchmark variety for the two grapes is Petite Pearl, a sister grape of Crimson Pearl, which Plocher named in 2009. Petite Pearl and Crimson Pearl were the results of crosses in 1996 between MN 1094 and ES 4-7-26. MN 1094 is a University of Minnesota hybrid with a genetic background of vinifera, riparia and other species. Winter temperatures in 1993 and 1996 dropped to -40° F, and most hybrid grapevines died, except for MN 1094. ES 4-7-26 is a cross Elmer Swenson selected from seedlings of his variety called St. Croix.

Crimson Pearl is noted for its early wood ripening and great winter hardiness. According to Plocher, it is “the most rugged vine from my work; very reliable in Zone 4b and has performed well in the Zone 4a test sites as well.” The vines have a relatively late bud break and a neat growth habit with moderate vigor. Like its sister grape, Crimson Pearl has good disease resistance and little rot. In contrast to Petite Pearl, it ripens 10 days earlier, the grapes have less tannin in the skins, and the juice is not as dark.

Typical harvest parameters are 22-23° Brix, pH between 3.4 and 3.8, and total acidity of less than 0.8 grams per liter. The best wines so far were a fruity, raspberry-like, cold soak rosé; a saignée rosé with tropical fruit notes, and a soft, fruity dry red. All had complex aromas of temperate climate fruits, and there were no hybrid or native flavors in the wine.

Originally known as T.P. 2-1-17, the name Crimson Pearl was the overwhelming choice of wine consumers who participated in a Facebook poll conducted by Carlos Creek Winery of Alexandria, Minn. Plocher told Wines & Vines, “We had 800-plus votes on Facebook. Using customers initially this way is great—the name will resound with them, and we know we have the customer appeal down. It was a really successful way to handle the initial marketing for the grape.”

Verona, formerly known as T.P. 1-1-34, is a 1997 cross between Troubador (a cross by David Macgregor of Riparia 89 x St Croix) and E.S. 5-4-16, one of Swenson’s unnamed varieties. While the vines have good winter hardiness, some injury has occurred during the worst winters. One advantage is Verona’s late bud break in the spring, and the fact that it has good production on secondary buds.

Verona’s leaves have some resistance to fall frost, which allows the fruit to hang and ripen later into the fall, with harvest often taking place 10 days after Petite Pearl. Grape parameters are 22-24°Brix, pH of 3.25, and total acidity of less than 1.0 gram per liter. In tests at North Dakota State University in 2012, ripe berries from Verona vines ranked No. 1 in tannin content out of 34 skin samples from northern grape varieties, with a good ratio of tannin/total polyphenols.

In naming Verona, Plocher considered using a poll similar to the one that came up with the name for Crimson Pearl. None of the names suggested, however, seemed to work well with the grape, so Plocher took wine made from T.P. 1-1-34 to his friend, Tony Nasello, who with his wife Sarah owned Sarello’s restaurant in Moorhead, Minn. Nasello grew up in the Veneto region in northeastern Italy, and the raspberry aromas and overall balance and style of Plocher’s wine reminded him of wines he had tasted in Verona. With that suggestion, Plocher found the name for his variety.

The dry red wine made from Verona grapes is deeply colored and has abundant soft tannins in the mid-mouth and finish. According to Plocher, the wine has a “great balance between acid, tannin and alcohol. The aroma is complex; characteristic raspberry aroma is dominant, changing to blackberry as it ages in the bottle.” There are dark chocolate flavors along with raspberry, with an excellent balance and finish, all in a “style that is a bit reminiscent of a Tuscan red wine.”

Both Crimson Pearl and Verona are in the second year of virus testing at Foundation Plant Services at the University of California, Davis, and Plocher expects to have certification for the varieties in 2016. He also is applying to TTB for name approval of both grapes.

The pioneer grape breeder for cold-climate varieties was Elmer Swenson, a farmer in Wisconsin who began to breed grapes in 1943. Swenson joined the staff of the University of Minnesota’s Horticultural Research Center in 1969. During a 60-year career breeding grapevines he named 15 varieties and produced dozens more that are valuable in breeding programs. Swenson was Plocher’s mentor in breeding grapes, and when Swenson became elderly, Plocher helped him maintain his vineyard.

Plocher’s next goal is to try to solve the problem of early bud break. He noted, “The climate change in Minnesota seems to be that we’re getting more years with high and low temperatures at odd times of the year.” In 2015 temperatures in April did not get down to 0° F or below, but in two of the four years prior to that, temperatures were in the 70°s in the third week of March for six or seven days and then dropped to 0° F in early April.