The seedlings that result from my crosses are grown out in Hugo, Minnesota, located 20 miles northeast of St Paul. That is where they are initially selected for winter hardiness. The hardiness map to the right places Hugo in Zone 4B. However, that is a bit misleading. The vineyard is situated on a small glacial moraine in the middle of a wide shallow bowl. When large cold fronts move in during the winter, the bowl fills up with cold air, immersing the moraine. Turns out, this is a very cold spot. Our winter lows are more like Zone 4a or even 3b, with the average annual low temperature being 29.4 degrees F over 21 years. Eleven of those 21 years saw annual minimum temperature colder than -30F. Typically, the low temperatures in the vineyard during the winter are 5-7 degrees Fahrenheit colder than those reported in the media for St. Paul and Minneapolis. Low temps in the vineyard from the last 20 years are shown in the chart below.
The seedlings selected in Hugo for second testing are propagated and planted in test sites at vineyards and wineries around Minnesota and other cold climate states. Currently established test sites are at:
Montana State University, Corvallis, MT
New Mexico State University, Farmington, NM
Ohio State University, Wooster, Ohio
The maps at the right show the location of the Minnesota test sites (plus Fargo) on a map of USDA cold hardiness zones (upper right) and heat accumulation in DDC's (lower right).
USDA Hardiness Zones in Minnesota and TP vine test sites shown as Green dots.
Heat accumulation across Minnesota in Degree Days Celsius and location of TP vine test sites.