Temperatures That Kill Concord Grape Vines

Concord Basics

• Concord is a slip-skin grape, meaning that the interior slips easily from the skin. It also has seeds. Table grapes usually have thin skins and no seeds. Concord grapes are grown commercially for juice and for making jams and jellies but are not preferred for wine because of their distinctive “foxy” or “grapey” taste that is difficult to define. The growing season is the time between the last spring frost to the first fall frost. Depending on the amount of sun in your area, concord grapes may not ripen for 155 or even 160 days.

Commercial Growing Climates

• Concord grapes are grown commercially in the Finger Lakes region of New York, USDA Zone 5a and the Yakima Valley, Wash., USDA Zone 6b that has winter temperatures of minus 5 to zero degrees Fahrenheit. They are also grown on the southern shores of Lake Erie and Lake Ontario where harsh winter temperatures are moderated by the water. The growing zones there are USDA 5B, minus 10 to minus 15 degrees Fahrenheit and USDA 6A, minus 15 to minus 10 degrees Fahrenheit. Temperatures below these can kill the vines.

Similar Labrusca Cultivars

• Newly developed cultivars of Vitis labrusca have many of the same properties as concord grapes but can survive temperatures down to minus 20 degrees and ripen in far less time than normal concord grapes. Northern New England growers plant Vitis labrusca Fredonia, a large blue-black grape that grows in large, compact clusters and matures 20 to 30 days before Concord. Fredonia will grow in USDA Zone 4b that has winter temperatures from minus 20 to minus 25 degrees Fahrenheit. Vitis labrusca Bluebell matures earlier than Fredonia and will survive winters of USDA Zone 4a with temperature of minus 25 to minus 30 degrees Fahrenheit. The University of Minnesota has developed Vitis labrusca Reliance and Edelweis grapes that are good for both eating and making wine and will survive USDA Zone 4a.

Extending Growing Season

• Growers in New England mulch their grapes heavily in the winter to hold heat around the roots. They remove the mulch in the early spring to let the sun warm the soil around the roots, a practice that extends the growing season one week. They put the mulch back in place in early June to discourage weeds.