by Judith Reith-Rozelle, Stonehoe Consulting, Spring Green, WI
Seedless table grapes picked fresh from the vine have that “picked fresh” from the tree taste that we all love when eating a true “ripened on the tree” peach. Wisconsin’s soil and climate produce grapes that have unique flavors beyond any supermarket grape ever purchased, and they retain the healthy nutrients found in fruits fresh from the garden. The California Grape Commission blog documents the following health value of grapes: “Grapes of all colors—red, green, and black—are a natural source of beneficial components called polyphenols, which are also antioxidants.”
Now home gardeners and vineyard owners can grow seedless table grapes in Wisconsin with careful management and selection of varieties for the zones in each area. Breeding programs across the country are releasing new winter-hardy selections, and several older hardy Elmer Swenson varieties are once again being planted.
The major limiting factors in producing seedless table grapes in any temperate climate is the ability of the vines to survive the freezing temperatures of northern regions, late spring frost, and fluctuating rainfall. The cropping loads, disease infections, and drought also impact cold hardiness. Each of these factors stresses the plants and decreases the vines’ ability to develop strong overwintering capacities.
The length of the growing season or ripening period also dictates what cultivars can be grown in regions where the frost-free days may be fewer than 150 days. The growing season is determined by the dates of the first and last frost of any one year.
Grapes grown in cold climates must be grown using methods other than those in warmer climates. The vines must be allowed to develop deep, healthy root systems before fruit production begins. Trellising to allow for strong trunk development increases the winter viability of vines. Fruit clusters must be removed the first two years. A few clusters may be left on the vines the third year and the two-thirds fruit load during the fourth year. Four years of good, strong growth is mandatory before a full fruit load is allowed to remain on the vine.
The fruit allowed to develop on the vines the third and fourth year will allow a grower/gardener to evaluate the quality and harvest time of the fruit produced. In the trials at the research stations three varieties were removed from the trials the third year. Either the fruit was unpalatable or ripened too late for Wisconsin’s growing season.
Seedless table grapes have been grown at the West Madison, Peninsular, and Spooner University of Wisconsin agricultural research stations for over seven years. At least fifteen varieties have been trialed at West Madison and Peninsular research stations. Fewer varieties have been trialed at the Spooner station. Spooner lies in Zone 3b, so fewer of the varieties survive the minus 30 degree temperatures. Interesting aside; Phil Holmen, superintendent of the station, reported on January 10 that Spooner area had already experienced thirteen days of minus 20 degrees this winter. There may be fewer varieties that survive this year at all three stations. Lower temperatures, for longer periods of time have already been experienced at all research sites than in the past seven years.
Several new varieties were planted in 2010 and have grown well and produced a limited number of really beautiful, tasty fruit in the third year. The summer of 2014 will be the true test for fruit flavor and production levels.
The twelve varieties of seedless table grapes have survived seven Wisconsin winters and the four newer have survived three winters. The lowest temperatures at the West Madison Station reached minus 18 to minus 19.5 degrees.
Red, blue,and green grapes are all part of the collection that have survived. The green and red grapes have been a true survival surprise and are some of the most flavorful grapes on the market.
The four varieties of red grapes include: Canadice, Reliance, Somerset Seedless, and Vanessa. The ripening sequence begins in early to mid-August with Somerset Seedless, followed by Vanessa, and Canadice, then Reliance rounds up the harvest ripening in early to mid-September. Of the four, Reliance is the hardiest, but it is harder to grow and does not ripen as uniformly as Canadice. Canadice and Somerset Seedless are the most flavorful: spicy and sweet. The colors of each variety are so beautiful: Reliance is a softer rose/green, and the remaining three are deep, rose colored.
The four varieties of white/green grapes include: Himrod, Interlaken, Lakemont, and Marquis. These grapes begin to ripen a little later than the reds listed above. Their flavors are very spicy and complex, and each is grape is very juicy. What a treat to harvest fresh green grapes right before breakfast or lunch.
Three blues, Mars, Trollhaugen, and Venus, ripen beginning in mid-August and finish in mid-September. Trollhaugen is first to ripen, followed by Venus and then Mars. Each has a very unique taste and texture. Venus has a very surprising burst of flavor a bit like pink grapefruit; Trollhaugen is sweet and spicy. Mars has more of the Concord taste.
The four new varieties planted in 2010 are: Montreal Blue, Suffolk Red, Thomcord (blue), and Jupiter (blue). Look for more information on these four in 2014.
Research shows that eating as little as 1¼ cup of grapes per day may reduce the risk factors for coronary heart disease. Plan your backyard garden grape arbor now and reap health benefits from the work for thirty plus years.
Now retired as a leader of the UW’s West Madison Agricultural Research Station, Judith Reith-Rozelle did research into the viability of cold-hardy table and wine grapes. She now serves as a private consultant to growers throughout the Midwest.