Screening Grapevine Cultivars for Adaptability to Soil and Climatic Conditions in Wyoming

Grape production in Wyoming evinces strong interest from producers exploring new crops in addition to traditional crops, as well as homeowners with backyard plantings. Low winter temperatures, late spring frosts, and a short growing season limit the cultivation of traditional cultivars in Wyoming. With the development of new cold-hardy grape cultivars, the scope for grapevine production in colder regions of the United States, including Wyoming, is rapidly expanding. The goal of the project is to identify promising grapevine cultivars for Wyoming, thus overcoming obstacles to initial vineyard establishment, resulting in increased production and early returns. Ten cold-hardy grapevine cultivars that have been developed from interspecific hybridization of Vitis vinifera with American grape species (Vitis labrusca and Vitis riparia) were planted at Sheridan and Powell, WY. Vines were planted at 10 feet x 5 feet spacing in 30-cm deep holes that were filled with compost and supplemented with 50 g 19:6:12 slow-release fertilizer. A drip irrigation system was installed to provide irrigation during periods of extreme drought. Vineyard irrigation was terminated at the end of September to initiate grapevine acclimation for winter conditions. Budbreak and vine survival rates were recorded in the spring to estimate vine winter damage and cold-hardiness of various cultivars. Preliminary results indicated significant variations among grapevine cultivars in timing of budbreak and vine survival rates at the two locations. Budbreak following dormancy among cultivars ranged from early (May 14) to late (June 9). A higher vine survival rate was recorded in Sheridan (73%) compared to the Powell location (40%). Among the various cultivars studied, 100% survival was recorded in ‘Frontenac’, ‘Marechal Foch’ and ‘Osceola Muscat’, at Sheridan, while 60% survival and regrowth was recorded in ‘Frontenac Gris’ and ‘Elvira’ at the Powell location. Grapevine cultivars exhibit a wide variation in growth and developmental response to varying soils and climate. Vine establishment following planting, growth and development, flowering, berry development, and ripening also vary regionally. Such variation in survival rates may be attributed to the differences in soil, climate, and topography of the two test sites. We are currently evaluating flowering and fruiting characteristics of grapevine cultivars. Identification of cultivars suitable for specific regions of Wyoming will assist growers make the right choice of cultivar/s, improve production and enable a faster recovery of establishment costs.