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62 WINES&VINES June 2017 GRAPEGROWING WINE EAST and by N.W. Michigan after this date. Despite 600 acres of wine grapes being established in 1990 in the southwest, an increase in acreage was practically non-existent until after 2000. This reflection is also seen in the evolution of Vitis vinifera and resistant cultivar acreage since 1970. Until 1990, wine production relied heavily on an expanding number of resistant cultivars, while there were few new vinifera plantings. Throughout the decade, the total number of re- sistant plantings in Michigan plateaued at ap- proximately 600 acres, while vinifera acreage equaled that of resistant cultivars by the year 2000. Since that period, resistant cultivars have grown slightly, while vinifera plantings have continued to increase exponentially. In 2014, Michigan had 2,100 acres of vinifera grapes, almost three times higher than the total acre- age of resistant cultivars. The initial increase of vinifera plantings in both northwest and southwest Michigan during the 1990s may be explained by rising temperatures during the previous decade (see "Evolution of Wine Grape Acreage in Michigan"). Average grow- ing degree-days (GDDs) reached a peak in 1980 and were followed by conditions that were con- sistently suitable for growing vinifera cultivars. A similar pattern to that in "Wine Grape Acreage by Region and Type" is seen when accounting for the evolution of vinifera and resistant cultivar acreage between the two primary grapegrowing regions. Starting in 1990, vinifera plantings in north- west Michigan began to grow rapidly and have continued to flourish. Resistant cultivars now comprise less than 5% of wine grape acreage. Acreage of resistant cultivars in southwest Michigan grew steadily from 1970 to 1990. However, plantings of vinifera have since com- prised the majority of growth, and now each account for approximately 50% of the wine grape industry. Despite this recent change in growth, vinifera acreage in southwest Michigan is about one-third of that in the northwest part of the state, based on the voluntary responses to USDA surveys. Cultivar consolidation and regional cultivar identity Northwest and southwest Michigan are not only different in the ratio of cultivars planted but also in the total acreage of red and white vinifera cul- tivars. When total acreage is considered, north- west Michigan has more white and red vinifera cultivars than southwest. However, cropping level potential, based on historical averages, is different between the regions due to differences in GDD accumulation and growing season length. When potential cropping level is evaluated, northwest Michigan has almost four times the potential pro- duction of white vinifera wine grapes than the southwest, and both areas have essentially the same potential production of red vinifera. This is interesting given the difference in climate between northwest and southwest Michigan. Southwest Michigan has, on average, 30% more GDDs than the Northwest, which translates to a growing season that is traditionally two weeks longer than in northwest Michigan. The differences in climate are divergent enough to Wine Grape (acres) 2,000 1,500 1,000 500 0 Wine Grape (acres) 1,500 1,000 500 0 1970 1980 1990 2000 2010 Year EVOLUTION OF WINE GRAPE ACREAGE IN MICHIGAN These figures represent the increase of wine grape acreage in northwest (Leelanau and Old Mission Peninsula appellations, top) and in southwest Michigan (Lake Michigan Shore and Fennville appellations) from 1970 to 2014. Northwest Michigan Southwest Michigan Vinifera grapes Hybrid grapes Total wine grapes Vinifera grapes Hybrid grapes Total wine grapes Wine Grape (acres) 3,000 2,500 2,000 1,500 1,000 500 0 1970 1980 1990 2000 2010 Year WINE GRAPE ACREAGE BY REGION AND TYPE Wine Grape (acres) Evolution of wine grape acreage in Michigan. Top: The number of acres planted to wine grapes increased in all areas of Michigan from 1970 to 2014, but not at the same rate. Bottom: After trail- ing behind hybrids from 1970 to 1990, plantings of vinifera grew quickly from 1990 to 2014. Vinifera grapes Hybrid grapes 2,500 2,000 1,500 1,000 500 0 Total Michigan Northwest Michigan Southwest Michigan Top Five Acreage % / Total Acreage 110 100 90 80 70 60 50 40 30 CHANGE IN POPULAR CULTIVARS 1970 1980 1990 2000 2010 Year The five most popular cultivars of 1970 in north- west and southwest Michigan fell out of favor between 1985 and 2014. Southwest Michigan Northwest Michigan Number of Wineries in Michigan 160 140 120 100 80 60 40 20 0 1970 1980 1990 2000 2010 Year NUMBER AND DENSITY OF WINERIES Wine Grape (acres) / Number of Wineries The number of wineries in Michigan (top) exploded between 1995 and 2014, while the number of wine grape acres per winery (bottom) peaked in the early 1990s before normalizing. Source: Alcohol and Tobacco Tax and Trade Bureau (TTB) 50 40 30 20 10 0