Issue link: http://winesandvines.uberflip.com/i/573907
74 WINES&VINES October 2015 Winter Damage The challenge to winegrowing in the Great Lakes and northeastern temperate zone By Paolo Sabbatini and G. Stanley Howell T he sight of a normally beautiful and bountiful vineyard in any spring following a winter's dev- astation is depressing, with vine after vine and row upon row showing outright death or loss of aboveground vine structures right down to the soil or snowline. Be- yond the eye's immediate aes- thetic judgment, industry insiders and those with the knowledge may quickly leap to imagine num- bers of dead buds, percent of cane mortality or losses in the season's projected production volume. That was certainly the case in spring 2014 in the upper Midwest, where frigid arctic air masses rav- aged the region's sensitive vinifera vines. As field reports trickled in, it became clear that the year's yield would be much reduced— perhaps lost entirely. The resulting high vine mortality highlighted the necessity of either: 1) replant- ing and enduring the requisite three-year wait to return to full production, or 2) retraining vines with sucker shoots from the base of the trunk (from scion, above rootstock), with potentially only a single year's crop loss. This has happened before, and the region's growers and wine- makers have learned how to ad- just and move on, absorbing the losses and the lessons while re- maining generally optimistic. However, what was most unex- pected and tragic this time was the repetition of that devastating experience the very next year, in spring 2015, an unprecedented event that has rightfully resulted in thoughtful evaluation of the future of fine wine production from regionally grown grape- vines—a question of serious consequence. Grapevines in nature In nature, the survival of a plant species depends on maintaining its genetic diversity through cross- pollination, so that changes in its native environment can be readily accommodated. A similar rule of adaptation holds true for the cul- ture of any economic crop. For these, there are two key compo- nents that influence growth and productivity: a) the genetic consti- tution of the plant, and b) the abil- ity of those genes to be expressed not only in the environment where cultivated, but also under the man- aged conditions of culture. The situation is true for all plants regardless of life cycle, but it is especially important when cul- turing perennial plants with goals of plant survival over the dormant period, the production of both an economically acceptable yield and economically acceptable crop product quality. Further, they must possess the capacity to do this con- sistently over multiple years, since the perennial crops commonly re- quire a significant investment in years of initial growth when no economic yield is produced. Grape- vines epitomize this financial and agricultural challenge. What are the environmental limits for the profitable produc- tion of grapes? There are several, but in the Great Lakes and the northeast cool/cold-climate viti- cultural regions of the United States and Canada, the most limit- ing are the terrible and seemingly unpredictable winter freeze epi- sodes, which can push vines be- yond their threshold of survival. Unfortunately, this devastating prospect is an annual threat even in the face of a warming climate trend. The recent rise in acreage planted to grapes, fueled by ex- panding interest by states in the economic value of wine tourism, makes the losses no laughing matter. Further, the introduction of "super-hardy" resistant cultivars from breeding efforts in Minne- sota and Wisconsin has increased the potential for commercial viti- culture in regions where it was previously thought unacceptable, thereby expanding the boundaries for both gain and loss. However, for most of the relevant growing regions, damage from winter The appearance of a healthy compound bud (A) differs from the discolored tissues indicating death of the primary bud (B). A com- pound bud shows cold damage (C) to primary, secondary and tertiary buds. Compare healthy cane tissues (D) with moderate cold injury indicated by discolored cambium tissues (E). More ad- vanced symptoms of cold injury (F) will likely lead to cane death. GRAPEGROWING WINE EAST