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October 2015 WINES&VINES 77 WINE EAST GRAPEGROWING trunk replacement canes, enhanc- ing their survivability. In summary, overly vigorous growth during vine recovery from freeze damage is undesirable and leads to increased temperature sensitivity and poten- tial for future freeze damage to perennial vine structures. Viticultural practices enhancing protection for the future Covering and uncovering the graft union of the vines each year are certainly labor-intensive processes, yet they remain the most efficient and effective techniques to guar- antee the survival of vines and fruiting canes for the following season. Soil is an excellent insula- tor. Cold winter temperatures only a few inches below the soil surface are rarely damaging, and they gen- erally remain around the freezing point—even with much colder air temperatures just above the soil surface. Commercial growers em- ploy a grape hoe to mound the soil in the fall and remove the soil in the spring, before the vines resume their active growth. The timing of soil removal, of course, is critical to prevent root growth from the scion cultivar instead of the rootstock cultivar. Unions on grafted vines should be covered with a few inches of soil for the winter months, thereby protecting scion buds close to the graft union that could be very im- portant in the case of severe win- ters damaging or killing the buds above the mounded soil. In 2012, the USDA released a new plant hardiness zone map in response to the observed tempera- ture increase around the United States. Growers in the regions discussed here are using the extra heat (growing degree-days) and the longer growing season to ripen cultivars that were impos- sible to grow only a few decades ago in cool- and cold-climate viti- culture. Unfortunately, this warm- ing trend is also generating winter temperature volatility, especially in the extreme lows, and it re- quires reconsideration of basic methods of grapevine protection during the winter to maintain eco- nomically sustainable viticulture (see graph on page 78). The low winter temperatures in our re- gion are something we cannot avoid. The frequency probably will change, but not at the inten- sity demonstrated in the graph, which shows multiple killing tem- peratures in every decade since Insulation of vinifera vines with soil (or mulch) by hilling up above the graft union has provided the best protection from cold damage (especially to the graft union area and those viable scion buds above the union). 716.542.3000 WWW.NIAGARALABEL.COM 716.542.3000 WWW.NIAGARALABEL.COM digital printing flexo printing screen printing embossing hot & cold foils specialty papers advanced VDP digital printing flexo printing screen printing embossing hot & cold foils specialty papers advanced VDP Natural Corks Champagne Corks Twinline Corks Bartops VISION Synthetic Corks G-Cap® Screw Caps Sales Representatives: Chris & Liz Stamp info@lakewoodcork.com lakewoodcork.com 4024 State Route 14 Watkins Glen, NY 14891 607-535-9252 607-535-6656 Fax PIONEER INNOVATOR PARTNER MSU EXTENSION VITICULTURAL STRATEGIES TO MITIGATE THE IMPACT OF WINTER COLD • The retention of multiple trunks and extra canes and buds, coined by Dr. Bob Pool as "spare-parts viticulture." • Always having multiple replacement canes (suckers) growing under the vine, which is critically important for grafted vinifera cultivars. • Sufficiently insulating the graft union with soil during winter. • Using cultural practices designed to achieve vine balance. Mul- tiple trunks provide protection to extreme cold temperature and for varieties particularly sensitive to cold.