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Winter Cold Injury to Grapevine TrunksIntroduction |
Introduction
Winter cold injury (injury which occurs while the vine is dormant) can affect buds, mature wood (canes, cordons, trunks) or roots. The three tissues differ in cold sensitivity and in the impact cold injury has on future vine function. Trunk (cordon and arm) injury is the primary subject of the following pages.
Bud injury
Bud cold injury is discussed in a separate section (go there). Bud injury is more frequent than trunk injury, but usually there is a large surplus of buds. So long as it is not too extensive, vine pruning can be altered to compensate for bud cold injury..
Root injury
Vine roots are encased in moist soil. When soil water freezes heat is released (the heat of fusion) so that soil temperatures decrease more slowly than the air temperature. With prolonged cold, soil will freeze to depth, and temperature in the upper root zone may go well below the freezing point. In such cases roots will be damaged. In northern China vineyard sites are classified by how deeply the vines must be buried each year to prevent vine cold injury. In New York soils rarely get cold enough to cause damage.
We have relatively little knowledge about the specific temperature at which grape roots are injured or about differences in cold resistance among species, rootstocks or varieties. Roots exposed to sunlight appear become as cold hardy as trunks of the same variety. Root injury is primarily a problem during vineyard establishment because the vine has not yet developed deep roots which will escape exposure to damaging temperatures. Vines planted in shallow or poorly drained soil are more subject to root cold injury because of their shallow root system.