Chapter 28

Winter Protection of Grapevines

Cold Hardiness in Grapevines

Grapevine cold hardiness is a dynamic process and changes throughout the dormant period. Beginning in early fall as the vine prepares itself for dormancy, the tissues begin to acclimate. This is a gradual process and, in grapevines, acclimation is in response to shorter day length and cooler temperatures. It is complex in nature and involves many factors and mechanisms. As temperatures drop to sub-freezing temperatures, the vine becomes more cold tolerant and achieves maximum cold hardiness just prior to the coldest periods experienced mid-winter, and is maintained until external temperatures begin to climb at the end of winter. As temperatures begin to increase in the latter part of winter, the vine has already completed all of its requirements to break dormancy and will begin to deacclimate.

Acclimation

Cold acclimation is the process leading to the development of freezing tolerance in grapevines. Grapevines, like other woody plants, gradually acclimate to low temperatures in the autumn in three stages.

Deacclimation

Deacclimation occurs as the vines prepare to leave cold winter temperatures and begin to resume active growth as daylight periods lengthen and temperatures rise in the spring. During deacclimation, progressively warmer temperatures enable the vine to begin to have water redistribute back to proximity of the bud cells.

Assessing Cold Hardiness

What is Cold Hardiness?

Cold hardiness is the ability of a grapevine to withstand low temperatures.

What is LTE?

LTE in technical terms is the Low Temperature Exotherm as measured by freezer testing.

Click on the following topics for more information on winter protection of grapevines.