Winter Injury to Grapevines and Methods of Protection

If you live in the eastern half of the United States, a handy publication to have is this one from Michigan State University Extension called "Winter Injury to Grapevines and Methods of Protection".
This has been an unusual weather year for the Northeast, to say the least. Prior to Hurricane Sandy and the Nor'easter there was a freeze event on the early morning of October 13th that caused damage to grape leaves that were still green and photosynthesizing and I wanted to know what effect if any, this loss of leaves would have on the grapevine entering into dormancy. I turned to this publication that explains the process of cold acclimation of a grapevine for some answers. Cold acclimation is the process of transition of the grapevine from a cold-tender to a cold hardy state.
The potential for a grapevine's cold hardiness is determined by:

• The environment
• Cultural practices
• Genetic makeup of the cultivar

There are two stages of cold acclimation: (1)The first stage occurs in the late summer to early fall before any freeze events and is a response to the shorter days and lower temperatures. At this time, buds have not reached their maximum cold hardiness. (2) The second stage is induced by below freezing temperatures and coincides with the first killing fall freeze when temperatures drop below 32 ^oF.
As the temperature drops, the grapevines prepare for dormancy by:

• Formation of the periderm
• Mobilizing carbohydrate reserves to canes, trunks and roots
• Isolating dormant buds from the vascular tissues in canes and trunks
• Redistributing water in bud tissues leading to dessication

This is a very comprehensive publication that runs the gamut of topics from the economics of winter injury to how to manage winter-injured grapevines. Certainly a good book for me to read before we plant our grapevines and begin to deal with reality!