Chapter 1

Annual Growth Cycle of the Grapevine

Dormancy

In the fall, the grapevine enters dormancy—the stage with no growth activity, which extends until bud burst the following spring. There are three main physiological stages related to dormancy and cold hardiness in grapevines—acclimation, the period of transition from non-hardy to fully hardy grapevines; mid-winter dormancy, the period of most severe cold and greatest cold hardiness; and deacclimation, the period of transition from fully hardy to the non-hardy condition and active growth.

Acclimation

The first stage in the dormancy process is acclimation, which begins after the vine has ripened its crop and shoot growth has ceased.

Mid-winter Dormancy

The second stage (maximum cold hardiness) occurs sometime during the mid-winter months. During this period of maximum hardiness, the grapevine may withstand low temperatures up to -20 degrees F (-29°C), depending on the variety.

Deacclimation

In the third stage, vines begin to lose their cold hardiness (deacclimate) as they readjust to warmer temperature conditions.

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