Dormancy is a phase in a grapevine growth cycle which occurs after the grapevine drops it’s leaves and ends in late winter to early spring. Dormancy phase helps vines to tolerate cold winter temperatures and has an important influence on grapevine flowering and vegetative growth in springtime. During the dormant phase, vines need to be exposed to enough hours of chill temperature for the bud break and normal spring growth to occur during the next season.
Although it may seem that nothing is happening with the grapevine during the dormant phase, that’s not exactly true. Little activities do occur – vines respire, for example – to maintain basic metabolic functions. During the dormant phase, grapevine survives based on carbohydrates reserves stored during the previous growing season, mostly as starch, in permanent wood structures, such as roots, trunks, and cordons. Since dormant vines must exist on their stored reserves from leaf fall until new shoot growth in spring, it’s extremely important to prepare vines well for resting.
Dormancy is not a uniform state within the development of plants, there are two types of dormancies during the winter, namely endo-dormancy, and eco-dormancy.