Freezing is a major environmental stress that inflicts injury to plant tissues and limits the productivity and geographic distribution of wild and crop species. Most tropical and subtropical species have little to no freezing tolerance. However, plants from temperate regions not only have some “constitutive” freezing tolerance (which is present all the time, typically at low levels), but they also have the genetic ability to increase this tolerance significantly when exposed to environmental cues that signal the arrival of winter, such as a period of low temperatures and/or short days. In temperate climates, such conditions are typically encountered by overwintering perennials in autumn, resulting in a seasonal increase in freezing tolerance.

The ability of plants to increase freezing tolerance in response to changing environment is called cold acclimation. The term deacclimation refers to reduction/loss of freezing tolerance originally attained through cold acclimation and, in nature, happens typically in early spring with the rise of temperatures. Depending on the depth of deacclimation, it may be either irreversible or reversed by subsequent exposure to low temperatures that may cause reacclimation, that is, restoration of at least a portion of the lost tolerance.