It is often assumed that forcing [for budburst] does not begin until after the chilling requirement has been met and this undoubtedly is what occurs naturally in boreal regions where extended periods of cold temperatures are never or rarely interrupted by warmer (forcing temperatures) until spring. We believe, however, that chilling and forcing can occur at the same time (in the temperature range where they overlap) and both systems are accumulating ‘‘time’’ over the dormant period. The systems involved in such accumulations (named the ‘‘memory of winter’’ by Amasino, 2004) are not understood.

From Harrington CA, Gould PJ, St.Clair JB: Modeling the effects of winter environment on dormancy release of Douglas-fir. Forest Ecology and Management 2010, 259:798–808.

The memory of winter