To succeed, the trees must be able to sense the impending onset of winter and prepare accordingly.
For many species, the appropriate signal is the shortening days of autumn, while for others it is the cooler temperatures of autumn. For the grower, it is also important to know how to break dormancy so that the trees can again grow and develop.
Experiments have indicated that many trees have a critical chilling requirement and this must be met before dormancy can be broken. Dormancy breaking is then followed by a need for heat to enable flower formation and development.
Trees that receive insufficient chilling can exhibit delays in bud burst, low rates of bud burst and lack of uniformity in leaf production and blooming. Each of these will lower fruit yields.
The review also discusses the genetic control and molecular biology of dormancy as well as cultural practices that can sometimes overcome insufficient chilling.
Climate change is clearly producing warmer winters that also create challenges for growers because individual trees are expected to have a life of at least 25 years. The review is intended to raise awareness of this problem among politicians, plant breeders and scientists.
Dr Ken Cockshull, Associate Fellow, Warwick Crop Centre, University of Warwick
Dormancy in Temperate Fruit Trees in a Global Warming Context: A Review by Campoy, Ruiz and Egea (2011). Scientia Horticulturae 130 (2): 357-372. The contents of issues of Scientia Horticulturae and abstracts of papers are provided at www.elsevier.com/locate/scihorti.