What Happens During Winter Out In The Orchards?

In our Delta area, we have fluctuations of temperatures during both Fall and

Winter, with sometimes warmer periods and some times of near or actual frost. Because of this factor, the Dynamic Model from the Chilling Accumulation Models is used; the term, dynamic, referring to the often moving of temperatures here.

During the time of dormancy, we need those long periods of very cold hours below 45ºF., but several days of warmer weather during this time can cancel out some of the colder hours, resulting in a too-early bloom or partial bloom.

So, our consultants use the term “chill portions” which are units calculated using the number of hours of temperature ~35-55ºF, from September 1 of the year. More on this for you math maniacs at the University of California Fruit and Nut Research & Information Center, here.