Now for something different. Our mild winter for the most part anyway has had horticulturists talking about "Chilling Hours". This is all about our temperate plants getting enough cold weather to know it is time to come out of winter dormancy and begin to grow come spring. Chilling hours are recorded at weather reporting stations along with the rest of the weather data. Chill hours are recorded for temperatures between 32 and 45 degrees. Temperatures below 32 degrees are not counted as plants are completely dormant. Any wintertime temperatures above 60 degrees are subtracted from the totals. Our temperate landscape plants having evolved over the millennia have their own way of keeping track and know when it is safe to break winter dormancy. This explains why some fruit trees are damaged by a late frost or freeze, they have already received enough chilling hours earlier and are attempting to grow. Fortunately for the plants native to our area, their chilling hour requirements are higher so they break dormancy without the risk of having flower buds or leaf buds damaged by late frosts. Examples for fruit trees depending on varieties are:
Chill Hours Required to Break Dormancy Using the 45oF Model
Apple 800 to 1750
Pear and sour cherry 600 to 1500
Plum (Japanese) 600 to 1600
Cherry (sweet) 500 to 1450
Peach 375 to 1200
Apricot 300 to 1000So go about your gardening and fruit growing like everything is normal, because it is.