Winter can be really cold!
…and that is Wonderful
because it means
What are chill hours?
Whether you read the Bible or listen to folk or pop music … it’s still the same.
“For everything there is a Season”
-Pete Seeger, 1958 or
-The Byrds, 1965
Most fruit trees follow an annual pattern of change, with each change occurring in one of the four seasons; awakening and rapid growth in spring followed by fruiting in summer, leaf drop in fall and rest in winter. These changes don’t just happen. Each is triggered by the characteristics of the season.
Most fruit trees will grow rapidly during the spring and first half of the summer because of the spring rains and increasing hours of sunshine each day. Later in the season, as the weather gets really hot, the growth rate begins to slow down.. there is too much son and it just gets too hot to bother growing… but the fruiting process continues! As days get shorter and cold weather sets in, deciduous trees drop their leaves in the fall. This is all triggered by the tree’s reaction to the length of day and temperature.
What actually happens in the fall is that the shorter days trigger the production of hormones in the tree that don’t just stop the tree from growing, they “prevent” the tree from growing. So, during the winter months, the tree remains at rest, a state known as dormancy, because of the presence of growth inhibitors
We all know that growth starts again in spring. Why does this happen? Does the warm weather spark growth? It turns out that it is the absence of the growth inhibitors that allows the tree to burst into growth again, and it is the cold weather of winter that breaks down the growth inhibitors within the tree. The number of hours of cold weather varies with each different variety of tree. For example, some kinds of peaches may require 1000 chill hours before the buds start to break open. Others only require 150 chill hours.Generally, a variety with a
Generally, a variety with a low chill requirement is generally defined as one needing 500 hours or less of accumulated cold below 45 degrees F. between mid-November and early February. In coastal areas of southern California, a “low chill” variety is considered to be one that needs less than 300 hours per season. Racking up those chill hours is quite a chore. So when winter comes, bring on the cold weather.