Chill Hours and Darkness

I was thinking of chill hours and darkness on my way into the farm this morning. As I passed the frosty hillsides embracing Marsh Creek, I wondered if the trees on the hillsides need chill hours like our stone fruits do. I notice the elderberries blooming at the same time every year and think about the amazing mechanisms engineered into plants to assure their survival.

Chill hours and darkness affect humans and plants in some ways very similarly. When it gets cold and dark, I want to hole up in my warm house and reduce my activity. Plants respond in much the same way. They withdraw the sugars from the tips of their branches and get prepared for a state of extended dormancy. As darkness increases, hormones in plants signal "sleepy time!" This leads to a drop in photosynthetic activity. Leaves fall and sugars and proteins concentrate in cell protoplasm creating a sort of anti-freeze within the plant.

Chill hours actually work on the other end of the seasonal cycle, triggering bloom time. If a tree doesn't receive the chill hours it needs to break dormancy, it may bloom haphazardly, resulting in the possibility of its missing prime pollination time and having low fruit set. I don't know much about it, but I do know that when the cold weather comes, stone and pome fruit farmers revel in the cold, thinking of the good it does their trees. We all count the hours of chill knowing that they make for better production and healthier trees.