They forecast another cold spell for this weekend as I write these lines. After this past week’s balmy weather, this could spell trouble for early opening buds.
But did you know that cold is good, if done right, for fruit trees and biennial plants like cabbage, sugar beet, celery or carrot? These plants all need to reach deep sleep through a cold period before they can blossom. Much like we rest through the night, apple trees, for example, typically need 1000 hours below 6 or 7 C, and not too much below 0 degrees through the dark season.
Of course we all know that much below freezing is called “freezing” for a reason! It’s no longer a chill, and much above 6 or 7 degrees makes some boys peel their shirts off. A chill is between 0 and 6 or 7 degrees, give or take.
1000 hours, that’s 42 days or a month and a half to you and me. The chill units don’t have to be sustained just like we don’t need to slumber through 6 to 8 hours of deep sleep every night (scientifically known as NREM Stage 3). It seems obvious, but is not clear to me, just how much fluctuation in temperature the trees can take before they are stuck in light sleep and fail to reach full dormancy.
Please let us know if you are a local fruit tree whisperer.
Different varieties and different species have varying chill unit requirements. Local weather records shows that most of February, much of January and some of December should qualify for plenty of apple tree chill hours, albeit not always continuously.
A third of the orchard trail has been planted three years ago and trees are looking fabulous, so we should see those trees bear a reasonable harvest thanks to the lovely cold. Provided the bees will fly at the time of blossom, and no hard frost will hit late, and the many other factors that make successful organic fruit growing a bit of a game of chance won’t come to fruition. Fingers crossed!
At least it’s nice to know that we have been shivering for a good cause, don’t you agree?