What makes trees begin waking up?

As I was out snowshoeing in one of my orchards I got to thinking…does increasing day length cause trees to begin waking up or is it temperature related? Both?

I ask this because I haven’t gathered scions yet and would hate to miss my window for doing so. I suppose I should get it done soon.

It’s temperature. After the chilling requirement is satisfied most fruit trees require a certain number of growing degree days of warmth before bloom. The base temperature is pretty low, not much above freezing. That’s why scions can begin to bloom even in the dark in a fridge.

If chilling isn’t fully satisfied and it warms up somethings like apples will still bloom but it takes a lot more heat. That’s why some high chill apples can bloom in June and July in low chill environments.


As long as its temperature, I’ll have no problem with them breaking dormancy anytime soon. Thanks

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Thanks for the detailed explanation.

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I have several trees in containers in an unheated garage. It can get below freezing but the temps are moderated compared to outside → not too hot and not too cold with no sunlight to speak of. Several apricots are waking up already, showing some color in the popcorn stage. Outside everything is still very dormant. This seems to confirm what fruitnut said. FWIW, on the same mormon apricot tree I have Flavor Queen pluot, Dapple Dandy pluot, Tomcot apricot and Zard apricot. The Zard doesn’t seem to be doing anything yet, the mormon apricot is swelling a bit, and the pluots and Tomcot are advanced. Flavor Queen is the most advanced by far.

The opposite of what makes them go dormant heat, more light hours, more rain/more watering (especially if the soil is high in nutrients). Yet heat and more light hours are the main causes of plants waking up.