Any way to increase chill hours?

Hi all,

With chill hours seeming to go in the opposite direction globally (ie; less every year)…is there anything you can do to increase your chill hour accumulation?

I have a very small new urban orchard and was wondering if you have any tricks!

Thanks so much,

Sean B


Buy a bunch of bags of ice and dump it on top of the tree until you covered all the branches?



Not sure it would be much help for larger trees and really my only experience with this is with apples, but if you’re able to defoliate the trees about the time you think they should be dropping leaves it appears to help anecdotally here. I can’t say I’ve been doing it long enough to have a strong opinion of it though. I just pull off all remaining leaves on my trees sometime around late December. I zone push anyway, just a thought.

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I don’t know what the product is but a nearby orchard owner told me that he uses a spray (adds chill hours) approved for commercial and it wasn’t available to the general public. Some of the commercial poster might be able to answer better than I did.

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@fruitnut is a master on chill hours. Perhaps when he slows down a bit he can give some tips here to help you.

Hydrogen Cyanamid is used for improving bud break and bloom when chill accumulation is too low. Sold under the name Dormex. I’m not sure if it’s even available to non-commercial growers.


There are tricks but none easy or probably very effective without a lot of expense and effort. Shade helps a little bit. Evaporative cooling will add to that. Spray the trees with water once about every 5 minutes when it’s above 50F. Outside that’s not easy. In my greenhouse I can increase chilling quite a lot. But we have cold nights in winter, ave ~30F. So I increase chilling at night by heating the greenhouse to 37F. During the day shade and evaporative cooling can take 15F off the temperature. I can accumulate ~16 Utah hrs per day from mid Nov thru Febr. Outside is less than half that. Our winters ave 60/30F but range from 80 to 15F.