Winter chill and cherry fruit set are two different but related subjects, each affecting results at harvest.
Here are some factors that come into play.
Water stress
A common practice for some growers is to provide a deep irrigation after harvest and then let stress take hold to induce fruit buds.
After all, nothing promotes bud development like the promise of an early demise for a cherry tree! That is, providing it does not result in tree death…
Some cherry regions have to keep watering to maintain the trees and keep them living. The stress leads to earlier change in leaf colour and then chill hours, or portions, may start to accumulate earlier than they might because of earlier defoliation.
Although rainfall may play a part in this strategy, it is fairly unusual to get sodden soils post harvest from excessive rain.
Induce earlier defoliation
Spraying to induce earlier defoliation by using recommended copper and/or nitrogenous fertilizers will also allow an early start to chill hour portions.
Limb removal
Post harvest removal of limbs that block light from penetrating the canopy is useful for inducing fruit buds.
Failure to remove those light–blocking limbs will result in the fruit being produced mostly at the top of the cherry tree, which is neither economically sound nor productive.
Dormancy breakers
The use of registered dormancy breakers can come into play as a final strategy, either to break dormancy, to induce more even flowering, or to bring a pollinator into the same flowering zone as another variety in order to increase fruit set.
Experimenting
Many cherry growers are prone to experiment to learn what works for them. Remember, every year is different.
As an American grower said recently, “ I just had my 47th consecutive year of not having a normal year!”.
For information see Tree Fruit March 2014
