The northern hemisphere has already begun to receive its coldest seasons, an indicator par excellence for cherries that it is time to start accumulating chill hours, a factor of great relevance in the reproductive cycle of cherry trees.
Why? This period is directly related to the use of reserves that the trees have to start the next season, in favor of the productive objective of achieving their potential in terms of quantity, quality and condition of the fruit.
For a correct accumulation of chill hours, cherry plants must have begun their physiological dormancy stage marked by the fall of 50% of their leaves (yellow leaf = fallen leaf); This should ideally occur during the months when the accumulated cold hours begin to be counted. If this condition does not occur naturally, we must resort to certain strategies to accelerate this process, which were explained in detail in previous articles.
Each variety has a different requirement for chilling hours according to its needs, based on the classic model of accumulation of chilling hours, that is, below 7.2ºC.
Why are chill hours so important?
The winter cold helps the plant to make available the reserves that it accumulated during the post-harvest, so it is relevant to take this factor and make it a part of decision-making, and not only in applications of dormancy breakers, it should also be considered for renewal pruning and load regulation, since cold is one of the indicators of fertility and production each year.
The cold reaches the plant as an ecological aid so that its reproductive and vegetative organs occupy these reserves and develop in optimal terms.
Thus, we may wonder if the applications of dormancy breakers are effective or if they must be used and the answer is: “it depends”, since the decision will be defined by the area, the variety, the rootstock, the state of fertility and Of course, the objective pursued; whether to accelerate flowering and harvest; partialize the harvest; decompress if there is a large surface of the same variety; synchronize flowering in varieties that need to be pollinated by others; or homogenize phenological states – considering that this last objective is governed by alternative dormancy breakers to hydrogenated cyanamide – therefore, there are many considerations to be taken.
The relevant thing is to be attentive to the accumulation of cold hours, compare them with previous years and thus have the necessary information to make decisions in the fields, for example in pruning or nutrition strategies, which will in turn allow making projections for the next season.