Factors that impact dormancy

Factors that impact dormancy

The length of the day or darkness are some of the factors that impact dormancy
chilling requirement cherry

A couple of months ago, the cherry orchards began their dormant stage in the northern hemisphere, a stage that is already beginning to say goodbye and that had its beginnings, as usual, with the fall of -at least- 50 percent of its leaves. This is “ideally”, because sometimes and due to different factors, strategies must be used to force leaves to fall and thus initiate dormancy.

This winter lethargy is essential, because during this period the plants “rest” and metabolize their reserves to begin a new season of development. In this period, special attention is paid to the accumulation of chill hours, which, according to the specific requirements of each variety, is the main indicator of dormancy, since it can be concluded that the plant uses its reserves better if it meets these requirements. 

But there are also other components that are often not considered and that also have a relevant impact on dormancy. Rain directly influences the winter dormancy of plants, since the more days they are wet, the structures will have a better accumulation of cold.

On the other hand, another important aspect in terms of dormancy is the length of the day or darkness; It is worth mentioning that the first hint of dormancy occurs with the beginning of summer and the shortening of the photoperiod. This shortening causes the annual materials of the growing plants to present lignified basal sections, which affects the induction of flowers, accumulation of reserves, change in sap flow, and preparations begin to initiate dormancy.

In summary, rainier winters are probably also darker winters, with a shorter photoperiod, and that is an important component of dormancy.

But is it possible to determine that these factors, or the accumulation of more chill hours, can ensure the success of the season in terms of optimal production conditions? The answer is definitely no.

This topic requires a slightly more technical analysis. When we face a winter with these characteristics, it is often commented that there could be poor dormancy, because perhaps there is less accumulation of chill hours; However, this could vary if rainfall and photoperiod are considered as important factors in the quality of the dormancy period.

On the other hand, it must be considered that the accumulation of cold is super important in endodormancy, which is the central part of dormancy. During endodormancy, plants must accumulate at least 40% of the total chill hour requirement, therefore, there are many more factors and indicators that must be considered or measured to evaluate whether or not it is a good dormancy.

Clearly neither the chill hours, nor the rain, nor the photoperiod define a season, since there are other factors that affect cherry production. For example, in years of very good dormancy, but poor accumulation of degree days in spring, the normal development or metabolism of the plant is affected in terms of developing floral structures or fruiting, which could end with a bad year.

Also, if the dormancy is not so good, perhaps a very good spring would be enough to weigh that, sunny days, with good relative humidity, for all the pollination and fertilization processes to occur, and to have a good fruit set and a good result of productive potential. Therefore, it must be kept in mind that these are factors that do not entirely ensure the success or failure of a season.

Each season is different and has its own characteristics; The important thing is to have as much information as possible and also from previous years; This allows you to compare, evaluate and make decisions in an informed manner in order to achieve the productive potential of the orchard.

Read more about agronomic management here

Originally published in Spanish

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