Determination of the dates of the sweet cherry trees  dormant period completion and beginning of flowering

DOI: 10.35205/0558-1125-2020-75-132-136

UDC  634.1.001:634.23 (477.7) 



M.F.Sydorenko Melitopol Research Fruit Growing Station of the IH NAAS of Ukraine, 72311, Melitopol, 99, Vakulenchuk St., e-mail:

The author presents the results of evaluating the phenoclimatographic models application for determining the dates of the sweet cherry trees dormant period completion and beginning of flowering in the soil and climatic conditions of the South Steppe of Ukraine as well as the effect of the external factors (maximum and minimum air temperature), as the models parameters for the generative buds growth and development. The limit values of the phenoclimatographic indicators were established: CU (chill unit) required for the cultivar Krupnoplidna dormant period completion  and GDH (growing degree hour) specified for the beginning of flowering. In order to emerge from  the mentioned period completion cherries need to accumulate – 1350 оС CU, and for the beginning of flowering – 4839 оС GDH. The dates of the biological dormancy completion and flowering were based on these limit values of CU and GDH. The validation of the models by comparing the calculated and actual dates of the flowering beginning in the orchard showed that their divergence was in the range from 0 to 3 days. That is indicative of the high prediction accuracy of these dates. The intensity of the generative buds  development appered depend on their physiological state, which was influenced significantly by the environment temperature conditions, first of all, maximum and minimum air temperature. After the accumulation of 43 % of the GDH limit index the period of the accelerated growth processes rate in the buds began which lasted just until the beginning of of the sweet cherry trees flowering. This occursed mainly in the period with positive air temperatures. 

The studies showed the possibility of using the phenoclimatographic indicators limit values: CU – for the selection of varieties with the late time of the dormant period completion, and GDH a criterion of the plant resistance to the negative effect of the spring frosts.

Key words: sweet cherry, phenoclimatographic models, CU, GDH, generative buds, dormant period completion, beginning of  flowering. 

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