The paper presents summarized data of longtime (the period of 1961-2006) phenological observations of apple trees (Malus domestica Borkh.) in Lithuania. It has been determined that in different localities of the country apple trees start flowering on May 11-17 (± 3-5 days); the average in Lithuania is May 16. Evaluation of the changes in the dates of the beginning of apple tree flowering revealed that, due to climate warming during the last decade, apple trees start flowering 4-5 days earlier

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... an the longtime average. The thermal regime of April strongly influences the annual changes in the dates of the beginning of apple tree flowering: the correlation coefficient between the mean monthly air temperature and dates of the beginning of apple tree flowering is-0.48-(-0.80). The possibility to forecast the dates of the beginning of apple tree flowering based on the dates of the beginning of the flowering of European hazel (Corylus avellana L.) and European bird cherry (Padus avium Mill.) was investigated. It has been ascertained that the date of the beginning of the European bird cherry flowering is suitable for forecasting the date of the beginning of the apple tree flowering because that date significantly correlates with the beginning of the European bird cherry flowering, which is an indicator of true spring.