Analyses of flowering phenology were carried out at Újfehé rtó, Hungary and Oppenheim, Germany. In our long-term project, 88 sour cherry cultivars from Újfehértó and 105 cultivars from Oppenheim were evaluated over 27 and 12 years, respectively. All sour cherry cultivars from Újfehértó are characterized by the same late flowering period, which generally started on the 111th day (Julian days) of the year and finished on the 121st day. Besides genotype, several external factors have been shown to significantly influence the start of flowering period, which was closely correlated with the differences between day and night temperatures over the 30 days before flowering. In Oppenheim, 'Gerema' and 'Schattenmorelle' were characterized by extremely late bloom dates. Sour cherry cultivars selected in the region of NorthEastern Hungary are characterized by high fruit set after open pollination, exceeding 20%. The highest fruit set ratio (26.9%) was obtained with 'Petri'. In Oppenheim, 'Schattenmorelle' was characterized by 15-20% autogamous fruit set, while open pollination set approx. 30-40% of fruits. In Újfehértó, over 27 years, flowers were destroyed by serious frost injury in two years. Based on several characteristics, the two late blooming cultivars that have been recently released, 'Petri' and 'Éva', appear be promising choices for commercial orchards in Hungary.