Frost resistance of some sweet cherry cultivars in the Bucharest area.

Sudden low temperatures could occur in the spring when some of sweet cherry cultivars are more susceptible to freeze and floral buds injuries. These are delicate moments for growers year by year. In this study, differences in cold hardiness and lethal temperatures were observed during the same phenological stage (bud burst) for the same cultivar as well as among tested cultivars ('Katalin', 'Kordia', 'Burlat', 'Rivan' and 'Regina'). It was used the frost induced method for determining cold hardiness of cherry buds (-7�| C/0,5h; -7�| C/1h; -1,5�| C/0.5h; -1,5�| C/1h; -2,5�| C/1 h). The injuries observed were highly dependent on the stage of development of flower buds. Progressive vulnerability of the bud to low temperatures was observed. During 2012-2014, it was noticed that the cultivars were sometimes sensitive, semi-sensitive or hardiness, varying with the amount of active temperatures over 7�ˆ C. Although the determination of the maximum hardiness is genetically attainable, the description of changes in hardiness is possible; more years of observations are needed as a result of the strong climatic influence.