Bud phenology and development of needle nitrogen content were monitored on Norway spruce (Picea abies [L.] Karst) and European beech (Fagus sylvatica [L.]) trees grown inside glass-domes for five years under ambient (385 µmol(CO2) mol−1) and elevated (700 µmol(CO2) mol−1) atmospheric CO2 concentrations ([CO2]). The spruce to beech ratio was 35:65 in both treatments. At the beginning of the experiment mean age of investigated trees was 5 years.Elevated [CO2] was responsible for premature growth of both spruce and beech buds in the E treatment (not significantly, by 3–7 days). Nevertheless the flushing of neither beech nor spruce was not significantly hastened in E treatment during the flushing within the 5 years. During the second half of flushing faster development of terminal beech buds comparing to spruce was found (Chi-square = 65, p 2] acts as growth stimulator but the nitrogen insufficiency eliminates a positive effect of [CO2]. As the global climate change express itself in many ways and relationship’s consequences among plants and/or animals are hard to forecast.