The ongoing fast climate change is currently affecting the physiology and distribution of species. When projecting future species repartition, most prediction models don’t take into account the evolutionary mechanisms behind species response to changing parameters. The aim of the study was to characterise the adaptive capacities of populations by (i) studying the extent to which the stomatal variations are under genetic control (adaptation) or under environmental control (phenotypic plasticity) and (ii) identify the environmental parameters which trigger a stomatal response. The study focused on a Sessile oak (Quercus petraea (Matt.) Liebl), a broadleaved species largely distributed throughout Europe. Leaves were collected from four common gardens among Europe (France, Denmark, Poland, England) with each of them gathering seeds originating from 10 European provenances. Investigations on Stomatal response were conducted through the study of stomatal density SD and size SS. To disentangle local adaptation and phenotypic plasticity in stomatal response, Linear Mixed Effect Models were studied for each of the stomatal traits and used as explanatory variables the trial site, seed provenance origin and an interaction term between provenance and trial. For both stomatal traits, interaction with the environment (trial site) was the first predictor in explaining the observed variability. Phenotypic plasticity appears as the main reaction mechanism in oaks. For both models, there was a genetic variability in the phenotypic plasticity displayed. Finally, if low evidence of local adaptation process were found, an adaptative lag appears when testing the effect of Temperature of mean temperature of warmest quarter ecodistance on Stomatal size. A significant negative correlation was found between the stomatal size and the trial’s mean temperature of the wettest quarter (1987-2019 period), precipitation of spring 2021, and 2020 annual precipitation. These results suggest that heat and dryer environments lead to a leaf response through stomata reduction to avoid water depletion. Correlations with the stomatal size and the seed’s provenance site precipitation regime (annual, seasonality, in the driest quarter for the 1961-1990 period) suggest that trees originating from drier climates tend to have smaller stomata. Stomatal density trait was less correlated and exhibited inverse tendencies than stomatal size. To conclude, global warming is a quick process which calls for a fast response of trees to changing habitat. Hence, the high oak plasticity observed in our experiment is a good sign as to the ability of the oaks to maintain themselves. This reinforces the statement of oak as a resilient species. If our study didn’t highlight limits in the plastic response expressed by oaks to changing conditions, phenotypic plasticity may not be sufficient to ensure the adjustment of phenological traits to climate change. Thus, oaks could be forced to adapt via migration.