Among forest trees, poplars are important components of riparian ecosystems and are now accepted by the scientific community as ideal model to study perennial plants. They offer several advantages as a model system, including rapid growth, ease of cloning, prolific sexual reproduction, small genomic size and facile transgenesis. Our work has the objective to contribute to the knowledge of the genetic control of bud set in black poplar (Populus nigra L.). For this purpose the genetic variability (CVg) and the broad-sense hereditability (H2), at individual and genotypic level, have been examined in a full-sib family of black poplar (POP5) and in different European natural populations of the same specie grown in a common garden experiment. The full-sib family was obtained from parents selected from the germplasm collection (DISAFRI – University of Tuscia) from Italian natural populations, diverging for phenology and other adaptive traits. The full-sib family was planted in two sites in Central (Viterbo 42°25’N, 12°05’E) and Northern Italy (Cavallermaggiore 44°42’N, 07°40’E). The european natural populations were sampled in 5 different countries and 820 genotypes, from 15 metapopulations were planted in a common garden study in Northern Italy (Savigliano 44°36’N, 07°37’E). A randomized block design was defined for the establishment of the experimental plantations in each site. Six complete blocks were used with one replicated genotype randomly assigned to each block. The phenological study has been realized on the basis of a protocol designed to monitor the six phenological phases of bud set in black poplar. Data analysis have allowed to decompose the contribution of the different phases to the dynamic of bud set. Four phases characterized the process (phase 2.5, phase 1.5, subprocess 1 and subprocess 2) and two phenological points were useful to compare different sites (50% of individuals in phase 2.5 and 1.5). Preliminary results of the bud set phenology in P. nigra natural population will be also presented and compared to the full-sib family data. These results will be discussed in relationship to the photoperiod and temperature trend introducing, in prospect, the utility of this work for genetic improvement and mapping of QTLs associated to bud set.