This study was carried out in the central part of Nestos Valley in northeastern Greece. The main objective was to examine the effect of different position (dominant, suppressed, side-shaded) and site productivities on the height growth of young Populus tremula L. clonal ramets in low elevation formations of the species. Fifty-four ramets growing in different positions and sites were cut and studied. Stem analysis was conducted and the height of each ramet at the age of 10 years was calculated. The main results of this research indicate that the dominant ramets on good productivity sites have greater height at the age of 10 years, when compared with the corresponding ramets on medium productivity sites. On the contrary, in suppressed and side-shaded ramets, there is no statistically significant difference in height at the age of 10 years between the two site types. This pattern indicates that competition is the procedure that characterizes the relationships between ramets in the investigated formations. The heights of dominant P. tremula ramets presented in this study are very satisfactory for the species, compared with the height of P. tremula trees from other regions of the species expansion reported in other studies.