Grafting is a prevalent method for propagating ornamental conifers, particularly for species that exhibit irregular rooting characteristics when propagated via cuttings. This study investigates the efficacy of Cupressus sempervirens L. as a rootstock for grafting into ×Cupressocyparis leylandii and Cupressus macrocarpa ‘Goldcrest’ within a greenhouse setting. The technique employed was side veneer grafting, utilizing two graft combinations across a total of 396 grafted specimens. Growth was evaluated at four successive 45-day intervals after grafting (DAG), based on scion length, dry weight, and relative growth rate (RGR). The results revealed significant differences between the graft combinations, with ×Cupressocyparis leylandii showing higher graft compatibility than Cupressus macrocarpa ‘Goldcrest’. Additionally, Leyland cypress demonstrated enhanced biomass accumulation during the intermediate growth phases. While ‘Goldcrest’ registered elevated RGR values later in its developmental stage, this did not translate into an increased final biomass. The findings suggest that the C. sempervirens × Cupressocyparis leylandii graft combination is a more reliable option for ornamental nursery propagation in Mediterranean conditions.