The phenotype and adaptability of an individual tree is influenced by genetic and environmental factors. In this study, the genetic parameters of growth traits for 40 poplar clones at three different sites (Lishu, Cuohai, and Fujin) in northeastern China were investigated and analyzed. ANOVAs showed that all effects were significantly different (P < 0.001). The phenotypic coefficients of variation of different traits ranged from 14.84% (height in Lishu) to 23.61% (basal diameter in Fujin). The repeatability of the different traits varied from 0.81 (height in Fujin) to 0.97 (basal diameter in Lishu). Genotype × environment interaction models showed that populations G33, G38, and G32 were stable and high-yielding clones, and Lishu was considered an ideal test environment that was representative of poplar clone populations and allowed for discrimination between traits. The stability analysis indicated that some clones showed high basal diameters but were sensitive to environmental conditions, whereas others had moderate basal diameters but were adapted to environmental conditions, which suggested that elite clones should be selected separately for different sites. Based on the growth traits, with a selection rate of 10%, four clones were selected at each site, and the genetic gains of growth traits ranged from 9.99% (height) to 25.45% (basal diameter). These superior clones will provide materials for forestland renewal in semiarid regions, and the results in the present research contribute to a theoretical foundation for the selection of poplar tree individuals.