Growth potential, phenology, and cold hardiness were compared in progenies of 5 trees from each of 18 populations of Douglas—fir (Pseudotsuga menziesii va. glauca). Five—year—old seedlings growing in 2 nursery environments allowed assessment of population differentiation according to 6 variables related to growth and phenology. Freezing tests provided 5 variables that expressed cold hardiness in mid—September and near maximal hardiness. Statistical analyses of 11 variables suggested a differentiation of populations into 3 provinces. One province included cool environments, regardless of geographic origin. The remaining 2 provinces included relatively warm environments from either western Montana or eastern Washington and northern Idaho. Variation among provinces, among populations within provinces, and among trees within populations contributed to the genetic variance.