The “Réseau d'esssais des plantes ligneuses ornementales du Québec” (REPLOQ) is a research project initiated in 1982 with the mandate to elaborate, develop and coordinate a cooperative research project to evaluate the winter hardiness of ornamental plants. Systematic evaluation trials provided information on growth potential and hardiness of woody trees and shrubs evaluated over a five year period in the principal growing regions of Québec. Zonal range covered was 2 to 5b in the Canadian system. Adequate field testing is critical for new introductions and, since 1984, more than 400 species and cultivars have been introduced in 8 evaluation sites. Results were published on several forms: technical factsheets provide cultural and production recommendations for the species and cultivar evaluated in each climatic zone. Propagation methods as well as their potential for ornamental purpose were described. In the 1984 plantation, Malus baccata and Quercus macrocarpa showed a similar potential for acclimation, but Malus baccata could be produced advantageously in any area, while the production potential of Quercus macrocarpa was enhanced by the summer heat of the wannest region. In this group of plants, Acer saccharinum was the species with the greatest number of plants suffering winter damage and could not be grown without risk anywhere in the area studied. Acer platanoides was severely damaged in the coldest of the eight evaluation sites and should not be cultivated there.