Introduction of black walnut in southern Quebec: evaluation of 21-year-old full-sib families

Abstract

Black walnut (Juglansnigra L.) was introduced in the Québec City area 110 years ago. In the present study, we investigated performance of five full-sib families from controlled crosses among five selected cold-hardy parent trees of the introduced population. The number of seeds set per pollination bag averaged three, and seed germination was high (90%). At one fertile site close to the original plantation, the families showed normal growth, high survival rate, and good adaptability, as indicated by minimal frost damage. The average height was 3.1 m at 11 years, and 8.7 m at 21 years, reaching the height observed in native stands of black walnut. Therefore, the parent trees and their progenies could be used to produce seed for planting on similar sites. The results of this study demonstrated the importance of cold hardiness when introducing species into the northern temperate climatic zone.