Provenance variation in phenotypic traits in Quercus robur and Quercus petraea in Danish provenance trials

A study of 33 provenances in Danish field trials with Quercus robur and Q. petraea was made between 1993 and 1998. The trials include Danish, Dutch, G erman, Norwegian and Swedish provenances, and were established between 1900 and 1988. Growth, flushing, stem form and epicormic shoot formation were s tudied. There were strong geographical dines for growth; however, the varia tion within regions was considerable. Time of flushing followed a more comp lex clinal pattern and was related to both latitude and distance from the o cean. Stem form was highly variable within different geographical regions a nd it is suggested that this could be caused by different management regime s in the past. Oaks from some locations in Sweden and Norway seemed especia lly straight. Stem form is one of the most important parameters for commerc ial oak management and could be seriously improved through breeding, as it was under considerable genetic control. Epicormic shoot production was in p art under genetic control, but no geographical patterns were found. Danish provenances of Q. petraea were growing more rapidly than similar Q. robur o n sandy locations, Quercus petraea produced fewer epicormic branches and st em form was equal to or better than Q. robur. Quercus petraea should be rec ommended for landscape use on windy locations in Denmark.