Frost hardiness of 16 European provenances of sessile oak growing in Scotland

The frost hardiness of 16 European provenances of sessile oak Quercus petraea (Matt.) Liebl. originating from six European countries was examined from autumn until budburst in spring using the method of relative conductivity. There were significant differences of frost hardiness between provenances and a strong relationship between phenology and frost hardiness. In spring, provenances that burst bud early dehardened earlier than provenances that burst bud later. In autumn, provenances that stopped growing early were more frost hardy than provenances that continued to grow. The interprovenance ranges of frost hardiness were greatest in spring and autumn and least in midwinter. Consequently, it was not possible to demonstrate significant differences of frost hardiness between provenances in December and January. Overall, German, Polish and Danish provenances were more frost hardy than French, Austrian and British provenances. French provenances were least hardy at all times.