Abstract

Thirty-five broadleaf evergreens which are evergreen in USDA cold hardiness Zone 7 were screened using leaf discs in the laboratory for Zone 6 (-20C) temperatures. Field data were collected from the plants in the field after two consecutive nights with lows of-20C. Correlations between lab and field scores were high, demonstrating the usefulness of leaf discs in initially screening broadleaf evergreens for evergreeness. The method allows for a more thorough sampling of a taxon and may therefore give better results than using a limited number of larger leaf samples, such as whole leaves. A number of the tested taxa should prove evergreen in Zone 6, including: Camellia oleifera Abel ‘Lu Shan Snow’, Viburnum L. Arrowwood ‘Conoy’, Viburnum rhytidophyllum Hemsl. ‘Cree’, and certain selections of Pyracantha M.J. Roem, Illicium anisatum L., Quercus acuta Thunb., Quercus myrsinifolia Blume and Daphniphyllum macropodum var. humile Miq.