Cold hardiness of some exotic coniferous species used in landscape afforestation in the Central Anatolia

Blue cypress, Blue spruce, Western spruce, Spreading juniper, Eastern thuja and Leylandi are widely used exotic species for landscape plantations in cold-dry Central Anatolia Region. In order to better guide the species movement to Central Anatolia, their limits of tolerance to cold should be better known. Thus, we designed an experiment to quantify the cold hardiness of these six species. Here, one years old twigs sampled on February were exposed to cold of +4 (Control), -5, -10, -15, -20, -25, -30 ve -40 0C. Chlorophyll fluorometry (CF) and Visual observation (browning scoring) (VO) screening methods were used to assess variation in cold hardiness among six species. A non-linear model reflecting the relationship between temperature and tissue damage was fitted for each sample to find lethal temperature (LT50) for each species. According to our results, there are significant differences in frost tolerance among the tested tree species by both screening methods. The two cold damage screening methods used in this study (CF and VO) gave nearly the same results. Therefore, from a practical standpoint, our results indicated that Blue cypress, Blue spruce, Western spruce, Spreading juniper, Eastern thuja and Leylandii should not be planted in areas where the minimum annual temperature is below -20, -37 -36, -24, -27 and -22 0C, respectively.