Assessing Autumn Cold Hardiness in Newly Planted Fruit Trees and Grapevines

Low-temperature damage is one of the key factors that limits the distribution of tree species in an area. This damage in not always the result of low temperatures in winter or during bloom. Actively growing trees or parts of trees do not harden, may be injured by lower temperatures or erratic temperature fluctuations in autumn. It is essential, therefore, that the capability of each separate scion/rootstock combination to tolerate cold temperatures should be tested especially when the trees are young and a serious climate change is taking place. The overall goal of this study was to investigate the effect of early autumn temperature on fruit and grapevine species, included various cultivars and rootstocks, after plantings and to determine the cold hardiness. The autumn term of 2022 was one of the periods we have experienced notable temperature fluctuations, particularly in September. The day-night temperature difference reached 21.5 degrees on September 24. Subsequent field observations revealed significant variation in autumn cold tolerance among species, cultivars, and rootstocks. In this study, cold injury was observed in fifteen of the 29 examined species in the autumn after planting. During unfavorable autumn conditions, young trees of fig, persimmon, walnut, and chestnut cultivars were classified as very susceptible. It is most likely that the hardening process in these four species was more affected by erratic temperature fluctuations in the early phase of hardening.