Fruit Growing Institute, BG - 4004 Plovdiv, Bulgaria
GANDEV, S., 2013. Winter hardiness of reproductive organs of the walnut cultivars Izvor 10, Lara and Fernor at extreme low temperatures in South Bulgaria. Bulg. J. Agric. Sci., 19: 1068-1070
The wide distribution of the species Juglans regia L. is due to its winter hardiness, which is different for the separate cultivars. The continuous spell of cold weather in Bulgaria in the period of deep winter dormancy of the walnut trees caused the minimum temperature drop down to minus 24.4°С. The aim of the study was to establish the winter hardiness of the reproductive organs of the introduced French walnut cultivars Lara, Fernor and the Bulgarian one Izvor 10. The results showed that the cultivars Izvor 10 and Fernor exhibited greater winter hardiness of the reproductive organs compared to Lara cultivar. It was established that within the same cultivar, the male flower buds (catkins) showed less winter hardiness than the female flower buds in Izvor 10 and Fernor cultivars. Growing the cultivars Izvor 10 and Fernor is recommended for the colder (northern) regions of the country where the mentioned minimum temperature of minus 24.4°С is often registered.