Winter hardiness of sour cherries influenced by cultivar and soil moisture treatment

Winter cold is one of the most important risk factors in sour cherry growing in Latvia. Winter hardiness of sour cherries depends on the features of cultivars as well as on growing conditions. The research of flower bud and tree winter hardiness of seven sour cherry cultivars grown with drip irrigation and woodchip mulch was conducted in Latvia State Institute of Fruit Growing. The observations were made during four years. Winter hardiness of sour cherry trees was evaluated in the orchard. The air temperature dropped down below -25 degrees C, reaching even -28 degrees C after thaw in the second part of winter during some observation periods. The branches with flower buds were collected after the last winter frosts. Buds after swelling at room temperature were cut, evaluated visually and classified as partially damaged, completely damaged or undamaged; the percentage was calculated. Tree survival rate was determined in spring. The results showed that differences of bud winter hardiness among cherry cultivars were more pronounced than among soil moisture treatments. Sufficient winter hardiness of flower buds was detected for the cultivars 'Bulatnikovskaya', 'Latvijas Zemais', 'Desertnaya Morozovoi', 'Zentenes', 'Orlica'. The cultivar 'Tamaris' had lower winter hardiness of flower buds. The tendency for higher tree survival rate was observed in drip irrigation treatment. The cultivars 'Desertnaya Morozovoi' and 'Shokoladnica' had significantly lower tree survival rate than the other cultivars.