Pomological Characteristics and Ploidy Levels of Japanese Plum ( Lindl.) Cultivars Preserved in Poland.

Research on the resistance to frost, susceptibility to sharka, flowering biology, fruit setting, yield, and ploidy levels of 36 Japanese plum cultivars (mostly hybrids of with ) were carried out in 2015-2020 at the Experimental Orchard located in Dąbrowice near Skierniewice. Relatively mild winters with sporadic temperature drops to nearly -21 °C in January of 2017 and 2018 caused slight damage to several cultivars of Japanese plum insufficiently resistant to frost. The trees of most cultivars remained healthy, with no signs of damage.