Frost hardiness represents the ability of a plant organism to resist the impact of low sub-zero temperatures. It determines the critical threshold above which plant tissues undergo irreversible damage or death. Unlike overall winter hardiness, which also accounts for damping-off and the effects of thaws, frost hardiness focuses specifically on the cellular response to cold exposure.
This trait is genetically determined; however, its expression depends on the physiological state of the plant and the dynamics of external conditions. Frost hardiness is not a constant value: it increases during the period of deep winter dormancy and gradually decreases towards spring, as the plant loses its ability to resist cold due to dehardening.
The evaluation of frost hardiness during variety testing is conducted through laboratory freezing in controlled conditions or through long-term field observations of crop survival. For variety comparison, scoring scales, percentage of survival, or the determination of minimum permissible temperatures in degrees Celsius are used. Maximum realization of the innate genetic potential for frost hardiness is ensured by optimal sowing dates and adequate phosphorus-potassium fertilization in the autumn.