CHANGES IN THE FREEZING STRESS RESISTANCE OF THE CRANBERRY LEAF, FLOWER BUD, AND FRUIT DURING GROWTH AND DEVELOPMENT
A sharp increase (from -18°C to -2°C) was observed in the lowest survival temperature (LST) for the flower buds as they lost dormancy and started to open, between late April and early May. A sharp decrease in the LST for newly formed flower buds in the last week of October was found and it reached the lowest LST measured of -22°C in early November. Flowers and small fruits were very susceptible to freezing (no hardier than 0°C). The LST of the fruits changed from 0°C to -8°C and from 0°C to -3°C in 1986 and 1987, respectively, as the fruits changed from green to red stage of development.
Overwintering leaves lost their cold hardiness rapidly from late April to early May (from <-24°C to -7°C). Newly formed leaves changed their hardiness level from 0°C (very early in the growing season) to about -7°C in mid-July, to -24°C in mid-October, and then to <-24°C in mid-December.
Abbreviations: FRT, frost killing temperature, LST, lowest survival temperature.