Some Factors Affecting Supercooling of Fruit Blossoms

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Abstract
Summary Blossoming fruit trees in pots, detached blossom spurs and single blossoms were exposed, after various treatments, to low temperature in a cold chamber. Frost damage and supercooling were recorded. Ability to supercool decrease(j with increasing age of flowers. Severing of spurs or flowers from a tree favoured supercooling and, the smaller the detached part, the stronger was the tendency to supercool. Removal of wood and leaves from detached spurs increased the proportion of supercooled flowers and decreased the percentage of damaged ones, but spraying with water immediately before exposure to low temperature reduced the effects of these treatments. On the other hand, defoliation of spurs on trees in pots had no effect upon supercooling of flowers but showed a slight tendency to increase the damage. Varying degrees of competition for water between flowers, leaves and fruits were demonstrated. Studies of the effect of water supply to flowers before their exposure to low temperature showed that cutting of floral spurs under water suppressed their tendency to supercool as compared with spurs desiccated for 5 minutes, whereas partial desiccation increased the tendency towards supercooling. Frost damage to flowers wetted before exposure was higher than to dry ones. The degree and method of wetting was important. Wet flowers supercooled for a shorter time, and their supercooling points and “ indicated ” freezing points were higher than those of dry flowers. Widespread supercooling of blossom occurs in the orchard, but it is usually insufficient to protect from spring frost injury.

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