Most soft fruit and top fruit, with the exception of figs, are very hardy while dormant over the winter as temperatures do not fall low enough to harm these trees in Britain. Gardeners in more severe climates may need to choose cold-resistant rootstocks and cultivars.
However, in early spring, the new growth and blossom can be easily damaged by frost. Not only are plants in full flower vulnerable, but buds and even fertilised flowers can be damaged, so protection should be maintained for two weeks after flowering if severe frosts threaten.
Frost occurs when temperatures fall below 0ºC (32ºF). On clear nights warmth is radiated out and lost. Cold air forms on trees and other objects and being heavier than warm air sinks to the ground, displacing warm air. Objects near the ground then become chilled and freeze. Cold air naturally flows downward on sloping ground, collecting at the lowest point or against a barrier. If this barrier is a fence or hedge consider creating a gap, or remove some of the lower growth to improve air drainage. If there is no alternative, plant the larger fruit trees at the bottom and the smaller ones on the higher ground.
Wind frosts, where freezing wind blows into the fruit garden, are much less common and usually only affect exposed hill top gardens.