Freeze damage depends on tree fruit stage of development

Damage from freezes depends on the development stage of the fruit crop. These tables allow you to quickly asses the risk for your tree fruit crops

During the winter, fruit trees can withstand very cold temperatures. As fruit trees develop in the spring and buds start to swell, they lose the ability to withstand cold winter temperatures. The young, actively growing tissues will be damaged or killed by warmer and warmer temperatures. Swollen fruit buds can often withstand temperatures in the teens without any damage. As the buds open, temperatures in the low 20s can cause harm, but leave other buds undamaged.

Early in development there is often a wide range between the temperatures that cause little damage and those that cause severe damage. As bloom nears, temperatures in the upper 20s can cause considerable harm to an early blooming species or variety and leave other fruit crops unaffected or with only slight damage. Near bloom, the range between slight and severe damage is very small. The stage of bud development determines how susceptible any given fruit crop is when freezes occur.

I have posted two tables for the critical temperatures of tree fruit during development. Tree Fruit Critical Temperatures is a table of common tree fruit with budstage names and the critical temperature ranges that will cause between 10 and 90 percent injury to the flower buds, all on one page. Picture Table of Fruit Freeze Damage Thresholds includes the same information and includes pictures. This table is three pages long.

Unfortunately, spring freezes are almost a certainty. Fruit growers need to constantly assess the stage of development of their crops and the susceptibility to freeze injury. During this unusual spell of warm weather, fruit trees will develop quickly and the critical temperature will rise from the teens to the 20s, to levels just below freezing at bloom time.

Related Michigan State University (MSU) Extension News article: Monitoring for the risk of frost and freezing temperatures.

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