The tables below give the critical temperatures for various fruit crops at different stages of development. Though many environmental factors can influence the actual critical temperatures, these data give a good estimate of the temperatures at which to expect injury. To determine cold injury, cut branches after the cold event and warm them at room temperature for 24- 48 hrs before cutting buds to inspect for browning. Closed Flower Open Small Green Fruit Ave. Duration of temperature for damage can be 20 minutes to 2 hours, depending on wind, humidity, and cultivar.
Blueberries are more tolerant of spring frosts than most other fruit crops.
Open flowers are not usually injured unless temperatures reach the low to mid 20's. Brambles are also relatively tolerant of spring frosts and freezes, partly because the flower buds are not exposed until a few weeks after budbreak. However, brambles are one of the earliest fruit crops to bud out and are frequently damaged by freeze events. ID-168, the Indiana Commercial Tree Fruit Spray Guide contain a chart that describes the floral development stage and critical temperatures for several tree fruit crops not listed above. We'd like to hear from growers next week about the amount of damage that occurs.