Freezing Temps on Apple Trees

Freeze Limits

• The extent of damage that an apple tree suffers due to freezing temperatures depends on the stage of growth the tree is experiencing when the cold snap strikes. During its dormancy period, the apple tree withstands temperature ranges from 28 degrees Fahrenheit to as brutal as minus 60 degrees Fahrenheit. But as spring beckons, and buds begin to develop, the ability of the tree to withstand freeze damage lessens.

Bud Fatality

• The temperature at which buds will be killed is called the critical temperature and defines the temperature that new buds can withstand for 30 minutes before lethal damage occurs. When the apple tree is about to bloom, a temperature of 28 degrees Fahrenheit is likely to kill 10 percent of the buds, while a cold snap to 24 degrees Fahrenheit will prove fatal to 90 percent of the emerging buds. Typically, trees planted at a higher elevation or buds in the upper section of the tree experience less damage.

King Bloom

• The king bloom is the flower situated in the center of a cluster of buds and possesses the potential to grow into the largest fruit of the bunch. Unfortunately, because it is the most advanced in terms of growth and bloom, it is also the most susceptible to freeze damage. Often, frost or freeze kills the king bloom. If the side blooms are growing larger than the middle bloom several weeks after a freeze, it is safe to assume that the king bloom was destroyed earlier due to a spring freeze.

Damage

• If apple buds are clustered tightly together, gardeners can cut across the buds lengthwise to determine if any of the buds were damaged. As the blooms continue to grow, petals will show a browning that indicates damage from a freeze or frost. Even if the flowers survived a freeze, the forthcoming fruit may show a condition known as frost ring -- a brown stripe that runs across the diameter of the fruit. In addition to damaging the aesthetic value of the apple at harvest, frost ring also restricts the total growth of the apple.