Frost Tolerance of Apricots and Peaches

Growers of apricots and peaches often wonder at what temperature fruit buds are killed especially in years where we have an early spring.  These two tree fruits bloom very early and are often caught by a late frost. The following will give you some guidelines but remember that the actual damage is going to be influenced by the weather before the temperature drops. An extended warm spell before the cold snap may result in more damage due to a loss in cold hardiness. The stages listed are for the fruit buds.

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Apricot

Stage	10% Kill (°F)	90% Kill (°F)
First white	24	14
First bloom	25	19
Full bloom	27	22
In the Shuck	27	24
Green Fruit	28	25

 

Peach

Stage	10% Kill (°F)	90% Kill (°F)
Swollen bud	18	2
Half-inch green	23	5
Pink	25	18
Bloom	27	24
Petal fall	28	25
Fruit set	28	25

 

To check for low temperature injury to fruit buds or blossoms, use a sharp knife and cut them in half longitudinally (from top to bottom). If the tiny seed in the center is white to cream color no damage has been done. But if the seed in several buds or blossoms is dark brown or black, it has been killed.

It is possible to give some protection to blossoms from freezing by covering the tree with a bed spread, blanket or similar fabric. It is best of the material reaches the ground so that heat given off from the soil is captured.  Old-fashioned Christmas lights distributed through the tree will help to give added protection. The newer, smaller Christmas lights do not give off enough heat and are not recommended. Of course the practicality of this method of protection depends upon the size and number of trees and access to electricity.
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Sprinkling the tree with water throughout the freezing period can also protect the blossoms. Sprinklers should be started before the temperature drops to freezing to be sure ice does not  block the garden hose or water line. Continue until the temperature warms. With this protection method, there is the potential of creating an ice storm. If temperatures remain below freezing for several hours, ice will accumulate on the branches and limbs. The weight from the ice may cause branches and limbs to break causing severe, and possibly permanent, damage to the tree structure. Also, if water drainage from the soil is slow and the water displaces oxygen from the roots, damage to trees may result. (Ward Upham)