Fruit growers often wonder at what temperature fruit buds are killed. Many of our peaches and some of the apricots had buds killed by the extreme cold we had on December 18 (-10 degrees in Manhattan). The trees were not hurt but there was no bloom this spring.
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. (Ward Upham)
Apple
Stage 10% Kill (°F) 90% Kill (°F)
Silver tip 15 2
Green tip 18 10
Half-inch green 23 15
Tight cluster 27 21
Pink 28 25
Bloom 28 25
Petal fall 28 25
Fruit set 28 25
Pear
Stage 10% Kill (°F) 90% Kill (°F)
Swollen bud 15 1
Bud burst 20 7
Green cluster 26 15
White bud 26 22
Bloom 28 23
Petal fall 28 24
Fruit set 28 24
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
Tart Cherry
Stage 10% Kill (°F) 90% Kill (°F)
Bud burst 17 5
Green tip 25 14
Tight cluster 26 17
Swollen bud 27 24
Bloom 28 25
Petal fall 28 25
Fruit set 28 25
Plum and Prune
Stage 10% Kill (°F) 90% Kill (°F)
Swollen bud 14 1
Bud burst 18 3
Green cluster 26 16
White bud 26 21
Bloom 27 23
Petal fall 28 23
Fruit set 28 25
Apricot
Stage 10% Kill (°F) 90% Kill (°F)
First white 2 14
First Bloom 25 19
Full Bloom 27 22
In the Shuck 27 24
Green Fruit 28 25
