Fruit growers in central Kansas often wonder at what temperature fruit buds are killed. 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.
| Apple | 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 | 15 |
| Petal fall | 28 | 25 |
| Fruit set | 28 | 25 |
| Pear | 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 | 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 | 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 | 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 | 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 |
To determine whether a fruit bud is alive or dead, use a sharp knife or a single edge razor blade and cut buds in half. Remove buds from the tree and make the cut starting at the base and cutting upward.
If the fruit pistil (see image) in the center is greenish white to cream color, no damage has been done. However, if the fruit pistil is dark brown or black, it has been killed. Cut a number of buds to find a percentage killed. Some loss of buds is actually beneficial for peaches and apples. These trees often produce far too much fruit and require thinning for top quality. As a rule, we want an apple or peach an average of every six to eight inches on a branch. We can often achieve this with only 10% of the original buds developing fruit.
It is possible to give some protection to fruit blossoms from freezing by covering the tree with a bed spread, blanket or similar fabric. Old-fashioned Christmas lights distributed around the tree will help to give additional 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.
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