Stage of growth is critical when we have spring frosts and freezes as well as the temperature and length of time at that temperature.
Apple flower buds are classified by stages, beginning with dormant (winter) to silver tip (when the bud turns from brown to a silver color) to green tip (a touch of green tissue showing) and other stages, ending with post bloom or blossom drop.
Apple flower buds that are at silver tip can withstand 16F for up to 30 minutes with no damage. However, at 15F for up to 30 minutes there will be 10% bud kill and at 2F for 30 minutes, there will be 90% bud kill.
Michigan State University Extension has a great handout that lists the critical spring temperatures for tree fruit bud development stages. The list includes a complete list of tree fruits. Growers rely on this information to determine their options for protection.
If you have peaches and apples, you can check unopened buds to see if they were damaged. Cut the flower bud in half and if the center is brown, the flower was killed by the cold temperatures.
If you had herbaceous (soft green tissue) plants injured such as perennials, cut them dead out or cut them back to the crown of the plant. This encourages new growth.
It’s likely we will have another frost or even freeze yet this spring. If predicted, there are a few things you can do to help protect plants.
Irrigation can be used to help prevent damage to flowers and foliage, particularly fruit crops such as strawberries, apple, peaches, etc. Keep in mind that the flowers are the most sensitive part of the plant and if damaged, there will be no fruit that season.
Overhead irrigation should be started as temperatures drop to around 34F. The water freezes and as it changes to ice, it releases heat. Water should remain on until the ice is completely melted.
Overhead irrigation is risky and should be researched thoroughly before using, particularly if you are growing a large commercial crop. It must be used correctly and there is a lot of room for mistakes.
Row covers, blankets, burlap, sheets, or other lightweight fabric can also be used to cover plants. Do not use plastic as it doesn’t trap radiant heat from the ground. In addition, leaves can freeze if they touch the plastic.
Remove frost protection covers in the morning as the sun comes out.
Keep in mind, cloudy windy nights are great as these don’t allow frost to settle. And, we can have frost when temperatures are in the mid-30′s if the night is crystal clear and calm.
And remember, if there is frost or freeze damage this year, there is always next year!
Credit: Contributed
Credit: Contributed
Pamela Corle-Bennett is the state master gardener volunteer coordinator and horticulture educator for Ohio State University Extension. Contact her by email at bennett.27@osu.edu.
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