Frozen Fruit Blossoms
Posted: April 18, 2016
Recent temperatures down around 20 degrees or colder have certainly been cause for concern. To fully understand what is currently happening from the plants’ perspective, we have to go back to the mild winter. The winter was good for fruiting plants. We did not have extreme low temperatures. It takes temperatures around fifteen below zero to damage fruit buds when they are dormant. Once the temperatures start to warm up and the plants break dormancy the temperature at which the fruit buds are damaged increases significantly. The problem is that the warm March started the fruit bud development early, too early.
Other factors also influence freeze damage to fruit buds. There are differences between varieties. There are differences between the different buds on the same tree. Plus there are differences between young and old trees. Fruit buds on older trees seem to take a freeze better than buds on a young tree. Finally, there are differences between sites. If the fruit is growing on a northern slope it will not be as developed as fruit on a southern slope.
So, can you expect to have fruit this summer? Let’s discuss this by crop. You can expect about 10% fruit bud loss if the temperature gets down to 27 degrees at the stage most apple trees are currently at in the region. You can expect 90% loss if the temperature goes down to 21 degrees. The temperature at which death occurs will continue to increase until the blossoms are open. When the blossoms are open, 10% death occurs when temperatures get down to 28 degrees and 90% death occurs at 25 degrees. Considering the current state of development of peach fruit buds, 10% death occurs at 25 degrees and 90% death occurs at 15 degrees. The current numbers for pears is 10 % death occurs at 20 degrees and 90% death occurs at 6 degrees. Sweet cherry numbers currently are 10% death occurs at 26 degrees and 90% death occurs at 17 degrees.
Strawberry blossoms did not develop as quickly back in March because the straw covering them provided some insulation. So far, the strawberry buds are still alive. The exception is if you are growing strawberries on black plastic. Those plants were more developed when the low temperatures arrived, so some of those flower buds have been killed.
Blueberry flower buds are probably still alive. It depends on how cold it got at your site. Again, at the current stage of development some bud death will occur at temperatures below twenty degrees.
There has been a great deal of variation in low temperatures throughout the region over the last few weeks. There is still the possibility of low temperatures during bloom. We will not know with certainty if we will have a fruit this summer, but let’s be hopeful.
For more information contact your local extension office. In Lackawanna County call 570-963-6842 or email LackawannaMG@psu.edu.