The mild winter and last week’s warm temperatures have pushed many perennial fruit crops ahead of schedule this spring, and the recent cold weather has many of us thinking about possible freeze damage to fruit buds.
Michigan State University compiled quite a nice poster showing the various stages of development of several tree fruit crops, and gives critical temperatures for each. I find this pretty useful:
The following article from Penn State not only gives a lot of information about frost and freeze protection, but also about small fruit bud (strawberry and blueberry) critical temperatures:
One additional point for blueberry growers – cold temperatures have been shown to predispose blueberries to mummyberry infections, so it may be particularly important to monitor for the emergence of apothecia, and to apply fungicides in a timely manner.
Were buds killed? I do not yet have information from around the state, but the temperatures we hit on Monday night in some areas were certainly cold enough to damage some crops. If freeze damage occurs, it may take several days before dead tissue is evident. To determine whether buds are injured, hold buds at room temperature or cooler for 4-6 days, and then cut open to examine for browned tissue. For open flowers, blackened pistils and/or ovaries will be evident within a few days after the cold event.
Although the cool temperature we’re experiencing now are slowing things down somewhat, we are not yet out of the woods… we can all keep fingers crossed for moderate weather, and no more cold snaps.
For more information: www.extension.unh.edu