The cold arctic airmass that moved through this weekend ended up causing some significant damage to blooms and developing fruit on blueberries. Dr. Donna Marshall of the USDA-ARS in Poplarville shared some plant tissue with me to evaluate, so I took some photos.
As you can see in the above photo, browning of the bloom tissue is an indication of freeze damage. Any blooms that were open will result in damage. The cold air was able to penetrate into the corolla to damage the reproductive organs thus rendering it untenable. The good news is that unopened flowers are likely to produce fruit.
Browning of the corolla is not necessarily a death knell for the flower — if it was closed. The flower petal is not the crucial tissue, but rather the reproductive organs — stigma, style, ovary, pistil, anthers, etc.
There were some unfortunate aspects to this freeze event — the winter had been very mild and bloom was earlier than normal. The cold event was a large airmass and not a radiation-type event, so there was not a lot of freeze protection that could be done. Southern highbush varieties, which typically bloom earlier than rabbiteyes, will be hit the hardest.