At 7 this morning it was around 18 degrees (f) and the rhododendron leaves were curled as tightly as pencils.
Here is how I know that nature knows more than we do: in very cold dry weather the rhododendrons know that they need to conserve moisture; so they very mysteriously(without benefit of a thermometer) begin to close the stomata on the undersides of their leaves through which moisture is released. Closing the stomata reduces the surface area on the lower part of the leaf, causing the leaf to curl. The thin leaf tubes also offer less wind resistance, thereby making the plant less likely to be damaged by gusts of wind. (The three scarves are examples of a beautiful, although less elegant, way humans try to stay warm.)
So here's a bonus photo that P composed and took after seeing the apple pie I just pulled out of the oven: The Jesus Brothers Go To Sea.