Wind Shake Plus Wind Chill Equals Trouble
"The freezing point of stems and large roots is approximately 28° or 29° F. We have found that water will flow through stems that are held at 29° to 30° F as long as the stems do not freeze. If the plant is not shaken, it is possible to lower the stem temperature to about 25° F without freezing, and water continues to move up the stem. If the plant is shaken by wind as the temperature falls, freezing takes place at near 28° to 29° F." John R. Havis, "Winter Desiccation Injury of Rhododendrons". The complete and interesting article is in the January 1969 issue of the Bulletin.