What happened to our plants in our February, 2011 “Arctic Freeze’
In our desert climate, we do not have cooling temperatures during the winter that put our woody plants (trees and shrubs) into a true state of dormancy. When a plant does go into full dormancy, it develops freeze tolerance. Just as we are not very tolerant of freezing temperatures, nor can our plants be tolerant!
As our temperatures drop well below freezing and stay low for a period of time as they did in February, ice crystals form inside the cells. These intracellular ice crystals rupture cell membranes, resulting in leakage of the cell contents. Thus, tissues injured by low temperatures often appear water-soaked and are flaccid.
The Relationship between a Full Moon and a Frost – not science-based proof!
1. If a warm air mass is on top of us, it holds the heat in and we typically will not get a frost.
2. The heat of the sun is reflected by the moon.
3. Frosts are more likely the closer we are to a full moon, because the heat reflected by a full or nearly full moon is enough to evaporate the water in the upper atmosphere that otherwise would have reflected the sun’s heat back to earth. When the water evaporates, heat escapes and the air gets colder.
However, many of those on the Internet that have looked at this issue are known to say, when it's clear you're more likely to see them.
And now that you are getting around to reading this, I expect the danger of any substantial frost or freezing in the Tucson area is over. Before you know it, we will be talking about how hot it is!!!
Use our Master Gardner program through the UA Cooperative Education program for your plant information. 
