I think that one night of going below freezing should be ok... I would wrap for the winter though! All 4 of my trees are wrapped in a similar fashion (Italian snowman). All trees were wrapped by end of Thanksgiving weekend.

1.)Mulch (compost around the base of the tree (6-10 inches)
2.)Tie all all branches towards the center of the tree upwards.
3.)Wrap entire tree starting with the trunk in 1 layer of fiberglass insulation.
4.)Wrap insulation with 1 layer of blue tarp.
5.)Complete with a bucket on the top so rain does not enter.

I will see my trees in the Spring (end of March-early April)

Yikes.

It's not really the 14 degrees that's the problem, so much. The problem is that the temperature dropped so quickly -- so the tree didn't have time to adjust to gradually falling temps.

Not all zone 7s are created equal, but in my zone 7 I don't do any protection -- AND all my trees are outdoors in pots -- and they do just fine. If you have a lot of sudden drops like that, though, mulching and wrapping would probably be a good idea. Sudden changes like that are really hard on plants in general!

Thanks for the reassurance and suggestions. It's back to 50degrees and the ground never froze, so I'll keep my fingers crossed, and wrap the tree for the rest of the winter. I don't know what was up with that weather.. it's so rare to ever get that cold, and not that fast.