re: Citrus trees and the cold....

Wrap the base on bigger trees. As long as it doesn't split, losing a few (or even many) branches shouldn't kill it.

I just pile up mulch as high as I can. Navel, satsuma, louisiana sweet, and Persian lime survived this way in Jan. of 2010 when it was below freezing for 9 nights here. The lime was hardest hit but fine a year later.