Very heavy frosts

Although my area is yet to have any significant snow fall, there has been an extreme drop in temperatures, well below zero. I looked out this morning to see everywhere white again with frost and ice. When I went out to look at some of my larger deciduous trees which are still outside, I found bare branches and twigs literally covered in frost and frozen solid. This is a bit worrying, and I am expecting severe die-back of the areas if the trees survive at all untill next year. I have made some more space in the unheated greenhouse and managed to move a large maple of mine inside. The trees in the greenhouse appear to be staying just above freezing point, and I am continuing to monitor their watering needs.