In Ayrshire, two spells of cold weather seem to have killed mine, it is a brown sorry looking specimen. The first prolonged frost lasted four weeks, including spells that were at least -15C, it seemed to weather that becoming the pale yellow green it did the previous two winters. The second frost was shorter lasting two weeks at probably didn't go much below -10C, and it was during that period that the tree noticeably turned brown.The ground remained frozen between the two episodes and probably to some depth. It took the ground about a fortnight to defrost. In all the tree had to endure about eleven weeks of being frozen. It is too early to tell if the tree is actually dead, it may start growing again, or spring up from its roots. Notably the suddenness of the frost prevented the tree from developing the 'frost caps' that it had during the previous two winters when there were a few days below -12C, but the majority of the frosts were less severe. I intend to leave it in situ until the autumn when I'll have a better idea of whether it actually died or not.