Here's a few comparison pics of my hardy gardenia test I started last year. None of these had any special protection and were exposed to -1F before being buried in snow. Looking at them after removing the snow in March, I would have guessed they were all completely dead. I was very surprised that of the 7 varieties I started with, 5 of them are still alive, only the hardy Gardenia from Logee's and Summer Snow did not return. The results for Summer Snow were somewhat surprising, as it was tied with Grif's select for having the most cold tolerant leaves.
1-5-2015 (before the cold and snow):
9-19-15 (now about 1/4 the size before winter)
9-19-15 (now about 1/3 the size before winter)
9-19-15 (just hanging on)
9-19-15 (about 1/2 the size of before winter, first to start growing in spring)
9-19-15 (about 1/3 the size of before winter)
My Fatsia japonica also did surprisingly well. It is currently about the same size as before the cold and snow last winter.
10-8-14 (before winter)
4-12-15 Looking a bit beat up... most of damage appears to be mechanical due to being crushed under ~5 ft of snow for nearly 2 months, but there was also some dieback on the main stems/trunk. Nearly all of the leaves here would eventually fall off as they were replaced by new growth.
9-29-15 Looking good now.