I decided to box up a 6x10' section of my garden and heat it to 40 degrees for last winter. Things didn't go so well.
Bougainvillea 'Bengal Orange' - dead
Red Abyssinian Banana - dead
Blue Java Banana - dead
Castor Beans - dead
Acalypha - dead
Thailand giant elephant ear - dead
Gardenia - alive, but defoliated by mites
Trachelospermum jasminoides - alive and well
No idea what happened. I haven't dug them up yet so maybe I'll find underground rodent damage.
Misc: hard to believe that if I had covered the windmill palm for that night of -16 two winters ago, it would have sailed through this winter with ease too.