I am 25 and both me and my father had grown tropcials in KY for years. We have thought up crazy ideas to grow tropicals outside. Even as I type I can see crazy looking tents over palms in our front yard LOL. But last year while on a trip to mammoth cave the tour guide said something that no one else seemed to hear or care about. The tour was in the summer so was about 90 to 100f outside. As we walked to the cave it got very cold. The tour guide said the air around the cave stayed at 55f. The air coming out of the cave in the winter was very warm at 55f in the summer cool at 55.

So at the mouth of this cave you could grow just about any tropical with no porblem. Now most cave places I know of are parks and adding plants is always seemed to be a problem as they are only interested in native. But if anyone out their knows of a similar situation this should be tried and if so I would love to hear about it and see pics. THANKS