Florida is sub-tropical, as is most of the southeast, north through South Carolina and then west across the Mississippi and on across to the west coast (bypassing the hot southwest and Death Valley). Here in Florida, when there's no drought, and the rains are plentiful enough, the heat and humidity combine with ample rains to allow all sorts of ferns to grow, both on the ground and up in the trees.
And even when there are unusually dry conditions all it takes is a relatively small amount of rain in the form of afternoon thundershowers over a period of a week for the ferns to start to flourish. Considering all the invasive species we've introduced in Florida over the centuries, I have no idea of these ferns are native or not. But they are beautiful, and easily spotted just walking around at lunch.
Taken with an Olympus E-P2 with a Zuiko Digital 50mm 1:2 4/3rds lens and DMW-MA1 adapter. Post processed in Lightroom 3.4.1.