I have visited several large display gardens in Georgia and they are about equally split between those that grow in some shade and those in full sun. Maybe more use of shade in South Georgia than in north Georgia. Tim Bell's garden in South Georgia has tall pines as well as some lower trees, but he also has beds outside the main "showplace" garden, some covered and some not. Bill Waldrop just north of Atlanta is out in the open although he has a big greenhouse too. I have not been to gardens in Florida, but I think I have read that most of the big hybridizers use shade cloth over their hybridizing areas or have greenhouses in which they hybridize.
Larry
