I have only heard of two FL heirloom plants. One is the Seminole Pumpkin that pre-dates the turn of the century. There is a lot of info. on how the indians grew this up in trees. The second is the Heritage Sweet White Onion. I don't know what part of the state this was found growing or how far it dates back. The website said that it was found growing on an old Florida homestead. I'm sure that there are lots more.

Maybe you can find out more from some old tourist sites. The author Marjorie Kinnen Rawlings (spelling?) had an old FL home in Gainseville area. She has a cookbook out. Perhaps there is some mention of what she grew in her garden.

I hope this helps.