Helianthus divaricatus, H. strumosus, and H. hirsutus
I am more of a gardener these days than a botanist but still love trying to identify plants. I worked at the FSU herbarium for a couple of years -- first, as an assistant to Loran Anderson who had just been hired to teach and be the new curator; and second, as a botanical illustrator for him, Andy Clewell, and R.K. Godfrey.
I grow a Helianthus in my yard that was a roadside sunflower from Leon County. These are, as you say, "all over the place". I too have puzzled over the identification. I worked on it again this summer and came up with H. hirsutus. This was based on the stems being more scabrous than not so and the leaves subsessile. H. strumosus leaves have some petiole and the stems are not scabrous. H. divaricatus has not been collected in Leon County according to florida.plantatlas.usf.edu which seems peculiar for such a common sunflower here. That means to me that the consensus among botanists is that our sunflower is not H. divaricatus. So I am calling yours, which looks very much like mine, the same.
I put out an email sometimes weekly on my garden which is a mixture of natives and non-native species. It you would like to see it, contact me at melanie.darst@icloud.com.
