Hello, Dr. Hill,
I have an Helianthus from the fall line area, a country road ditch with a lot of clay and in full sun. I was given 2 to grow for identification, only possible with your assistance, of course. The mature leaves are quite broad with large teeth, but young leaves not on the main stem start out life with periodic tiny points. Main stems seem smooth, but other parts slightly fuzzy, including leaves (which are opposite, but the way). Flower photos are from Sept. 16 of last year. Thanks in advance.
this is probably Helianthus decapetalus, but I really cannot be certain without having the plant in hand and using a key to identification. It is easier to say what it isn’t than to say what it is.
Dr. Steven Hill, Botanist, SCNPS