I think I have these growing in my yard in Florida. Well, died down for the winter, but it's locally common in weedy areas. Leaves are quite rough, upper and lower with fine hairs. Petiole is lightly reddened toward the stalk, and the leaf clads the petiole all the way to the stem. Leaf shape is irregular, rhomboid and has some tiny teeth, about 2cm apart. As I recall, the leaves are variable, and get narrower, almost lance shaped near the yellow flowers. The flower petals are folded where they attach to the disk, and when it seeds, they appear as 5mm ovoids at the edge of the disk while there are still petals. It would flower in my late summer. I don't know for sure, but the closest I've come to identifying them is Tithonia. These are common enough for seed vendors to call them Mexican sunflowers, although the petal color ranges from orange to red, sometimes yellow. There is a large Tithonia diversifolia with yellow flowers growing untended within a mile or so, and those leaves are too deeply lobed to be precisely what I have. But Tithonia rotundifolia is almost always pictured as red flowered.
