But then the more work I do looking these up, the more I read; this resembles that, this looks exactly like that, these two can't be separated, these hybridize, the genus and species need revised, etc. Okay, now I don't feel so bad, so on with it.
PLANTS WITH OPPOSITE LEAVES (for the most part). What? Didn't he say for the most part once before? Yep, just covering my butt. Some are both alternate and opposite. Now you see why a key isn't easy.
Plant with opposite leaves that reach around and form a cup (perfoliate)
Cup Plant, Silphium perfoliatum
Leaves mostly basal, elongate, entire or weakly toothed, rays distinctly notched or lobed.
Lance-leaved Coreopsis, Coreopsis lanceolata
Leaves always in 3's.... Always? Really? Yippie! (well, the majority of the plant, but not always), darn
Tall Coreopsis, Coreopsis tripteris
Leaflets 5-7 or more....Bidens polylepis, Beggar-ticks, Spanish Needles, Stick-tight
Bidens aritosa has fewer bracts, but otherwise can't be separated, and some authors simply lump the two. Hey now, there's an idea.
Leaves paired...coming up
Leaves whorled...Whorled Rosinweed, Silphium asteriscus var. trifoliatum
Plants without stalked leaves, or at least appearing so. (That means don't go up to it with a hand lens to check, just make a general observation).
Stem smooth or rough...coming up
Stem AND leaves covered in SOFT velvety hairs...Downy Sunflower, Helianthus mollis
Plant smooth or rough, not downy soft.
Leaves VERY long and narrow, barely an inch wide, many times longer than wide. Saw-toothed Sunflower, Helianthus grosseratus
Leaves shorter, wider, a few times wider than long. Too vague? keep going.
Only now are we getting to the ones that look alike. Huh?
In the sunflowers, the center head is where the reproductive portions are housed. In ox-eye, the rays themselves are fertile. You can't see that unless you pull off a ray.
Well there it is. An attempt at least to work with a difficult group of plants. I don't know how accurate I've been, and it will take an expert to hopefully straighten me out someday. If any are misidentified, and that bothers you, well you can go to helianthus.