Erigeron strigosus
Asteraceae
Four species* of fleabane can be found along the Potomac River in the Piedmont. They’re all pretty similar looking – terminal clusters of many-rayed (50-100) composite flowers, with yellow discs; the rays can be white, pinkish, or purplish. The plants can be distinguished by leaves – how they’re shaped, whether or not they’re toothed – and by a few other characteristics. They range from a foot tall (Robin’s plantain) to five feet tall (lesser daisy fleabane).
Sadly, I don’t have photos to illustrate all this. Maybe next year I’ll get some. Mostly I just wanted an excuse to publish the above photo, because I really like it.
*Erigeron annuus, E. philadelphicus, E. pulchellus, E. strigosus
Elizabeth's Wildflower Blog 
And a lovely photo it is! I think the fleabane I saw most often this spring along Billy Goat B was E. philadelphicus, and every single time I saw it, I would sing (in my head) “PHIL-A-DELPHIA FLEABANE!” to the tune of Elton John, involuntarily, and be stuck with it the rest of the day. Maybe next year I’ll pay more attention to details and identify the rest of the fleabanes.
Ha! There’s an area I call “trout lily hill”, and when they’re blooming I sing “I found my thrill…” (to the tune of Blueberry Hill). I think there are other song associations, can’t remember them just now. Anyway, E. philadelphicus and E.annuus are both pretty common; if I’m remembering correctly, E. philadelphicus is first to bloom, then E. annuus, then E. strigosus. E. pulchellus seems to be much less common in that area; I’ve found it along the towpath in a few spots. It tends to get mown over, though.