2. Black-eyed Susan
3. Rose of Sharon, Althea
Growing up we saw Potentilla fruticosa with yellow flowers. A few years ago while planting a white garden we found the cultivar "Abbotswood" which has white flowers:
It's become our potentilla of choice whenever we plant potentillas. And we like to plant them, since they bloom all summer long, and are generally a reliable plant.
When we lived in New Hampshire a nursery worker commented that they treated them as a perennial up there, figuring on total dieback in the winter and revival in the spring. I don't know if that's really true -- perhaps just that person's view on things. Around here we have the delicate outline of the branches all winter long.
I had forgotten that potentillas are also known as shrubby cinquefoil, which strikes me as a case where the common name is more complicated than the Latin. I vaguely remember hearing them called Tundra Rose, but Widdy? Really? The Wikipedia article I linked claims they're called that. Umm, yeah, and sometimes we call them "potentates" just to be silly, but I don't think I'd be writing up an article claiming that name. So I looked up "widdy" (following the rabbit trail), and discovered it is a rope made from flexible twigs such as birch; also, a hangman's noose. Hmmm, okay, potentilla branches are thin and flexible; if I squint I can see it.
I may start using that name, just because I think it's a fun word to say. Widdy widdy widdy.
More info about the 100 Species Challenge here; link in the sidebar to all of my 100 Species Posts so far.