I started Cardoon from seed last spring. I didn't have a long enough season for it to bloom, but it was still an amazingly cool plant! It lasted through several freezes before finally going flat.
Here it is with my favorite "no care" plant of last year....Melampodium.
Rosa 'Cinco de Mayo' also seems to need no care. I don't even deadhead it, and it continues to bloom non-stop until almost November in zone 5.
...and, year after year.....salvia 'Victoria Blue'. It's supposed to be an annual here, but has been coming back for the last two on its own.