I was talking to my neighbors, he suggested California poppies. He has some
planted in his side yard, they're incredibly hardy and love the full sun.
Plus they spead out and take over in horrible conditions.

Yeah, that's a good idea. I don't know if Seattle is part of their
native range, but parts of Washington state are, so if not you are
close.

People usually grow them from seed.

As for "horrible conditions", I've even grown them in pots (although
they weren't very happy). I don't have any firsthand experience
growing them outdoors.