Shotweed (Cardamine oligosperma)
I'm losing a battle with this weed. I have to pull gobs of it every Spring - filled a 5gl. bucket this afternoon with the stuff and that was just between the stones in the courtyard. There are still bunches of it growing in my flower beds, sometimes right smack dab in the middle of a flower -my anemones for instance. And like I say, I pull every year.
I know to try and yank it before the flower heads turn to seed, but what a chore. I never just throw them on the brush pile either, I put them in a garbage bag.