I agree with the person on the other thread who said it's burdock. Probably common burdock, Arctium minus. It's on the Colorado "C List" of noxious and invasive plants. The C List are plants that you're not required to get rid of---but you probably want to! Burdock has DEEP tap roots which can apparently be eaten the first year. You're past that! If you decide you want to get rid of them, my best advice is to cut the bottom out of a trash bag big enough to encase an entire plant, pull the bag over the plant and be sure all the leaves are inside, anchor the bottom of the bag securely to the soil with bricks or something, carefully spray the leaves inside of the bag with roundup, then fold the top of the bag down over the leaves and let it stew in the sun! I've done this with thistles in my perennial bed, and it seems to work pretty well. Don't remove the bag till you're absolutely, positively sure the plant is dead! If you try to dig it out, and any root is left in the ground, it will very likely come back and you'll just have to keep fighting it.

Pictures in the link below. Not sure, but I think you'll need to scroll down about a third of the way on the page to get to the 3 burdock pictures. They're right underneath the purple flowered thistles! (Just tried it, and the page comes up just above the burdock, at the bottom of the thistles!)

Good luck,
Skybird

P.S. Welcome to RMG! If you have time, go over to the Who's Here in 2009 thread and tell us a little bit about yourself. We're glad you found us!