From Spokane Wa here.. I just discovered this Northern Forum. Seems I'm always late or the last to the party. About your Elms, did you find a solution? I have basically the same problem with my Elms, they sprout like weeds everywhere. If yours are anything like mine you find that you can pull some out and they come up with roots and others you can pull and pull and pull only to discover they are offshoots of a major root from some mature tree. I sprayed a couple of these with brush killer before I knew they weren't on their own root systems. The offshoots did die but the brush killer also affected the Mother tree, which in some cases was 50 or better feet away from the off shoot. Since I don't care to have a massive die off all at once of the mature trees I've stopped spraying all together. So now I pull or weed wack or mow them down. So if you have found any long term solution I would so love to hear it.