Mine just multiply in place and don't ever spread beyond their border so they just look fuller each year. Never had them send up even one daylily in the lawn area (really lots of weeds that I keep mowed). I had common milkweed that did what you describe, sending runners out even 15' away from the main plants. I dug those up and moved them behind the garage where they could over run that area and I'd be happy. And so would the monarchs.
