We've got a situation where there is beach grass growing up to and into a formal lawn. The problem isn't so much the grass popping up into the lawn, it's that the beach grass is getting nutrients and water from the lawn and growing too thick at the boundary. It needs to be edited regularly. We'd like to limit what it can get from the lawn by limiting it's ability to run to where the good stuff is.
The lawn is organically managed with no or very little soluble nitrogen and infrequent waterings.