The short answer? I don't. Mint is only one of a number of uncontrollable plants I have mixing it up in the garden beds here. My approach is to put bullies in close proximity to each other and hope their aggressive tendencies work to keep each other in check. Here, the photo that triggered the comment.
These wildflowers (bluebonnets, pink evening primrose, prairie verbena) and native ground covers (predominantly wood sorrel) all have a tendency to take over for part of a season and then go dormant and/or seed out. They each in turn will fill the empty spots created during the others' dormant spells. All I have to do is keep an eye out for those transitional moments when one plant must yield to the other. At those times I yank and clip fearlessly as needed.
As is often the case here, this riot of competing ground covers wasn't anything I planned in advance. I had open areas I didn't want to spend money on mulching or simply watch helplessly as they filled with weeds, so I "allowed" these aggressive plantings to provide the weed suppression mulch would otherwise. The zietgeist here is very Garden of Least Resistance.
|Their days are numbered|
I think of the oregano as a rock with the purple heart functioning like a wave against it. You can see how the purple heart is both attempting to grow up over and insinuate itself under and through the established oregano.
|I love you, goodbye.|