Hi, Crazy: Welcome to the Minter's Remorse Club, although it does sound to us as though you still retain some measure of sanity -- which you will need. A lot depends on how big an area you are talking about. Unfortunately, flower gardens are especially difficult to fumintigate (we just made that word up, so don't go looking for it). Short of just pulling everything up, the way to start is around the edges of your plot, or even around edges of specific mint colonies beyond which you are sure that it has not spread. Start killing all the way around the edge. You can apply boiling water; or a 5:5:2 mixture of vinegar:water:dish soap; or even newspapers or flagstones to block light. Give it a day, then start pulling up, being as careful as possible to get everything. The problem is the rhizomes, which spread laterally and look like white shoelaces or pieces of spaghetti. You need to get every bit. When you start your next session farther inside your perimeter, recheck where you did before, clawing up the soil again to make sure you didn't miss anything. Work your way inward in each area. It's a long, long process, but you certainly get to know your garden well! Good luck!
Hi, Crazy: Welcome to the Minter's Remorse Club, although it does sound to us as though you still retain some measure of sanity -- which you will need. A lot depends on how big an area you are talking about. Unfortunately, flower gardens are especially difficult to fumintigate (we just made that word up, so don't go looking for it). Short of just pulling everything up, the way to start is around the edges of your plot, or even around edges of specific mint colonies beyond which you are sure that it has not spread. Start killing all the way around the edge. You can apply boiling water; or a 5:5:2 mixture of vinegar:water:dish soap; or even newspapers or flagstones to block light. Give it a day, then start pulling up, being as careful as possible to get everything. The problem is the rhizomes, which spread laterally and look like white shoelaces or pieces of spaghetti. You need to get every bit. When you start your next session farther inside your perimeter, recheck where you did before, clawing up the soil again to make sure you didn't miss anything. Work your way inward in each area. It's a long, long process, but you certainly get to know your garden well! Good luck!