I love it too!!! I planted all sorts of mint in pots last year, so I could contain it. I cut them all back at the end of the season last year. They were neglected all winter, just little wiry sticks. For all intents and purposes, looking dead.
This year, I needed the containers for new herbs. I took out the old mint, which was showing signs of green, not much, but it was there. And I took a shovel and cut about 3 inches down all around, making a disc (amazing root structure). I took the discs (spearmint, peppermint, lime mint, chocolate mint) and planted them in a bed devoted especially for them. I didn't really expect them to do a whole lot. I planted a round disc here, and round disc there. SURPRISE!

Today they are thriving. It wacked their little heads off when they got about 1 1/2 feet tall, and now it's all bushing out. It's a field of mint...it's lush and I love it. I'll never use all of it, but it's just a lovely part of the garden, near the table outside. A lovely place to sit in the morning among the mint. :-) Great place to take a pot of tea. ;-)

I love spearmint, but I'm not brave enough to put it into the garden. Not after my first attempt, I'm not. That time, I put in barriers one metre deep of solid wood all round it. It not only grew over the top of the barriers, but the roots went right down, across a wide lawn (large enough to play cricket on), across and under a 2-car-wide concrete driveway and into the neighbour's garden. It took a LONG time to get rid of that lot, let me tell you!

Personally, I think mint could break through a concrete bunker intended as an atomic fallout shelter. I think there is NO barrier large enough or strong enough to stop a determined mint from breaking out. I now keep all my mints in pots, and I repot them at least twice a year. And I keep all the pots on concrete, but even then I have to watch it.

I'm kinda grateful... usually with our heat and dryness, I don't get much mint and what I get is ratty looking, but this year we had a nice long spring and I got to have nice looking mint that hasn't been munched to lace. This is a mint I've had for 7 years and FINALLY I actually had to ask a friend "how tall does mint get?" :D

ny mint broke out of its pot and promptly propogated all over the daisy bed. Months and Months later I was still puttling roots. Fortunately I'm pretty stubborn myself.

That being said, it will NOT grow where I want it to out back.

Time to make mojitos!!! :D