You don't say what zone you are in, or how much moisture you get...

Some mints can survive in dry soil after they establish themselves, but you know you will have to water them for awhile.

If the gravel driveway gets much traffic they may stay on your side of the driveway; I would be more concerned about their spreading into your flower garden. Again, it partly depends on the vigor of the plants you already have in there, and how much they are able to shade out any mint that tries to grow in their direction...as well, of course, as to how deep any barrier is that you place between the mint ond the garden.

It also depends partly on how vigorous the mint you purchased is. I have had difficulty getting chocolate mint established, especially in dry places, but most peppermint and spearmint mints do better, as long as they have sufficient humus and watering initially.

The height of your mint will be a factor, too, in whether your flowers get shaded out by it. You will still have some hand trimming to do.

If the mint does well, you should be ok eventually, as far as coverage goes. Could you easily reseed with grass if you had to?

Sorry, Zone 5 :)
Very rich clay-like soil. I bought regular spearmint and peppermint plants. The flower beds are bleeding hearts, hostas and peonies along with ornamental onions. I will try and remember to take a photo when I get home today.

thanks!

Do you plan to eat the mint?

I read that it is no good to eat things grown by the road...then my local Master Gardeners told me any edible plants should be grown at least 15, preferably 20 feet from a road.

Just something to consider.

If the patch is near a quiet suburban road, I'd eat the mint without qualms. A problem of pollution only arises when there's a constant large volume of traffic and emissions. Even then, in any city, no matter how far your garden is from the road, you are surrounded by pollution everywhere. There is no line which divided 'polluted air' and 'non-polluted air'. Yet people in cities have edible gardens, and they live (hale and hearty!) to tell the tale.

It could well spread and take over your yard. Why not grow it in a container? A good sized planter would fit in your 2 by 4 foot space. Prop the planter on a couple of 4 by 4s or bricks to keep the roots from growing through the drainage holes.

here are photos of the space....

I might still try containers after all.

If you love mint I'd certainly give it a try. Do bear in mind that it can be VERY invasive! It's probably tougher than you realize. It thrives in New England with nobody tending it, so it can take cold winters and come back. It's considered almost a weed down here in Savannah, so we keep it in pots. I love the stuff, so I've got it in a hanging basket, praying that it never reaches the ground, because then I couldn't keep up with it! (The oregano patch is hard enough to control...) Have you considered oregano?!

On the subject of edibles near a road - I just want to mention I think the problem is not so much polluted air, as it is road runoff. That said, I agree if it is a low-traffic road you're probably ok.

Also, this might be something to keep in mind - I planted two kinds of mint right in the ground in an out of the way area in my yard. This year it grew back pretty much everywhere several feet in all directions, *except* where I originally planted it. So if you want it to actually stay in the 2x4 bed, you might be better off with containers.

from the looks of the pic, street runoff wouldn't be a problem, since the patch is uphill. I grow mint in several raised beds, and, while it is aggressive, I haven't had any problems. Besides, if you don't grow it, how will you have fresh mint for iced tea, mojitos and other necessities of life?

Maybe sink a plastic bed-border strip between the patch and the perennial bed next to it to discourage creeping.

I say try it out! If it turns out that you cannot control the growth of it, then you can always just take it all out. If you try it and it works fine, then you will not have any regrets =)