I want to plant some organic mint seeds. I read that I should put in a 10 inch barrier to keep them from spreading. I can only find a 6 inch polyehylene barrier. Is this adequate? Is polyethylene ok to use in an organic garden?
Thank you.

I've had spearmint in my garden in a buried plastic ice cream tub (with the bottom cut out) for 3 years now. It's probably not more than 6 to 7" across. I do have to watch because it tries to send runners up over the top of the ground to take over more territory. I just whack those off when I notice it. I never gave the plastic a thought, organic-garden-wise. I mean, I ate the ice cream out of it, ya know? Am I being unwise here??

Various plastics can leach into foods and end up being incorporated into your cell membranes where they make a mess of cross membrane transport. Some believe that this is one of the causes of chronic diseases. Therefore I would not plant in a plastic container. Polyvinylchloride and some other soft plastics which are frequently used for food wraps and packaging and are definitely not healthy. My question is whether this extends to polyehylene, which is a simpler chemical.

Perhaps a simpler answer is to put your mint into a planter? That's what I did with mine...then put it on a cement patio...mint is SO invasive! If you're intending on a LOT of mint, then perhaps a defunct bathtub, horse trough, or barrel might work.