I read about this a few times. I'm not sure if this is what you are looking for but I'll tell you what I remember. I heard that in some countries they are using this technique for teaching indigenous people how to garden with minimal water and minimal fertile soil. They claim that these people end up with tiny food gardens right outside their front door when all around them is effectually desert. The basic idea is just to take a plastic bag of compost
(or potting soil
) and open it up, making slits or small squares and place seeds in it. You save water because there is no real drainage and it is just so easy to start. Here, though, I just don't know why you would prefer this over a regular potted plant. I also read that you can do the lasagna thing where you garden this way in order to smother the underlying grass and then after a season, you just empty the bags and you never had to till or kill the grass before beginning a garden. I've never heard of special grow bags, but compost is the best growing medium ever anyway!