What you see above are refill packets we buy from the stores, usually food related. Since they are of good material, I use them mostly to start new seeds or keep small plants in temporary states. They are very handy. I cut or punch out a few holes in the bottom for drainage. In the picture above, last year I tried to grow extra mint cuttings. I tried this method by keeping them together. Initially they showed good signs but it did not work. I felt it required more nutrition. They did poorly.
As an experiment I had kept shallow trays at the bottom, which are the remaining bottoms of broken buckets! I wanted to see if that self-watering [by capillary action of the soil itself] worked for this. I had it in semi-shade. This avoided regular watering. When it rained heavily I drained out the water in the trays. I think it was too much water that did not help.
Dinu, That is what I was wondering. Maybe the drainage wasn't enough. In the NE US, mint grows wild almost anywhere, but particularly loves growing beside stream beds where there is lots of moisture, but it is well drained. Good luck with you next experiment. Always good to experiment!