18x20 is suitable for tomatoes, peppers and eggplant. I plant in such 3 season. In order to "breathe" you need to leave a short distance between the bags, I put the bags of seedlings in the pallets, watering through the pallet. Very convenient, do not need to water each plant separately. Of the minuses,- 1. they do not decompose. At the end of the season, the bag is easily removed from the roots and disposed of. 2. moisture evaporates quickly, the adult plant needs to be watered more often. 3. if put tightly together, suffocate and begin to "bloom". It's cool, I recommend you try it. Good luck!! The seller Thank you.