I love the" grow bags" and use them in all sizes (also std. pots) for growing just about anything over the years. 20 gallons is huge and requires a lot of materials, but are great for growing large plants or mini gardens. I usually grow full season indeterminate tomatoes/eggplants in 10 to 15 gallon bags/pots, herbs, chives, lettuces, radishes, green onions, flowers, peppers, pea pods, etc., etc. in 2 gallon to 7 gallon containers. The 20 gallon bags easily handle three jalapenos, with cilantro at their feet, when we have cool weather, around the edges! I usually use a concrete wire cage around large bags rather than stakes inside the container, so that heavy foliage is supported in higher winds. In hot dry conditions, mulch around the bags and supply water daily, if needed. A tall Indeterminate tomato in the center or one side or supported cucumber, surrounded by whatever else, is typical for me, as is one 20 gallon wide style bag filled with everbearing strawberries right now that is full of berries this year. A squash or melon may be planted on the side of a well established taller plant or vine and allowed to tumble down the side and across the ground. A variety of peppers have done well ,also zucchini and lettuces , carrots, etc.. I do the containers despite having several large raised beds and 3 garden plots from 30 x 30 , 35 x 40 and 60 x 160 ft., that I currently am working(more is now fallow or abandoned by me). The bags are available from commercial suppliers online at decent prices in bundles of 10, 25, 50 usually, at a much lower price, rather than buying them individually from seed companies and garden centers. I have used the bags commercially, starting about 30 plus years ago, for growing certain shrubs/trees in the nursery. Field grown tomatoes still produce better and resist heat better on the average, but the bagged ones are not far behind and they can be located just about anywhere, with a tray and a little attention, inside a sunny room or under a grow light, as I do with tropical plants. The soilless mix, homemade compost, worm castings/compost, carefully mixed to include trace elements, fungi and ph balanced is critical to success. The perlite and vermiculite are important for best long term results in container garden mixes as well. Besides being lighter, the air and drainage provide healthier conditions, when done at the proper rates for your intended crops likes. Improved yields and flavor follow the attention you give the growing media. Gardeners love nurturing life and witnessing the wonders of plants. We all may have different circumstances or finances, but gardeners will find a way to grow things, if at all possible!
