Photo: Openverse You can grow sweet tomatoes in pots on your sunny deck, porch, or patio with simple steps. Choose a five gallon container with bottom drainage, set it in eight hours of direct sun, and water once daily to keep the soil moist. Planting your tomato deep in rich potting soil produces strong roots and heavy harvests all summer long. What pot size do you need for growing tomatoes in pots? Every single tomato plant needs its own heavy pot that holds at least five gallons of soil. The container must measure twelve to fourteen inches deep and at least twelve inches across the top rim. Plastic buckets, terracotta pots, or fabric grow bags work well as long as they have several drainage holes in the base. Water must drain out freely so roots do not rot in stagnant mud. Buy a high quality potting mix made for outdoor containers rather than cheap garden soil. Garden soil from your yard packs down tight in a pot, which stops air and water from moving to the roots. Mix three ...