If you have limited space or all your outdoor space is paved, you can use grow bags to grow a vegetable garden. Tomatoes (Solanum lycopersicum) need a much larger bag than most vegetables, so use anything from a thick garbage bag, a potting soil bag or a woven plastic feed sack to grow tomatoes. Ideally, the bag should have a capacity of 2 cubic feet to hold enough soil.
Place a crate in a site that receives full sun or six or more hours of sunlight daily. Alternatively, you can poke several holes in the sides and bottom of a 5-gallon bucket or use a plastic laundry basket to support the grow bag. Set the container in place before you add and fill the grow bag so you don't have to move the heavy plant later. If you do need to move the bag because you determine the site isn't right, the crate, bucket or basket supports the sides of the bag to prevent ripping.
Place the bag inside the crate, bucket or basket. Spread the bag open as much as possible so it takes up the available space inside the crate or bucket. You can use almost any type of bag, but avoid using black garbage bags that draw more heat to the plant. In addition to feed sacks and heavy garbage bags, try a large, reusable shopping bag or twist and tie one end of a length of heavy sheet plastic. If you use the original potting soil bag, place the full bag of soil in the container.
Open the top of the bag and fold it down twice to help keep the bag open. Fold the bag from the inside out. Slide paper clips over the folds, if needed, to secure the folds. If using a potting soil bag, use scissors to cut along the top edge of the bag.
Fill the bag with sterile, humus-rich potting mix with good drainage. You can use a bagged potting mix from a garden center or make your own blend, mixing equal parts sphagnum peat moss, finished compost and coarse sand or perlite. Skip this step when using a bag of potting soil as the grow bag. If you wish, remove some of the potting soil and replace it with finished compost to add more nutrients to the mix.
Poke several holes in the sides of the bag using a sharp knife or a punch tool, so excess water can drain from the potting soil. More holes equal better drainage, but too many holes can compromise the bag, so space them about 4 to 6 inches apart and keep the holes small so soil doesn't fall through them.
Hold the top of the bag closed and tip the container on its side. Poke drainage holes in the bottom of the bag spaced about 3 to 4 inches apart. Set the container down and open the bag.
Water the potting soil until water begins to drain through the drainage holes. Wait about one hour for water to drain to the soil at the bottom of the bag and water a second time. Allow several hours or up to one day for the soil to dry out until it is evenly moist, but not soaking wet.
Plant a small tomato transplant in the grow bag to the same depth as its root ball -- the top of the root ball should be even with the top of the soil line in the bag. If you have a tall, leggy transplant, plant one-third to one-half of the stem under the soil's surface to ensure a deep root system and strong plant. Watering is not necessary because the soil is already moist. Water as needed to maintain even moisture.