Pour the loose gravel into the bottom of the pail. The rocks provide drainage for the soil, keeping the plants from suffering root rot. Fill the pail with potting soil to three inches from the top. Tomatoes need plenty of soil to grow.
Plant the tomato and pepper plants on opposite sides of the 5-gallon pail, giving them room to grow and spread their leaves. Place the stake directly beside the tomato plant and securely tie the plant to the stake with strips of soft cloth.
Plant two or three cucumber seeds along an alternate side of the pail. Imagine the pail being a clock, with the tomato being at 12, the pepper being at 6, and the cucumber seeds being at 3 o'clock. As the cucumber vine grows, it will cascade down the side of the pail, leaving room for the rest of the plants.
Plant two or three onion sets at the 9 o'clock position of the pail. Plant radish seeds and lettuce in between the main plants. Lettuce and radishes come up quickly and are harvested before the other plants. As the vegetables are harvested, more can be planted as long as there is still room.
Water the entire pail once everything is planted, and place in a sunny location. The brighter the exposure the better. These plants do not have the luxury of ample room and sunshine, so the container garden must also be given a quarter-turn once a day so all the plants get even sunlight.
Keep a close eye on when the plants start growing and thin out the cucumbers to one strong plant. Train the cucumber to grow over the side of the pail so it does not conflict with the other plants in the container garden. Water every morning to ensure the tomatoes do not suffer from blossom end rot, a common disease among plants that do not receive the proper amount of water.
Harvest the onions, lettuce and radishes as they mature and replant as desired. Pinch the tomato plant to remove side shoots and keep one main stalk growing. This keeps foliage to a minimum but still leaves enough for the tomato plant to blossom and set fruit.