Containers of many types can be recycled for the purpose as long as they are at least four inches deep and have drainage holes. Most potting soils will work well and usually contain a combination of peat moss and vermiculite or perlite and are designed for use in shallow containers. If the potting soil doesn’t include fertilizer, you can use a liquid fertilizer to get plants going, and a slow-release fertilizer to mix into the potting soil.
To start a salad bowl in the fall, winter, or early spring, you can sow seeds into your containers and grow your own plants. In the spring, it’s often easier and quicker to purchase cell packs of small plants. Lettuce plants are often available with green, red, frilled, and lobed leaves. Other greens that can be included in your salad bowl include arugula, beet greens, buttercrunch lettuce, kale, mizuna (a mild-flavored Chinese mustard), Romaine lettuce, spinach, spicy red mustard, and Swiss chard. Add chives, cilantro, dill, onion, or parsley plants for additional flavors. You can include edible flowers like pansies or Johnny-jump-ups, which have a mild, sweet flavor.
Plant individual plants fairly close together in your salad bowl, around three to four inches apart. Check the plant label and place the tallest-growing plants in the center or background of the bowl in a group. Place the container in a cool location that will receive at least six hours of sun each day. Check daily to see if your salad bowl needs to be watered.
Water until it starts to drain out of the holes. If you have a saucer under your container, pour it out once all the extra water has drained out of the pot.
You can start harvesting in about a month by picking individual leaves from plants. Pick or use scissors to cut off the oldest leaves just an inch or so above the base of the plant. Be careful to not uproot the plant. If you eat a lot of salad, then you may want to plant several containers.
When hot summer weather arrives, it will be time to do one last harvest and cut all the plants off. Buy lettuce seeds in the spring, so you can start a salad bowl again in the fall when cool weather is back.