Dirty air can hurt plants, in fact pollution can do deadly damage. Finally, just like humans, plants need nutrients. The most important being nitrogen, phosphorus and potassium. Nitrogen gives plants their dark green color. Phosphorus helps with flower and seed production and the development of a strong root system.
Potassium helps fight off disease and encourage strong stem growth.
Now you know what it takes. Let's put your skills to work. Try planting your own little lettuce garden in a bag. Take a plastic bag and trim the corners for drainage. Sprinkle a pinch of lettuce seeds on top.