When I visit other gardens I am often intrigued by things I see other gardeners do. Janet Livesay, in Lake Oswego, Oregon, had a planter that fit over the railing of her deck. She used Black Gold Natural & Organic Potting Soil and planted lettuce from seed.
Since the deck is by a door to her kitchen, she could easily cut the lettuce whenever she was making a salad. She was innovative with wanting to harvest lettuce over a long period and so she also planted seeds in small nursery pots at various intervals throughout the summer. When the lettuce in the planter was past its prime, she simply replaced it with new plants. And with the planter being off the ground, she did not have to worry about slugs eating the lettuce.