Loosen the soil at the selected garden site to a depth of 12 inches. Bust up any large soil clumps because they may interfere with seed germination.
Mix 4 inches of organic compost with the turned soil. Incorporate 5-10-10 fertilizer, at a rate of 3 lbs. for every 100 square feet of planting space.
Use a garden hoe to create rows that are 12 to 15 inches wide. Allow a space of approximately 18 inches between each row.
Sow the Parris Island romaine lettuce seeds 1/4 inch deep. Water until the soil feels lightly moist. Continue to water lightly whenever the top 1/2 inch of soil feels dry.
Thin the seedlings when they are 3 inches tall. Allow a space of 6 inches between each.
Spread a 2- to 3-inch layer of organic mulch around the plants after thinning. Keep the mulch at least 3 inches away from the plants.
Harvest Parris Island lettuce by cutting the leaves off with scissors when they reach the desired size. Cut every other plant in the row back to soil level when harvesting so that the remaining plants have more room to grow.