Gardeners can choose from a wide variety of leaf lettuces. Green varieties include Black-seeded Simpson, Salad Bowl and Oak Leaf, while red selections include Red Sails, Red Fire and Ruby. Choose leaf lettuce seed that has been treated with a fungicide to limit damping-off, which causes seedlings to soften and fall over at the soil line. Leaf lettuce does best in cool weather, and goes to seed quickly during hot periods. Lettuce needs lots of water for germination and seedling development, and benefits from being grown in the shade of other taller plants.
Remove any weeds and rocks from the planting area. Dig plenty of compost into the soil as early in the spring as it can be worked, and rake it smooth.
Plant the leaf lettuce seeds 1/4- to 3/8-inch deep and eight to 10 inches apart. Sow seeds more closely together if you plan on harvesting some of the leaves as baby lettuce.
Rake soil gently over the seeds. Water lightly so as not to disturb them. Water regularly and more heavily during hot weather.
Cultivate regularly between the rows of new seedlings to keep weeds down. Pull any weeds that will compete with the lettuce for water and nutrients. Pick young lettuce leaves when they reach 3 inches, as this encourages the production of more leaves.
Harvest the mature lettuce in 50 to 60 days, or just pick some of the larger leaves to make room for new growth. Remove any plants that have bolted -- gone to seed -- which will appear as long stalks with blossoms along the sides. Lettuce that has gone to seed usually tastes bitter.
Allow the red leaf lettuce to grow to the desired size. Let leaves reach at least 4 inches in length before harvesting.
Remove outer leaves by cutting them off 1 inch from the base of the plant with sharp leaves. Harvest with this method as lettuce is needed; the inner leaves will continue growing.
Harvest greater quantities by cutting off the entire top two-thirds of the lettuce leaves. Leave the base intact so side shoots will form.
Harvest side shoots when they are mature enough by removing single leaves from the outer part of the plant or cutting the entire plant as you did originally. Red leaf will continue producing new side shoots until it bolts in summer.