Lettuce is a cool-season crop. Grow it in the garden in spring before the temperatures become too warm or in fall after temperatures have cooled down. Red leaf lettuce varieties are slow to bolt when the weather begins to warm, effectively extending your harvesting season. Certain varieties of red leaf--like Ruby--are less likely to get brown tips, called tipburn. The purplish-red color of red leaf lettuce is a colorful addition to salads and as a garnish with other dishes.
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.