How And When To Harvest
Harvest looseleaf lettuce by 2 methods. The best way is to start picking the outer leaves of each plant when they get to be 2 to 3 inches long. Continue picking this way for 4 to 6 weeks until the plant goes to seed (the flower spike grows up out of the center--also called “bolting.”). Then pull the plant and replace it with a new seedling. Another way is to simply cut off the entire bunch of leaves at once about an inch above the ground. The remaining plant stub will produce new foliage in a few weeks. Looseleaf lettuce can be harvested 3 or 4 times before plants need to be replaced. Because this technique works better with some varieties of leaf lettuce than with others, some experimentation may be necessary.
Harvest butterhead lettuce when the head is about the size of your hand. However, it will keep developing and be good for harvest for about 3 more weeks after this stage before going to seed. Cut the loose head off each plant right at ground level. While the plant will still keep growing, it is usually more efficient to plant new butterhead seedlings to assure the next crop.
Harvest Romaine lettuce when the leaves have elongated and overlapped to form a fairly tight head about 3 inches wide at the base and 6 to 8 inches tall. Cut off the entire clump at its base near the soil surface.
Crisphead is also ready for harvest when the leaves have overlapped to form a compact, firm head. It will resemble heads of lettuce you see in the supermarket.
Storing Fresh Lettuce
Best Fresh Storage Method - Looseleaf and butterhead lettuce taste best if eaten shortly after harvest. The excess keeps well in the refrigerator for 1 to 2 weeks if you harvest the leaves, roll them up in moistened, thick paper towels, and put them in an unsealed plastic bag or container. Store at cool temperatures (32° F), and 95% relative humidity. Crisphead types will keep for about 2 weeks in the refrigerator. Use a lettuce spinner or paper towels to eliminate most of the moisture remaining from washing the lettuce before storing in the plastic bag or container. The lettuce will remain crisp for a longer time. Lettuce cannot be canned or frozen.