Lettuce is a cool season vegetable that thrives in spring and fall gardens. Once temperatures begin to raise in summer, lettuce bolts, sending up a seed stalk and stopping edible leaf production. Instead of digging up the plants at this point, leave one or two lettuce plants in the garden and allow them to flower and produce seed. Harvest and save the seed to plant our fall lettuce crop or the next spring's crop. This allows you to save money on purchasing seeds.
Cut off the flower stalk once the flowers fade and the seed tufts are in place. These resemble the fluffy heads of dandelion flowers gone to seed. Cut the stalk off beneath the lowest tuft with a knife or shears.
Hold the seed stalk over a shallow bowl. Rub each tuft between your fingers, loosening the seeds so they drop into the bowl.
Place the bowl in a warm, well-ventilated room for three to five days. This allows the seeds to finish drying completely.
Label an envelope with the harvest year and lettuce variety. Place the lettuce seeds in the envelope.
Place the envelope in a jar and screw the jar's lid on tightly. Store the seeds in the refrigerator or in a cool, dark place until you are ready to plant them.