All seed-bearing plants produce leaves to collect sunlight and flowers to pollinate and fertile seeds. When lettuce is ready to flower, the plant produces a central reproductive shoot that produces a cluster of tiny flowers known as pappuses.
These little pappuses are attached to several seeds, which form inside the flower head. Eventually, the heads will turn yellow or brown and white puffs will form on top of the flowers.
The pappuses will fall away from the flowers as the heads mature, but the seeds are still attached to them and can be collected by hand. To harvest the seeds, gently roll the flower head between your fingers to break open the heads and gather the seeds.
One plant can easily produce hundreds of seeds if you harvest them regularly and dry the seeds in a paper bag or basket before storing them. Once dried, store them in an airtight container or plastic bag until you are ready to plant them.
Lettuce can be planted year-round in many garden zones and can also be grown as a biennial in milder areas. These greens will go dormant during the winter and re-leaf in the spring of the following year.
A well-tilled, organic seedbed is crucial for germination. It's important to keep weeds to a minimum and avoid overwatering the seeds. If a lot of sand or stones are present in the soil, this may inhibit germination and result in poor quality seeds.