My fiancé and I are members of the Sepulveda Community Garden Center in Encino where we have two plots. Our first plot (in the photo below) is 30 x 20ft, and our newer plot is just under 10 x 20ft of space.
In this larger plot we had two lettuce plants that bolted, which means they started blooming flowers and going toward forming seeds.
On our last garden visit, we pulled the plant and cut the tops with the seeding flowers off. We then recorded the seed harvesting progress in the video below. Enjoy!