Trim the parsley down to the healthiest plants at the end of the traditional growing season. Watch for the plants to emerge in the early stages of the next growing season.
Wait for flowers to sprout on the parsley early in the growing season. Cut the flowers at the base of the stem when the seeds in the flower turn brown. Place each flower upside-down in a fresh paper bag.
Shake the ripe seeds from the flower head. Remove the flowers from the bag and set them out to dry for 1 to 2 days. Place the flower in the bag and repeat the process to remove the remaining seeds.
Lay the seeds out in an area with good air circulation and turn them daily for 2 weeks or until dry. Spread them on a paper bag or in a shallow tray to keep them contained.