Grow parsley in rich, well-drained soil in full sun or part shade in early spring or during the fall if the summers are very hot. Plants grow small flowers that should be cut back to avoid bitter leaves when harvesting, unless you wish to harvest and replant the seeds next season. As a biennial, parsley will grow to its full size the first season and flowing winter, will flower, set seed, and die the second. In mild climates you can keep harvesting parsley leaves all through winter, while in hard-freezing winter regions, transplant parsley into a container and over winter bring indoors to grow on a sunny windowsill.