TransplantingSilvestri recommends starting your parsley seeds eight to ten weeks before your last frost indoors. In Zones 7 and below, you can protect your parsley plants through the winter by covering them with a frost blanket or heavy mulching. They are actually the caterpillars of the black swallowtail butterfly, which feed on parsley leaves until they pupate and emerge as stunning butterflies. Parsley plants are biennial, which means they live for two growing seasons. In its first season, parsley produces vibrant, edible leaves, whereas in its second season, it produces flowers and seeds.