By cutting the stalks of curly-leaf parsley (Petroselinium crispum) or Italian parsley (Petroselinium neapolitanum) close to the ground, you get a harvest of parsley leaves to add to recipes and also encourage the plant to produce more growth for a later harvest. Hardy from U.S. Department of Agriculture plant hardiness zones 4 through 9, both of these common types of parsley are biennial plants. That means they produce leaves throughout the first year's growth and produce flowers the second year.
When to Harvest
Parsley can be harvested when its leaf stems have three sections, according to The Old Farmer's Almanac. Generally, that's about 70 to 90 days after its seeds were sown. If the leaves start to yellow or the plant develops flowers, then you've waited too long. If the plant develops flowers, not all is lost, however, because you can allow the flowers to develop seeds, which are edible. So when the plant dries out and dies, harvest the seeds.
How to Harvest
Before you harvest a parsley plant, soak your garden snippers or garden knife in a solution that is one part bleach and three parts water for a minimum of five minutes to prevent the spread of plant diseases; rinse the sterilized tool with clean water, and let it air-dry.
A parsley plant's outer leaves are more mature than its inner leaves. So aim to harvest the outer leaves first. Bunch the stalks you want to cut together, and then cut them about 1 to 1 1/4 inches from the crown, a height that encourages more growth throughout the growing season. Because parsley leaves don't stay fresh long, harvest the inner leaves later as needed.
If you want to harvest parsley seeds, wait until the flowers form ball-like seed heads, and then snip off an entire seed head and place it in a pan or over a cloth in a cool, dry location. Some seeds will fall onto the pan or cloth as they dry. When the seed head is completely dry, gently roll it between your hands, allowing its seeds to fall onto the pan or cloth.
How to Use and Store
After harvesting, wash the fresh parsley in clean water. Then place the stalks, which still have their leaves, in a glass of water, and place the glass in a refrigerator. When you want to use the parsley in a recipe, snip off the leaves and discard the stalks. When the parsley starts to wilt or darken, it is past its prime and should be composted or discarded.
An option is to dry harvested parsley by bunching the stalks, leaves included, together with a rubber band and hanging the bunches upside down in a well-ventilated room. When the stalks and leaves are completely dry, crumble the leaves and place them in an air-tight container. Discard the stalks. You can also store the leaves in a zippered plastic bag in a freezer. Use dried or frozen parsley within one year. Place parsley seeds in a jar, and then place them in a dark, cool place.