Parsley (Petroselinum crispum) is an herbaceous plant whose distinctively flavored leaves and stems are commonly used as a culinary herb. The most widely grown garden species is curly-leaf parsley (Petroselinum crispum var. crispum), but other varieties, such as Italian flat-leaf parsley (Petroselinum crispum var. neapolitanum), are also common.
Parsley is a biennial, which means that it flowers, sets seed and dies after its second growing season. It is winter hardy in U.S. Department of Agriculture plant hardiness zones 5 to 8, but in colder climates it may be grown as an annual. Although the optimal temperature range for parsley is between 50 and 70 degrees Fahrenheit, it can tolerate temperatures as low as 20 degrees F. Plants may struggle or die when temperatures climb above 90 degrees F.
Planting and Timing
Parsley seeds are slow to germinate, and they may take between two and five weeks to sprout after they're planted. Sow the seeds in the garden after the soil temperature has reached 50 degrees F, and to encourage faster germination, soak the seeds in warm water for a day just before planting. Seeds may also be started indoors about six to eight weeks before the last frost of the spring to get a head start on the growing season, and then planted in the garden after the possibility of frost has passed.
Parsley does best in locations that receive full sun for at least six to eight hours a day. It grows best in soil that is well-drained but that contains plenty of moisture-retaining organic material.
Fertilization and Watering
Parsley prefers soil that is consistently moist but not soggy. Monitor soil moisture so that the soil never dries out completely, and water thoroughly about once a week, so that the soil is saturated to the level of the plant's roots.
Fertilizing parsley twice during the growing season with 3 ounces of 5-10-5 fertilizer per 10 foot row will encourage vigorous growth. Water well after fertilizing.
Thinning and Harvesting
Once parsley seedlings are 2 or 3 inches high, thin them so that plants are spaced 10 to 12 inches apart within the bed.
When the plants are established and growing well, usually between 70 and 90 days after the seeds are sown, leaves and stems can be harvested from the outer part of the plant. Harvest by clipping off stems close to the level of the soil to maximize new growth; cutting off just the leaves slows down the production of new stems.