Parsley is a biennial herb grown as an annual for its flat or curled leaves, used fresh or dried. Flat-leaf (Italian) parsley has the stronger flavour for cooking; curled parsley holds up better as a garnish and in the border. It is hardy, productive, tolerates light frost, and often overwinters in a sheltered spot to flower in its second year.
Seed is slow to germinate, often three to four weeks. Soak it overnight, sow a quarter inch deep, and keep the bed consistently moist until it is up; or start it indoors eight weeks before last frost. Set plants 6 to 8 inches apart in rich, moist soil in sun or part shade. Harvest the outer stems first and the centre keeps producing all season. Second-year plants bolt and turn bitter, so most gardeners replant each spring.
Parsley is a host plant for the black swallowtail butterfly, whose striped green caterpillars appear in midsummer; plant enough to share and move them to a spare plant rather than killing them. The umbels of a second-year plant feed hoverflies and tiny wasps. Deer generally leave it alone.
Damping Off
Seedlings collapse at the soil line with thin, water-soaked stems; seeds may fail to emerge or rot before sprouting.
Sow in well-draining mix, avoid overwatering, and ensure good airflow. Remove affected seedlings and let the surface dry between waterings.
Crown Rot
Lower leaves yellow and wilt; the base of the rosette turns brown and soft, sometimes with white fungal threads at the soil line. Plants collapse in wet conditions.
Remove and destroy affected plants. Improve drainage and avoid overhead watering. Do not mulch directly against the crown. Space plants for airflow and avoid replanting in the same wet spot.
Septoria Leaf Spot
Small tan to brown spots with dark borders on leaves, often with tiny black specks at the center. Spots merge and lower leaves yellow and die.
Remove infected leaves and avoid overhead watering. Space plants for airflow and rotate planting location each year. Apply a copper-based fungicide if spread continues.
Aphids
Aphididae →Clusters of small soft insects on new growth and flower buds.
Knock off with a strong jet of water. Ladybirds and lacewings are natural predators. Insecticidal soap as last resort.
Carrot Rust Fly
Psila rosae →Rust-colored tunnels and brown scarring through the outer root. Foliage may yellow or wilt. Larvae are small white maggots in the root surface.
Cover beds with insect netting at sowing. Delay sowing past the first generation and avoid leaving thinnings in the bed, since their scent attracts flies. Rotate crops yearly.