Chervil is the most delicate of the fines herbes: lacy, fern-like leaves with a subtle anise flavour that disappears with heat, so it goes in at the very end of cooking or is used raw, in omelettes, with fish and in spring soups. It grows 12 to 18 inches and is one of the few herbs that prefers shade.
It thrives in cool weather and runs to seed once temperatures climb above 70°F. Direct sow a quarter inch deep a few weeks before last frost and again in late summer for a fall crop, in rich, moist soil in dappled light; it develops a taproot and resents transplanting, so sow where it will grow and thin to 6 to 9 inches. Keep it watered, and pick the outer leaves from the time the plant is 4 inches tall.
It self-seeds freely once established, and the volunteers that come up in late summer under taller plants are often the best crop of the year, lasting into winter under a cloche. The small white umbels feed hoverflies and parasitic wasps if a few plants are allowed to flower. Deer leave it alone. It is native to the Caucasus and southern Russia.
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.
Downy mildew
Yellowing on top of leaves with grey-purple fuzz underneath. Spreads rapidly in humid conditions.
Remove affected leaves. Improve air circulation. Avoid overhead watering. Copper spray as preventive.
Powdery mildew
White or grey powdery coating on leaves - usually starting on older growth in humid conditions or when nights cool.
Improve air circulation by thinning plants. Apply neem oil or potassium bicarbonate spray at first sign. Avoid overhead watering.
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.