Chervil Care: Shade, Steady Water and Delaying the Bolt

Shade is the whole trick

Almost every herb guide tells you to give herbs full sun. Chervil is the exception, and treating it like basil or thyme is why so many plants bolt within a month of germinating. It evolved in woodland edges and hedge bottoms, and it wants dappled light, cool soil and shelter. In a hot open bed it flowers before it has made a plant worth cutting.

The practical target is two to four hours of gentle morning sun and shade from late morning onwards. Under deciduous trees, on the north side of a wall or fence, in the shadow of taller crops, or in the space beneath a fruit bush all work. Deep shade all day is too much and produces stretched, pale, thin flavored leaf, but you will get away with far more shade than you expect.

The rule is about heat rather than light as such. In the cool weeks at either end of the year chervil takes full sun happily. It is the combination of sun and warmth that starts the flower stem.

Never let the roots dry out

A single afternoon of hard wilting is enough to commit a chervil plant to flowering, and once the stem is running nothing brings it back to leaf. Steady moisture is not a refinement here, it is the difference between a plant you cut for two months and one you compost after three weeks.

Water deeply rather than often. Let the top half inch (1 cm) of soil dry and then water until the ground is wet four inches (10 cm) down, or until it runs freely from the bottom of a pot. Light daily sprinkling keeps the taproot shallow and makes the plant more vulnerable to the next hot day, not less.

1. Mulch as soon as the seedlings are thinned An inch (2 to 3 cm) of leaf mold, fine bark or straw around the plants keeps the soil cool and roughly halves how often you need to water. Keep the mulch off the crowns, which rot if they sit damp.
2. Water in the morning A plant that meets the warmest part of the day with wet roots does not wilt. Watering in the evening leaves the fine foliage damp all night, which is how mildew and leaf spot start on a crowded row.
3. Check containers twice a day in warm weather A pot under eight inches (20 cm) across can go from moist to bone dry in half a day. If you cannot check it that often, move it into deeper shade rather than risk the wilt that triggers bolting.

Wilting at midday that recovers by evening does no lasting harm. Wilting still visible at dusk means the roots were genuinely dry, and that is the wilt that ends the plant's useful life.

Feed almost not at all

Chervil is a short lived plant on decent soil and needs very little. Ground with plenty of organic matter in it carries a crop from sowing to the last cut with no feeding whatsoever. Pushing it with nitrogen gives soft floppy growth that aphids find first, and soft leaf carries noticeably less of the anise scent that is the reason to grow the plant.

Containers are the exception, because watering leaches the compost. A dilute balanced liquid feed every two or three weeks while you are cutting is enough. Stop feeding a plant you are keeping for seed once the flower heads open, or you get a lot of leaf and few ripe seeds.

Containers, and keeping the rootball cool

Because the plant roots straight down, depth matters more than width. Eight inches (20 cm) of compost is the working minimum and ten to twelve inches (25 to 30 cm) is better. In a shallow tray the taproot hits the bottom, turns sideways and the plant reads the check as a season ending, so it flowers early regardless of how carefully you water it.

Use an ordinary moisture retentive compost rather than a gritty free draining mix. Chervil wants water held around the roots. A dark plastic pot standing in sun can push the rootball above 95F (35C) on a warm afternoon, which alone will start the flower stem, so use pale pots or stand one pot inside another.

1. Sow into the final pot Fill it, water it, sow into the damp surface and thin in place. Chervil should never be potted up, and a plant moved from a small pot to a large one is a plant that will flower within a fortnight.
2. Three or four plants to an eight inch pot A dense clump of a dozen seedlings shares one small volume of water, runs dry every afternoon and bolts as a group. Thin ruthlessly even in a container.
3. Move the pot as the season turns Chervil in a pot can follow the shade. Keep it in dappled shade while it is warm and move it into full sun once the weather cools, which extends the cutting season at both ends.

Chervil grows well on a cool windowsill out of direct sun, but not on a hot sunny one. A bright north facing sill in cool weather gives a better plant than a south facing sill in summer.

Reading the plant

Chervil signals what it is doing through the shape of its new growth. Good leaf is broad, soft, finely divided and lies low in a loose rosette. When the plant decides to flower, the leaves coming from the center turn narrow and thread like and the center lifts on a stem. Learning to see that change a week early is what lets you take a last useful cut instead of finding a flowering plant.

Pinching out the first flower stem buys a week at most. The leaf that follows is sparse and coarse, and the plant is already spending itself on seed. Treat the first flower stem as the signal to sow the next row.