How to Sow Chervil: Fresh Seed, Shallow Cover and No Transplanting

Sow where the plants are going to stand

Chervil puts down a thin taproot within about ten days of germinating, and that root does not tolerate being broken. Lift a seedling, pot one on, or transplant a tray of them, and the survivors sit still for a fortnight and then run to flower without ever making a decent plant. There is no technique that gets around this. Sow it in its final position and you avoid the problem entirely.

That applies to containers as much as to open ground. Fill the pot you intend to keep the plant in, water it, and sow into the damp surface. If you have bought a pot of chervil already growing, plant the whole rootball out without teasing it apart at all, and expect a shorter life from it than from anything you sowed yourself.

1. If you must start under cover, use deep cells Sow three or four seeds into cells at least three inches (8 cm) deep and plant the whole undisturbed cell out within three weeks of germination. Never separate the seedlings and never wash soil off the roots.
2. Choose a shaded spot before you open the packet Chervil is one of the few herbs that genuinely wants shade. A bed that gets morning sun and nothing after midday, or the north side of a taller crop, will give you weeks more leaf than an open sunny bed.
3. Rake the surface fine The seed is small and sown shallow, so a cloddy surface leaves half of it stranded on top to dry out. Break the top inch (2 to 3 cm) down to a crumb before you sow.

Chervil, parsley, dill, coriander and carrots all share this dislike of root disturbance. If you already direct sow your carrots, treat chervil exactly the same way.

Use seed from the current year, not last year's packet

Chervil seed is short lived. Kept in a warm kitchen drawer it can lose most of its viability in a single year, and a two year old packet often gives nothing at all. Far more chervil failures come down to dead seed than to sowing depth or temperature, and because the seedlings are slow to appear anyway, people usually blame the weather instead.

Buy fresh each season, or save your own from a plant you let flower and store it cool and dry. If you are unsure about a packet, spread twenty seeds on damp kitchen paper in a sealed bag at room temperature and look at them after two weeks. If fewer than half have chitted, sow at three times your normal rate or start again with new seed.

Depth, spacing and soil temperature

Chervil germinates in the cool. It moves at soil temperatures from the mid forties Fahrenheit upward and is happiest between 55F and 65F (13C to 18C). Above about 75F (24C) germination becomes erratic and the seedlings that do come up bolt almost immediately, which is why a midsummer sowing so often looks like a seed failure when it is really a heat failure.

Sow shallow. An eighth of an inch (3 mm) of fine soil is enough, and light helps rather than hinders, so resist the urge to bury it properly. Keep the surface damp until the seedlings appear, which takes two to three weeks in cool soil and can stretch longer in a dry spell.

Water the drill before you sow rather than after. Watering a shallow sowing from above floats the seed into drifts and leaves gaps in the row.

The two sowing windows, and the one to avoid

Chervil has two good sowing seasons and one bad one. Sow from late summer into early autumn for the main crop: those plants grow through cooling weather, sit through winter as small tough rosettes and give you thick, sweet leaf from the first mild spell until they flower in mid spring. This is the sowing that produces the best chervil of the year, and it is the one most gardeners never make.

The second window is early spring, as soon as the soil is workable. These plants crop quickly but have a short run, because rising temperatures and lengthening days push them into flower within six to ten weeks of germinating. The window to avoid is late spring into summer. Seed sown then germinates badly, and whatever comes up flowers before it has made a plant worth cutting.

1. Sow a short row every three weeks A yard (1 m) of row at a time is plenty for most kitchens. Successional sowing matters more with chervil than with almost any other herb, because an individual plant gives you a narrow window of good leaf and then finishes.
2. Give the autumn sowing some cover A cloche, low tunnel or cold frame over the autumn row keeps the leaves clean and lets you cut through the coldest weeks. The plants are hardy without it, but winter rain flattens the foliage and mud spoils it.
3. Sow in the shade of a summer crop If you want chervil in summer at all, sow it on the shaded north side of beans, sweetcorn or a fruit cage where it gets an hour or two of light and no direct midday sun.

Thinning, and what to write down

Thin in two passes rather than one. Take the row down to about three inches (8 cm) apart once the seedlings have their first true leaves, then to a final six to nine inches (15 to 23 cm) a fortnight later when you can see which plants are strongest. Snip the unwanted ones off at soil level with scissors instead of pulling, so the roots of the keepers are left alone. The thinnings are worth eating.

The habit that pays off is recording the sowing itself. Chervil is slow to emerge, short lived and heavily weather dependent, so a season's worth of notes tells you more than any general advice can.

1. Record the sowing date and where the row is Note the date, the position of the row and how much shade it gets. Next year you will be comparing a shaded row against a sunny one and the difference in how long they lasted is the whole lesson.
2. Record the date the seedlings emerged The gap between sowing and emergence tells you whether your soil was warm enough. Three weeks is normal in cool soil. Nothing after four weeks usually means old seed, and that is worth knowing before you sow the same packet again.
3. Record the date the first plant ran to flower That single date, set against the sowing date, gives you the length of the useful window for your garden and your season. After two years of it you will know exactly when to make each sowing.