Cilantro / Coriander

As soon as the soil is workable, sow seed a half inch deep, thinning later to about 2 inches apart, in rows at least 15 inches apart. Direct sowing is the simpler path. You can start indoors 4 to 6 weeks before transplanting, but minimize root disturbance when the seedlings go out. Cilantro drives a long taproot early and resents having it disturbed, so a plant moved roughly tends to check. Direct sowing sidesteps the problem entirely; the extension guidance if you do transplant is to disturb the roots as little as possible.

Apply about a quarter cup of a nitrogen fertilizer such as 21-0-0 per 25 square feet, one to two times across the growing season. The leaf is the crop, and nitrogen is what builds leaf. But cilantro is a short, fast plant that finishes in weeks - it cannot use a heavy program, and feeding past this only pushes soft growth.

Once seedlings are up and handleable, thin to about 2 inches apart if you are growing for leaves, or 8 to 10 inches apart if you want the plants to stand and ripen coriander seed. Leaf cilantro is cut young and never needs room. A plant that has to stand and carry a seed head to maturity is a much bigger plant, and the extension spacing for a seed crop is four to five times wider than for leaf.

Sow a fresh short row every 2 to 3 weeks rather than one big planting, and continue successive plantings until late summer if you want a continued harvest. Expect the rows you sow into peak heat to bolt early and give you little leaf. A cilantro plant has one leaf phase and then it flowers; there is no cutting it back into a second youth, so a continuous supply comes from repeated sowings rather than technique. Heat is what triggers bolting, so sowings that mature in hot weather run to flower fastest.

Check the planting for leafhoppers through the warm months - small wedge-shaped insects holding their wings tent-like over the back. Pull and remove any plant showing yellowed, stunted or distorted growth, since an infected plant will only grow tall and spindly and go sterile. Leafhoppers vector aster yellows, which is a phytoplasma rather than a fungus - nothing you spray on the leaf cures an infected plant, so the only useful step is removing the infected plants before hoppers move the disease down the row.

Mulch the row and give the planting shade from mid-afternoon sun, either from a taller neighbouring crop or from shade cloth. Water consistently while you do it. Heat is the trigger that flips cilantro from leaf to flower, and both mulch and afternoon shade work on the same lever - they hold the soil cool, which delays the switch and keeps the leaves from turning bitter.

When plants stand about 6 inches tall, cut roughly a third of the plant at ground level, or pick sparingly once plants reach 4 to 6 inches. Pinch out flower stems as they appear. Wrap cut leaves loosely and refrigerate; they hold about a week. Cutting at ground level takes whole stems and leaves the growing point to push again, while pinching the flower stalks extends the leaf harvest. Once bolting is truly underway the leaves go bitter and no amount of cutting brings them back.

Once you let a planting flower, leave it standing and wait for the seed heads to turn brown, then gather the seed as it ripens. If heads start shattering, cut them off into a paper bag and hang it until the plant dries and the seed falls to the bottom. Coriander seed finishes drying down on the plant, and the brown head is the signal that it is mature enough to store and use; gathering green costs you keeping quality. Left alone, the plant will also self-seed the bed for next season.