CorianderCoriandrum sativum

In spring and autumn, coriander wants sun; in summer, it prefers partial shade, where the long days and heat push it less quickly into flower. Best is to move it with each sowing: a row facing due south in April, a row in the light shade of climbing beans or an east-facing wall in June-July, then back in the sun in September. The soil should be light and moist, without excess richness. Keep it away from fennel, which hinders it, and from dill, with which it can cross if you are saving seed.

Loosen to 20 cm, as coriander has a taproot, and work in a kilo or two of mature compost per square metre, no more: soil that is too rich gives bland leaves and a plant that bolts. Rake the surface very fine, as germination is erratic in lumpy soil. In our capping loams, cover the drill with sieved compost. On heavy clay, a spadeful of sand along the seed row helps the root. A sowing on a bed that carried peas or lettuces in spring finds perfect soil.

Sow in place from April to September, in small amounts repeated every three weeks: a one-metre row or a pot each time. First rub the round seeds between your hands or roll them under a small board to split them in two, which speeds up germination. Sow 1 cm deep, one seed every 3 cm, in rows 25 cm apart, cover with fine compost and keep moist. Germination in ten to fifteen days at 15 °C. The late August and September sowings, in less of a hurry to flower, are the most productive in leaves and hold on under fleece until November.

Two types exist, and the packet does not always say so. Leaf varieties, described as slow to bolt, such as Calypso, Leisure, Santo or Cruiser, keep their broad leaves three to four weeks longer and are the right choice for the kitchen. Seed varieties, described as Moroccan or large-seeded, flower quickly and are sown for the umbels and the September harvest. A pot of coriander from a garden centre or supermarket, sown densely and forced, bolts as soon as you take it out; better to eat it within the week and sow your own.

Coriander cannot stand transplanting: any injury to the taproot or any extended stay in a pot triggers flowering within a fortnight, with no leaves to harvest. So always sow it where it will grow. If you want a head start, sow in March in biodegradable pots, three seeds per pot, and plant the whole pot as soon as the seedlings have two true leaves, without waiting. A bought pot is removed without touching the root ball and planted at once, in partial shade, with a copious watering. Then thin the sowing to 15 cm as soon as the plants have four leaves.

Coriander does well in a pot, provided it has depth: 20 cm at least for the root, in a window box 40 to 50 cm long placed facing east or west, never due south in summer. Ordinary potting compost lightened with a quarter of sand, clay pebbles at the bottom. Sow directly in the window box about twenty split seeds spread over the surface, thin to 10 cm, water as soon as the surface dries, every two days in summer. Plan for two window boxes that you resow alternately every three weeks, so as always to have young leaves to hand.

The first mistake is sowing just once, in May, a long row: everything flowers in June and the gardener concludes that coriander "bolts". It does bolt, yes, but you sow it little and often. The second is transplanting seedlings or keeping a shop-bought pot on a warm window. The third is letting the row dry out in June, which hastens flowering. Finally, waiting for the large leaves of "real" coriander when the plant is already making fine, feathery leaves: these announce the flower, it is time to resow and leave that plant for seed.

Coriander wants permanently moist soil, without ever being drowned. Water with a fine spray, preferably in the morning, four to five litres per square metre every two or three days in dry weather, more on a sowing still coming up, which must never dry out. A single day of dry soil in June is enough to persuade the plant to flower. In a pot, water as soon as the surface pales, every two days in summer, emptying the saucer. A coriander that droops in the morning lacks water; a coriander that yellows in sodden soil has too much.

After thinning, mulch the row very lightly, 2 cm of well-dried grass clippings or flax shives, to keep the soil cool without smothering the young plants. Feeding: almost nothing. The compost from the soil preparation is enough; excess nitrogen gives large but bland, fragile leaves. A single watering of nettle liquid diluted to 5 % after the first cut relaunches regrowth. In a pot, a half-dose of liquid organic feed every three weeks is sufficient. A pale coriander in a pot lacks light or water rather than food.

Harvest as soon as the plants are 15 cm tall, cutting the outer stems with scissors 3 cm above the ground, without touching the heart: the plant then gives two or three cuts ten days apart. Pinch out the first flower stem as soon as it shows, which gains a fortnight of leaves, then let it be. The real secret lies elsewhere: resow every three weeks from April to September, a metre at a time, and pull up bolted rows without regret, except for two or three plants left in flower for the insects and the seeds. Coriander is managed like the radish, in succession, not like a perennial.

Coriander is little attacked. Aphids sometimes lodge on the umbels in June; a jet of water, soft soap at 5 % or simply the hoverflies, drawn by its own flowers, deal with them. Slugs nibble young sowings as they come up: evening collection and ash around the row. Rot at the crown or a bacterial blight spotting the leaves appear in heavy, overwatered soil; space out, water at the base in the morning, and change the spot. Repeated sowing on the same bed encourages soil-borne diseases: alternate with families other than the umbellifers.

Early April, first sowing in full sun, under fleece if the nights freeze. May, thinning, first cuts, second sowing. June, sowing in partial shade, diligent watering, pinching flower stems, a few plants left in flower. July, spring rows pulled up or left for seed, new sowings in light shade. August, harvest of the browned seeds, autumn sowing, the most productive. September, last sowing under cover or in a pot. October-November, picking leaves under fleece or a cold frame until the hard frosts. A late September sowing in a cold greenhouse sometimes gives leaves in February.

Cut the leaves in the morning, when they are broad and toothed, in the three to four weeks after germination, before the fine leaves appear. For the seeds, let two or three plants flower in June-July, wait until the umbels turn brown and the seeds rattle when rubbed, cut the stems on a dry morning in late August or September, and hang them upside down in a paper bag for a fortnight. Thresh, winnow, dry for another week. Some will go in the grinder, the rest will serve next year's sowings, coriander being one of the few herbs where you are entirely self-sufficient.