Cilantro

Identification and origin

Coriandrum sativum belongs to the family Apiaceae, along with parsley, dill and celery. It is native to western Asia, from Türkiye and the Caucasus to Iran, Afghanistan and Pakistan, through the Near East and the Sinai Peninsula. It was already grown in the gardens of ancient Egypt and has been cultivated for thousands of years in India and China. Spanish conquistadors brought it to Mexico and Peru. The epithet sativum means “cultivated.”

It is a fast-growing annual. It first forms a rosette of broad, lobed basal leaves that resemble those of flat-leaf parsley. The foliage reaches 12–18 in tall; when the plant blooms, the flower stalks rise to 2–3 ft and carry finely divided, fern-like leaves. The small white, pale pink or lavender flowers open in loose umbels about 2 in across. They attract beneficial insects such as hover flies and tiny parasitic wasps.

The round fruits turn from green to reddish and then light brown as they dry: these are the coriander seeds. The genus name comes from the Greek koris, a reference to the unpleasant smell of the unripe fruits, which disappears once they are dry. The whole plant is edible. The leaves have a flavor people either love or hate: some find it soapy, a perception partly linked to a gene involved in the sense of smell.

Light

It grows best in full sun but tolerates light shade. In regions with hot summers, afternoon shade prevents sun scald and delays bolting; in summer, sow it in a cooler spot shaded from the midday sun. On a windowsill it often lacks light: it turns pale and leggy.

Watering

Keep the soil evenly moist throughout the growing season. Water needs are greatest during germination and establishment: the surface should not dry out until the seedlings are up. After that, water when the soil starts to dry, without overdoing it: cilantro dislikes soggy soil and very humid, rainy climates, and too much water dilutes its flavor. Mulch applied as soon as seedlings emerge keeps the soil cool and delays bolting. Reduce watering as the seeds near maturity.

Potting mix

It prefers light, loose, well-drained, moderately fertile loam or sandy soil with a pH close to neutral. Before sowing, work well-rotted compost into the top 4–6 in of soil to make a fine seedbed. Go easy on nitrogen: too much fertilizer makes the leaves less flavorful. One or two light feedings during the season are enough.

It grows very well in containers, since it likes good drainage: use a peat-free potting mix and a container deep enough for its long taproot.

Temperature

It is a cool-season plant that grows best between 50 °F and 84 °F. Above 84 °F, or when the soil is warmer than 75 °F, it bolts: it stops producing leaves and flowers. It tolerates light frost and brief cold down to 10 °F, but a hard, prolonged freeze kills it. It is grown as an annual in USDA zones 2a to 11b. Where summers are hot, grow it in spring and fall; where winters are mild, a fall sowing gives a spring harvest.

Repotting

Cilantro transplants poorly because of its long taproot: sow it directly where it will grow, in the garden or in its final container. If you start it indoors, four to six weeks before planting out, disturb the roots as little as possible.

Pots of cilantro sold at the grocery store hold many crowded seedlings meant for a quick harvest: they soon succumb to disease or flower. To make them last, divide the root ball into small clumps as soon as you buy it and repot them right away in fresh potting mix.

Pruning

Pruning and harvesting are the same thing. Start picking when the plants are about 6 in tall, usually a month after sowing. Take the older outer leaves to encourage new growth, or cut a third of the plant at ground level each time. You can also cut the whole clump 1 in above the soil: it regrows for a second cutting.

To extend the leaf harvest, remove flower stalks as soon as they appear: once the plant flowers, the leaves develop an unpleasant taste. Let a few plants bloom, however, if you want to harvest the seeds.

Propagation

Cilantro is grown only from seed. Sow in spring after the last frost, 0–1 in deep, in rows 12–16 in apart. Seeds germinate in one to three weeks depending on temperature. Then thin to 3–6 in apart for a leaf crop, or 8–12 in if you grow it for seed. For a continuous supply, sow again every two to four weeks; summer sowings are not recommended, because plants bolt before producing much.

A seed crop needs at least one hundred days. Wait until the seeds turn light brown, two to three weeks after flowering, then cut the stems and hang them in a paper bag in a dry, airy place: the seeds drop as they dry. Cilantro also self-sows readily. Slow-bolting varieties include ‘Calypso’, ‘Santo’, ‘Slo Bolt’, ‘Leisure’, ‘Marino’ and ‘Cruiser’; ‘Confetti’ has very finely cut leaves. None of them hold up for long in heat and long days.

Common problems

• Rapid bolting: heat, long days, dry soil or late sowing. Sow earlier, mulch, provide afternoon shade and choose a slow-bolting variety.
• Pale, leggy plants: lack of light, especially indoors.
• Water-soaked spots with a yellow edge that turn brown: bacterial leaf spot, the most common disease. Pull infected plants without composting them, water at the base and do not grow cilantro where another member of the Apiaceae grew the previous year.
• Yellowish flowers, spindly, sterile plants: aster yellows, spread by leafhoppers.
• Damping-off, rot, wilt: diseases favored by soggy soil; water without excess.
• Pests: aphids, dislodged with a strong spray of water; cutworms that cut young seedlings off; caterpillars, grasshoppers and leafhoppers.

A single symptom can have several causes: check heat, light, soil moisture and the undersides of the leaves before acting.

Toxicity

No toxicity is reported for dogs, cats or horses. Leaves, stems, flowers, seeds and roots are all edible and widely used in cooking.