Why does my coriander always bolt?

Coriander bolts fast in heat — anything above 25°C and long summer days triggers it within weeks. UK summer is the worst time for leaf coriander. Sow early (March–April) and late (August–September) instead of June–July. Choose slow-bolting cultivars (Calypso, Confetti) for any summer sowings. Once a plant bolts you can't stop it; pull it and re-sow.

When should I sow coriander seed in the UK?

Late March under cloches in southern England; April outdoors. Successional sowings every 3 weeks until early June, then skip July (too hot), and resume in August for an autumn crop. Hardy varieties can be sown into September for winter cropping under cloches. Coriander wants soil above 10°C to germinate.

Is coriander an annual or biennial?

Annual — grows from seed, flowers, sets seed, dies, all in one season. Most plants bolt and die in 8–12 weeks. The seed they set is the spice (called coriander seed in the UK; Americans call the seed coriander but the leaf cilantro). Save your own seed by letting a few plants bolt and harvesting when the heads turn brown.

What's the difference between coriander and cilantro?

Same plant. Coriander is the UK name and refers to both leaf and seed. Cilantro is the American name for the leaf only (they call the seed coriander). Some recipes specify coriander leaf to disambiguate. UK-grown plants are always called coriander.

Can I grow coriander in containers in the UK?

Yes — and it's often easier than outdoors because you can move pots into shade in hot weather to delay bolting. A 30 cm pot grows enough for a household. Successional sowings every 3 weeks keep the supply going. Indoor windowsill sowings work year-round but the leaves are weaker-flavoured than outdoor.

When is coriander ready to harvest?

Leaf: from about 4 weeks after sowing, when stems are 15 cm long. Pick whole stems from the base. Seed: 12–16 weeks after sowing, when the seed heads have turned brown and the seeds rattle when shaken. Cut whole plants, hang under cover to dry for a fortnight, then thresh.

Coriander / cilantro

Coriandrum sativum

herb☀️ full-sun🪴 well drained loam📏 small🌡️ RHS H3–H4

📋Quick Facts

Height

0.5-0.6m

Spread

0.3-0.4m

Water

💧💧 Average watering

Hardiness

Zone 2-11

About

Sow coriander seed direct from late March to August in successional batches every three weeks. It bolts fast in heat — UK summer is exactly the wrong time for leaf coriander, so sow in spring and again in autumn for cool-season cropping. The leaf (cilantro to Americans) is what most home gardeners want; the seed is the spice and gathers naturally once the plant bolts. Coriander is hardy (RHS H4) and tolerates light frost as young plants. Choose slow-bolting cultivars (Calypso, Confetti) for any summer sowings. Sow thinly into well-drained soil; pick leaves from the bottom of the plant before flower stems appear. One plant gives leaf for about three weeks, so plant successionally.

Top tip

Hates heat and drought; sow in cool periods and pick leaves before plants run to seed.

Also known as: Coriander / cilantro, Coriandrum sativum, Kolendra siewna, Coentros (planta inteira), Koriander, Coriandre (plante entière), cilantro

How to grow coriander / cilantro

1
Sow direct
Late March to August in successional batches every 3 weeks. 1 cm drill, sow thinly, cover lightly. Coriander hates root disturbance; sow where it's to grow rather than transplanting.
2
Choose slow-bolting cultivars for summer
Calypso, Confetti, Cilantro (the variety, not the herb). These run to seed weeks later than standard coriander in hot weather.
3
Thin to 5 cm
When seedlings have 2 true leaves, thin to 5 cm apart. Use the thinnings — even small coriander leaves are useful in the kitchen.
4
Provide afternoon shade in summer
From late June, coriander bolts in heat. Plant under taller crops or use shade netting. Cool-season sowings in autumn produce the longest pick of the year.
5
Pick from the bottom
Pick whole stems from the base of the plant. The plant continues producing from the centre until it bolts.
6
Let some plants run to seed
For coriander seed, let one or two plants bolt and flower. Wait until the seed heads turn brown, then cut whole plants and dry under cover for a fortnight. Shake seeds out into a tray.
7
Sow again for autumn cropping
Mid-August to mid-September sowings produce leaf coriander through to first frost in November.

Common questions

Pest Resilience

3/5 — Average

Aphids can be an issue; bolts quickly so pests rarely have time to build up.

Companion Planting

Grows well with

Spinach Lettuce Tomato Pea

Keep apart from

Fennel bulb

Visual Characteristics

Fruits

Yes

Harvest: Spring to autumn / fall

🍳

Culinary

Culinary Use

Curries, salsa, Thai soups, guacamole, stir-fries, chutneys, pho

The coriander / cilantro year in your garden

Dispatching imaginary bots to check your garden out...

What to do now

How to Propagate

🌰Seed

Easy

This plant produces viable seeds for propagation

Hardiness Zones

H1a (tender)H7 (very hardy)

H1a

H1b

H1c

RHS H3–H4

USDA 8 equivalent