Growing Coriander in the UK: A Beginner's Guide

Is coriander the same thing as cilantro?

Yes, and sorting this out first saves a lot of confusion. It's all one plant, Coriandrum sativum. In Britain we call the soft green leaf coriander; in the US that same leaf is cilantro, which is why American recipes and growing guides use the other word. The round, dried, peppery-citrus spice is coriander seed.

So a single plant gives you two quite different things, and you grow and time them differently:

• The leaf (the fresh herb for curries, salsa and dhal). You want lots of young, tender foliage, picked before the plant bolts.
• The seed (the warm, sweet spice, and next year's free plants). For this you want the plant to flower, then you let the seed ripen and dry.

Most beginners are after the leaf and get caught out when the plant flowers early. Once you understand that flowering is the plant's whole life goal, the growing strategy makes sense.

Why does my coriander keep bolting?

Bolting is when a plant abandons leaf production and races to flower and set seed. Coriander is one of the quickest herbs to do it, which is exactly why it frustrates so many people. According to the RHS, plants start to flower sooner in hot, dry weather and as summer day length changes, at which point they "stop producing leaves to concentrate on setting seed."

Three things push it over the edge:

1. Heat. A hot, dry spell, or a baking south-facing spot in July, and it's off.
2. Drought. Let the roots dry out and the plant reads it as stress and bolts.
3. Root disturbance. Coriander grows a long taproot and resents being moved. Transplanting or pricking out gives the roots a check, and that shock is a well-known bolting trigger. This is the big reason we sow it direct rather than raising it in trays and planting out.

Coriander isn't a plant you grow once. It's a plant you keep starting.

When and where should you sow coriander in the UK?

Timing is where the UK climate actually helps you, because our summers are rarely brutal for long.

• Under cover from February. You can sow into pots or small trays of peat-free seed compost from February onwards, on a bright windowsill or in a greenhouse. Germination takes about two to three weeks. Sow into modules or a final pot, not a seed tray you'll prick out from, so you don't disturb those roots later.
• Direct outdoors from spring to autumn. Once the soil has warmed in spring, sow straight into the ground or a container where the plants are to crop. The RHS suggests a "sunny or lightly shaded spot," and you can keep going through to autumn.

The clever bit is matching light to season. In spring and autumn, when the sun is gentle, give coriander a sunny position for strong growth. In high summer, move it into light or afternoon shade: a spot that gets morning sun and dappled shade later, or the cooler side of a taller crop. Cooler roots and less midday glare buy you more leaf before it bolts. This is why coriander is a brilliant crop for the shadier corners that tomatoes and peppers would sulk in.

How do you sow coriander?

Sowing is simple enough, and the details that matter are depth, thinness and moisture.

1. 1

   Prepare the spot

   Pick your final growing position: an open patch of moisture-retentive soil, or a pot at least 15cm deep with drainage holes. Rake the soil to a fine tilth or fill your container with fresh peat-free compost and firm it lightly.

2. 2

   Sow thinly, about 1cm deep

   Scatter or space the seeds around 5cm apart in a shallow drill or on the firmed surface, then cover with about 1cm of soil or compost. Sowing thinly matters: crowded seedlings are the ones that damp off and bolt.

3. 3

   Water in and keep moist

   Water gently with a fine rose and keep the surface consistently moist, never waterlogged, while the seeds germinate. Outdoors this takes roughly one to three weeks depending on temperature.

4. 4

   Thin lightly once up

   When seedlings are big enough to handle, thin to about 5cm apart for a leaf crop, or a generous 20cm apart if you're growing plants on for seed. Don't strip it back to bare soil, coriander doesn't like a lot of fuss around its roots.

5. 5

   Sow again in three weeks

   Mark your calendar and sow the next small batch. Successional sowing every two to three weeks is the single best habit for a continuous supply.

How do you harvest the leaves?

Treat coriander leaf as a cut-and-come-again crop. Start picking when plants are around 10-15cm (4-6in) tall and the leaves are bright green and young. That young stage is when the flavour is best and the plant is furthest from flowering.

The golden rule is not to strip a plant bare. Take a few of the outer leaves or snip the top few centimetres from several plants, then let each one recover for a couple of weeks before you go back. Harvesting little and often like this actually helps delay bolting, because you're constantly removing the growth the plant would otherwise push up into a flower stalk. If you ever see the central stem start to lengthen and get feathery, ferny leaves appearing, that's the plant preparing to bolt: pick generously while you still can.

How do you harvest and store the seed?

If you want the spice, or free plants for next year, do the opposite of everything above: let the plant flower. The small white flowers are loved by hoverflies and other beneficial insects, so a bolted coriander plant earns its keep in the garden anyway.

Watch the green seeds form, then let them ripen and turn brown and papery on the plant. When they're fully ripe and brown, cut the whole seedheads (the RHS suggests cutting entire stems), pop them into a paper bag, and hang or lay them somewhere warm and dry for a week or so. The dry seeds will drop into the bag. Store them in an airtight jar for the kitchen, keep a pinch back to sow, and you'll have coriander seed that tastes far brighter than a supermarket jar.

Coriander also self-seeds readily. If you leave a few seedheads to shatter where they stand, you'll often find new seedlings coming up on their own the following spring. It's an easy plant to let naturalise in a quiet corner.

Can you grow coriander on a windowsill or in containers?

Both work well, with a couple of caveats. Coriander actually likes the free-draining conditions of a pot, so containers are a good option, especially if slugs are a problem in your beds. Use a pot at least 15cm deep to give that taproot room, sow a small pinch of seed thinly, and keep the compost just moist, checking daily in warm weather because pots dry out fast.

For a windowsill, spring to autumn is the sweet spot. A bright sill gives you handy kitchen-door coriander through the growing season. In winter, though, low indoor light makes plants go pale and leggy and bolt quickly, so it's not a reliable year-round crop. If you want fresh coriander flavour in the darker months, growing it as microgreens (sowing thickly and snipping the seedlings at a few centimetres tall) is quick, easy and far more forgiving than trying to raise full plants on a dim sill.

What problems should you watch for?

Bolting, first and always. It's covered above, but it really is the main thing that goes wrong. If your plants keep flowering early, work back through the anti-bolt checklist: are you sowing direct, keeping them moist, giving summer shade, and using a slow-bolt variety?

Slugs and snails. Young seedlings are a favourite, especially in damp weather, which is most of the UK for much of the year. Protect direct-sown rows, or start in pots up off the ground where slugs struggle to reach.

Aphids. Greenfly can cluster on soft new growth. A blast of water or a squash between finger and thumb usually sorts small numbers, and the hoverflies drawn to any flowering plants nearby will help keep them down.

Damping off. This is the one that wipes out seedlings overnight, collapsing them at soil level, sometimes under a fuzz of mould. It's caused by soil-borne fungi and is worst in the cool, low-light conditions of an early-spring windowsill. The RHS notes there are no fungicides available to gardeners, so prevention is everything: sow thinly to avoid crowding, don't overwater, keep seedlings well ventilated, and use clean pots and mains water. This is another reason to resist sowing too thickly.

Powdery mildew. In a still, humid spot, stressed or crowded plants can develop a white, dusty coating on the leaves. It's uncommon on coriander in the UK, but good spacing and airflow, the same habits that prevent damping off, keep it away.

Related guides and tools

Coriander is a gateway herb. Once it clicks, the rest of the herb patch is easy. A few sibling guides worth a look:

• Herbs is our full hub of UK herb-growing guides, if you fancy building out the whole patch.
• The best herbs for a British windowbox shows where coriander fits alongside the perennials, and which herbs to skip.
• Keeping indoor basil alive past August is the other tricky tender annual, and the same cool-and-bright logic applies.
• Drying and storing homegrown herbs, including the best way to preserve soft herbs like coriander, which don't air-dry well.
• And to plan your successional sowings so you're never caught short, our planting calendar will tell you what to sow, and when, for your part of the UK.