Why Does My Coriander Bolt? Causes and Fixes

Coriander bolts when it is stressed. The most common triggers in a UK garden are heat, dry roots and the shock of being transplanted — and the fix is mostly about how you sow and water it, not what you do to a plant that has already run to seed. Get the sowing and watering right and you can keep cutting leafy coriander for weeks instead of watching it shoot up and flower within a fortnight.

It helps to know one thing up front: coriander is genetically primed to flower fast. It is an annual that wants to set seed and finish in a single season, so it does not take much to tip it over the edge. Your job is to keep it relaxed and growing leaf.

What bolting looks like

Bolting is when a plant abandons leafy growth and races to produce flowers and seed. With coriander it is unmistakable. The plant suddenly grows taller and more upright, the soft rounded lower leaves give way to thin, feathery, ferny ones higher up, and a flower stem pushes through the centre. Within a week or two you get clusters of small white or pale-pink flowers.

Once that switch flips, leaf production all but stops. The few leaves you do get are sparse and taste sharper and more bitter than the lush flat lower leaves you actually want for cooking. There is no reversing it — you cannot prune a bolting coriander plant back into leafy growth. The lesson is in the next sowing, which is why coriander rewards a little-and-often approach more than almost any other herb.

Most likely causes (and the fix for each)

Here are the triggers, roughly in the order they catch UK growers out.

1. Heat and long summer days

This is the big one. Coriander is a cool-season herb. It is happiest in the mild conditions of spring and early autumn, and the long, warm days of June and July are precisely what tell it to flower. A spell of hot weather, or sowing into the middle of summer, will bolt it almost on cue.

The fix: lean on the cooler shoulders of the year. Sow from March or April and again from late August into September, when leaf coriander romps away and is far slower to flower. For high-summer sowings, give the plants some afternoon shade (more on that below) and accept that they will need replacing more often.

2. Dry roots

Coriander has a long taproot and hates drying out. Let the compost or soil go dry — even once, in warm weather — and the plant reads it as a sign that conditions are turning against it, and bolts. This is the cause people most often miss, because the trigger happened days before the flower stem appeared.

The fix: keep the roots consistently moist, never bone-dry and never waterlogged. Pots dry out fastest, so check them daily in summer; a deeper pot holds moisture better than a shallow one and gives the taproot room. Ground-grown coriander copes better but still wants watering in dry spells.

3. Transplanting — it hates root disturbance

Coriander resents having its roots disturbed, and the check it gets from being moved is enough on its own to send it straight to seed. Plants raised in modules or bought as a pot from the supermarket and split up will often bolt within days of going out, no matter how careful you are.

The fix: sow direct, into the pot or ground where the plants will stay, and thin rather than transplant. If you must start under cover, sow into deep modules or root-trainers and plant out the whole undisturbed plug while it is still small. This single habit prevents more bolting than anything else.

4. The wrong variety

Ordinary coriander sold simply as "coriander" is often a seed-coriander type, bred to flower and produce plenty of seed quickly — exactly what you do not want if you are growing it for leaf. Sow that on a warm day and it will bolt fast whatever you do.

The fix: buy a named, bolt-resistant leaf variety. 'Calypso' and 'Confetti' are slow to bolt and produce a long run of leaf, and 'Leisure' is another reliable leafy type. The seed packet will usually say "slow to bolt" or "leaf coriander" — look for that wording.

5. Crowding

Plants growing shoulder to shoulder compete for water, light and root room, and that low-level stress nudges them towards flowering sooner. A dense, overcrowded sowing tends to bolt as one.

The fix: thin seedlings so each plant has a little space — a few centimetres between plants is plenty for leaf coriander grown as a cut-and-come-again crop. Thinnings are not wasted: the young leaves are perfectly good to eat.

How to grow leafy coriander that lasts

Put the fixes together and you have a simple recipe for a steady supply of leaf. None of it is difficult — it is mostly about removing the stresses above before they happen.

Choose a bolt-resistant leaf variety. Start with the named types above rather than generic coriander. It is the easiest single change you can make.

Sow direct and thin, don't transplant. Sow thinly into a deep pot or straight into the ground, water gently, and thin the seedlings rather than moving them. This sidesteps transplant shock entirely. If you are growing on a windowsill or balcony, a deep container of peat-free compost works well, and the same no-transplant rule applies.

Keep the moisture even. Consistent watering is the difference between weeks of leaf and a fortnight before it shoots. Don't let pots dry out in warm weather, and water the ground in dry spells. For more on getting a long, even run of cutting, see the full method in the coriander guide.

Give it light shade in summer. Coriander welcomes a bit of relief from the strongest midday and afternoon sun once the weather warms up. Tuck summer sowings behind taller plants, or grow them where they catch the morning sun but are shaded later — a spot that also suits lettuce and other cool-season leaves. Cooler roots and a little shade hold off flowering noticeably.

Sow little and often. This is the real secret. Because every coriander plant will eventually bolt, the trick is to always have a younger one coming on behind it. Sow a short row or a small pot every two to three weeks through the growing season — a method called successional sowing — so there is never a gap. There is a full schedule in our guide to successional coriander sowing, which is the partner article to this one.

Treat coriander as a quick, repeatable crop rather than a single plant you nurse all season and it stops being frustrating. It is one of the easiest crops for beginners once you accept that bolting is built in and simply sow around it.

Making the most of a bolted plant

A coriander plant that has bolted is not a write-off — leave it in the ground and it earns its keep in two more ways.

The flowers feed pollinators. Those clusters of tiny white flowers are a magnet for hoverflies, bees and other beneficial insects, whose larvae help keep aphids down elsewhere on the plot. Letting a plant or two flower is genuinely useful if you are also growing pollinator-friendly plants, and it adds a bit of froth to a border for almost no effort.

The seed is two crops in one. The unripe green seeds have a bright, citrusy coriander flavour and are lovely scattered into salads or pickles. Leave them on the plant and they ripen to the round, tan seeds you buy as the spice — pick them once they turn beige and dry, before they scatter. A few left to fall will often self-sow a free patch for next year.

So even a plant that got away from you delivers flowers for wildlife and seed for the kitchen. With the leaf, that makes coriander a genuine three-in-one herb — you just have to decide which crop you are growing for each time you sow. For everything from variety choice to harvesting, head back to the full coriander growing guide.