Stop blaming yourself for bolting coriander.

Coriander bolts, which means it runs up to flower and seed, when the weather warms, the days lengthen and the soil dries, and it goes faster if its roots have been disturbed. It can happen even with good care. Sow it direct where it will grow, choose a slow-bolting variety, sow a pinch every two to three weeks, give it afternoon shade as the heat arrives and pick it young. Lettuce plays by the same rules.

The coriander was lovely for three weeks. Then one warm week, a stem shot up out of the middle, the leaves went thin and feathery and the flavour went with them. An unexpectedly short harvest is genuinely frustrating. It is also not a mark against you. It is a coriander plant doing what a coriander plant does when spring turns.

Once you know what sets it off, you can adjust how and when you sow and how you look after it, and stretch the picking further into the warm months.

What bolting actually is

Bolting is the plant switching from growing leaves to producing flowers and seed. For an annual herb it is the whole point of its life, and coriander is quick to make the switch. Rising temperatures and dry spells push it, long days can push it too depending on the type, and stress hurries it along, especially the shock of being dug up and moved.

It is a survival response, not a fault. The plant reads warmth and dry soil as the season closing and sets seed before it is too late. Once the switch is thrown it does not reverse. Pinching out the flower stem buys a little time, not a season.

Why the punnet from the nursery bolts first

Coriander grows a taproot and it resents having that root disturbed. A seedling lifted from a punnet and planted out often bolts soon after, because disturbing that root is one more stress the plant can read as the season closing. Young transplants can succeed, and plant age, root disturbance and the weather all play a part, but this is one of the most common reasons a first coriander crop disappoints.

The fix costs nothing: sow the seed where the plant will live. Straight into the bed, or straight into the final pot. Coriander seed is large enough to handle easily and it comes up in one to three weeks in spring soil.

Choose a slow-bolting variety

Some varieties hold their leaf longer in warm weather. Gardening Australia names 'Slow Bolt' and 'Fine-leafed Confetti' as the ones for backyards. Neither is immune. What they give you is more time once the weather warms, and that is often the difference between a garnish and a harvest.

Sow a pinch, not a packet

One big sowing gives you a whole batch that matures together and tends to bolt around the same time. A pinch of seed every two to three weeks gives you a short row coming on as the last row flowers, and that rhythm is how people keep coriander on the bench through to early summer.

A row does not have to be long. A short row, sown thinly, gives a run of picking, and the next short row takes over as it starts to stretch.

Shade, water, and the pick-young habit

Heat and dry soil are the two triggers you can soften. As spring warms:

• Give coriander the morning sun and afternoon shade. The east side of a taller crop works, so does a square of shade cloth on the hot days, so does moving a pot.
• Keep the soil evenly moist. A bed that dries to a crust between waterings is a bed that bolts early.
• Pick the outer leaves young and often. Picking is unlikely to hold off bolting on its own, but it means you get the leaves before they change.

In Perth and Adelaide, where the spring heat arrives dry and early, shade and steady water do more work than anywhere else. In Brisbane, humid air slows how fast the soil dries but does not water the roots for you, so keep checking the soil and hold the moisture even, and let the shade do the rest.

When it bolts anyway, let it

A bolted coriander plant is not a failure, it is the second crop. The small white flowers bring hoverflies, lacewings and ladybirds into the patch, along with the bees, which is worth having next to your tomatoes and zucchini. The green seed that follows has a bright, citrus flavour and is a spice in its own right, and the dried seed is the coriander of the spice rack. Save a spoonful for next season, or simply let a few plants drop it and thin the volunteers.

Lettuce plays by the same rules

Lettuce bolts for the same reasons, warmth and long days, and it tells you by growing a tall centre and turning bitter. The heat, moisture and little-and-often parts carry across, though unlike coriander lettuce transplants happily, so it is just as often raised in trays and planted out. Sow a little every fortnight, move summer sowings into part shade, keep the water even, and pick loose-leaf types as baby leaves before the heat gets to them. Wild rocket, the perennial type, holds on longer than the fast salad rocket, so sow salad rocket in pinches for a steady supply.

A note for every zone

The triggers are the same everywhere; the calendar is not.

• Brisbane, Gold Coast, Sunshine Coast: coriander can be sown in any season except summer here. Spring sowings run shorter as the heat builds, so keep them in afternoon shade and expect a quick turn; autumn and winter give the longest run.
• Sydney, Newcastle, Wollongong: sow in pinches from early spring to early summer.
• Perth and Adelaide: the same, but the window closes sooner because the dry heat arrives early. Sow through spring and lean on shade and water.
• Melbourne, Geelong, Canberra, Hobart: spring is a good stretch for coriander here. Sow direct every few weeks through to early summer, after which soil warmth starts to work against you.
• Darwin, Cairns and the tropics: a dry-season crop, sown through the cooler months rather than in spring.
• Alice Springs and the inland: autumn to spring, with shade and steady water as soon as the days warm.

Your postcode picks the chart on our What to Sow Now page if you want the month-by-month version.

Grow it: seeds for this lesson

Seeds that suit the method.

Coriander Slow Boltthe variety named for the job. Sow direct, a pinch at a time.See the seedsCoriander Confetti Frillyfine-leafed and slower to run, with a softer leaf for salads.See the seedsRocket Wilda peppery, slower-to-run rocket. Pick it young and often through the warm months.See the seedsLettuce Salad Bowl Greena loose-leaf lettuce to pick young through the warm months.See the seeds

Sow it where it will grow, sow it small and often, shade it when the heat comes and pick it young. That is the whole correction, and it can turn coriander from the herb that always fails into one that is on the bench for much longer. For the wider list of what to sow in your area in any month, our What to Sow Now page covers the rest of the bed.

Frequently asked questions

Can I stop coriander bolting once it starts?

Not really. Pinching out the flower stem slows it a little, but the plant has already switched over. Pick what leaf is left and let the next sowing take over.

Is bolted coriander safe to eat?

Yes. The leaves are thinner and the flavour changes, which is why most people stop picking them. The flowers, green seed and dried seed are all used in the kitchen.

Why does coriander in a pot bolt faster than in the ground?

Pots warm up and dry out faster than a bed, and both are triggers. A larger pot, a shaded position and steady water all help.

Should I fertilise to stop it bolting?

Feeding is not the main lever. Warmth and moisture matter far more, though a well fed, unstressed plant is less likely to be pushed into early flowering, and Gardening Australia's own advice for avoiding bolting includes keeping seedlings well watered and regularly fed.

Can I grow coriander through a Sydney or Perth summer?

It is hard. Slow-bolt seed, afternoon shade and quick succession sowings give you short runs of leaf. Some gardeners switch to sawtooth coriander, also called culantro (Eryngium foetidum), which handles heat and has a similar flavour. It wants shade and moist, well-drained soil, rather than a pot left standing in water.

Can I save the seed from a bolted plant?

Yes. Let the seed heads dry to brown on the plant, rub them into a paper bag, and store the seed cool and dry. It is the same seed you would sow next autumn or spring.