Coriander sowing without bolting: continuous harvest

Coriander is a tricky herb. You pick the first tender leaves, and before you know it, the plant is already flowering. A few warm days are enough to lose it to flowers and seed. You prevent that with the right spot, the right timing, and a smarter way of sowing.

What many gardeners do not know: coriander does not want the same conditions as basil. Where basil demands heat and full sun, coriander is happy with partial shade and cool weather. Give it what it wants, not what you assume it needs. Sow it in small batches and you will have fresh green leaves from June right through to October.

Why does coriander bolt so fast?

Coriander (Coriandrum sativum) is an annual herb from warm regions. Here it only gets one summer to set seed, so as soon as it gets warm it rushes toward flowering. With an ordinary variety you can already see flower stalks from around day 35.

This happens faster in full sun than in partial shade. Place your coriander somewhere that gets shelter in the afternoon and it will flower weeks later, giving you a longer harvest of fresh leaves.

Temperatures above 20 degrees clearly speed up bolting. On a hot day in July or August, the plant itself can sit at 25 to 30 degrees, which is too warm. May, June, and September into mid October, with temperatures around 12 to 18 degrees, are your best sowing months.

Varieties: leaf coriander or seed coriander

Seed suppliers separate varieties bred for leaf from varieties bred for seed. For the kitchen you want leaf coriander: it grows fuller, stays in leaf longer, and flowers later.

Two varieties sold by almost every seed supplier in Belgium and the Netherlands are 'Calypso' and 'Santo'. Both were bred to bolt more slowly than ordinary coriander, with full, tender leaves. With the right spot and timing, they give you 5 to 7 weeks of leaf harvest per sowing instead of 2 to 3.

Seed coriander, often sold simply as "coriander" or "coriander seed" with no variety name, is bred for a high seed yield. It flowers sooner and gives fewer leaves. Choose it only if you mainly want seed for the kitchen, not if you are after a long leaf harvest.

Location: the east side is worth gold

This is the most overlooked piece of advice for coriander. Do not put it in full, all-day sun. Look for a spot that gets morning sun but shade in the afternoon, between noon and four, such as the east side of a wall, fence, or hedge, or a spot under tall trees with light, shifting shade.

Why does that matter? Full sun can push leaf temperature up to 30 to 35 degrees on a hot day. A spot with afternoon shade keeps it around 18 to 20 degrees, and that difference can mean weeks before the plant decides to bolt.

Keep the soil a little moister in partial shade too. In full sun, moisture evaporates faster and the plant gets stressed, and a stressed plant flowers sooner. Not sure your garden has a spot like that? On gardenworld.app you can see exactly where that afternoon shade falls, in an example built from a photo of your own garden.

The sowing strategy: every three weeks, a little at a time

This is the real secret against bolting: never sow everything at once. Sow small batches every three weeks from early May to early September. That way you always have a new batch coming up, and nothing flowers all at the same time.

A workable schedule for partial shade:

• Early May: first sowing, a small strip of about 1 gram of seed
• Late May: second sowing
• Mid June: third sowing
• Early July: fourth sowing
• Late July: fifth sowing
• Mid August: sixth sowing
• Early September: last sowing, for harvest into October

Each sowing gives you around 3 to 5 weeks of leaves. Sow straight into the spot where the plant will grow, not into trays: coriander has a long taproot that does not like being moved. Make a groove about 5 mm deep, scatter the seed with 2 cm between seeds, cover lightly, and keep moist.

Pre-soaking: avoiding mould

Coriander seed is hard and germinates slowly and unevenly, sometimes only after 10 to 16 days. On wet sowing soil, mould can take hold in that time. Pre-soaking speeds up germination and makes it more even.

Soak the seed 12 to 18 hours in lukewarm water, drain it, then spread it out to dry lightly, not completely. That way it germinates in 5 to 8 days instead of 10 to 16. Pre-soaking is an extra step, not a requirement: sowing dry seed directly also works, just more slowly.

Water: moist, never waterlogged

Keeping it moist is the whole trick. From sowing until the seedling appears, usually after 5 to 10 days, the soil needs to stay evenly moist. After that, moist beats waterlogged: soil that is too wet brings mould and damping off in young seedlings.

Water with a rose on the can or a drip hose, not a hard jet from above, which splashes soil onto the leaves and invites mould. Once seedlings are up, water whenever the soil feels dry 2 cm down. In high summer that can mean daily, in partial shade or autumn often just a few times a week.

Thinning and picking

Once seedlings are about 5 cm tall, thin them to 10 cm apart, removing the weakest and leaving the strongest. That gives each plant room to grow full leaves.

After thinning you can pick for the first time, carefully. Stop before July, though: picking in the height of summer stresses the plant further and speeds up bolting. From August, once it cools down, you can pick again, and the same plant will still give you 3 to 4 more weeks of leaves.

Common mistakes

Too much shade: coriander still wants light, just not the full midday sun. With less than 4 hours of direct light a day it grows long, thin, and floppy.

Sowing everything at once: then everything flowers together, and you are left with nothing for weeks. Sow small batches instead, every three weeks.

Full sun in summer: this makes the plant bolt in as little as 30 to 35 days, far too early for a decent leaf harvest.

Soil that is too wet: brings mould and seed rot. Keep it moist, never waterlogged.

Skipping thinning: plants crowded too close together stay small and weak and bolt sooner.

Seed harvest: recognising ripeness

This is the reward at the end. By late October your last sowings will have flowered and set seed. Coriander seed looks like two small ribbed balls stuck together.

Seed is ripe once it turns from green to yellow-brown and feels hard. Cut the whole flower stalk, put it in a paper bag, and hang it somewhere dry, such as a garage or attic. After 2 to 3 weeks the seed falls out on its own.

Store the seed in a sealed jar or envelope somewhere dry and it stays viable for about two years. Homegrown seed is often better suited to your garden and climate than shop seed, simply because it has already grown there once.

Step by step

Step 1: Pick a spot with afternoon shade

Look for a corner that gets shade between noon and four in the afternoon: the east side of a wall, fence, or hedge is ideal.

Step 2: Prepare the soil and sow

Make a groove 5 mm deep and scatter the seed with 2 cm between seeds. Pre-soaking in lukewarm water for 12 to 18 hours is optional, not required.

Step 3: Keep it moist until it germinates

Cover the seed lightly and keep the soil evenly moist, never waterlogged, until the seedling appears.

Step 4: Repeat every three weeks

Sow a new, small strip every three weeks from early May to early September.

Step 5: Thin and pick from August

Thin to 10 cm apart once seedlings reach 5 cm. Pick carefully from August, not during the height of July heat.

Step 6: Let the last sowing set seed

Let the final sowing flower and set seed. Harvest once it turns yellow-brown and dry it in a paper bag.

Frequently asked questions

Why does my coriander always bolt by June?

You probably sowed seed coriander in full sun. Choose a leaf variety like 'Calypso' or 'Santo', place it in partial shade, and do not sow it all at once. That gives you green leaves from August into October.

Can I sow in autumn for a winter harvest?

No, that will not work here. Below 10 degrees coriander stops growing, even if the seed still germinates. Sowing only makes sense from March to early September.

Can I use seed from the shop?

Yes, that works fine. Seed you harvested yourself is often a little better suited to your garden, because it has already grown there once.

Can I sow coriander together with other herbs?

Yes. Parsley grows well next to coriander, since both like partial shade and sowing in small batches. Keep basil elsewhere, since it wants full sun.

See it in your own garden first

Have your own garden space and want to see first how coriander and other herbs fit into it? Upload a photo of your garden to gardenworld.app and view a free example of a new design with your herb corner. The sharp image with plant list costs 7,99 euro, once only, no subscription.