Top of The Crops - Coriander

Growing Coriander In A Polytunnel

Coriander, Coriandrum sativum, is a useful herb or spice to grow at home. You can grow coriander either for the leaves, known as cilantro in the US and elsewhere, or for the coriander seeds, typically used in curries and other recipes as a spice. 

Coriander is a herb that can be a great addition to a polytunnel in a garden or as part of a commercial enterprise. The plant is known for its pungent leaves, which are not to everyone's taste, and for its round seeds, which are also used in a range of curries and other recipes. You should choose the correct variety – one that is best for leaves or best for seeds.

There are chemicals in coriander that have a fresh citrussy zing to some people but to others, give this plant a nasty astringency and soapy taste that is anything but appealing. 

Personally, like around a quarter of people, I cannot stand the taste of coriander leaves. (It turns out that this is a genetics thing.) However, I have grown coriander for its seeds, which can be used in a number of ways that are more appealing to me, such as in the spice mix garam masala. 

The Preferred Conditions for Coriander

To grow coriander it is important to make sure that you provide the right growing conditions. That means making sure that coriander has:

  • Full sun for seeds or light/partial shade for leaves. 

  • Moist but well drained or well drained fertile soil or growing medium. 

Coriander is an annual crop but in the right conditions it can sometimes self-seed and spring up over multiple years in a polytunnel garden. You can also grow it outdoors in other parts of your garden. 

Coriander can be grown in polycultures alongside other herbs, among edible and ornamental flowers, or as a companion plant for other crops in a vegetable plot or other food-producing garden.

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What You Will Need to Grow Coriander

To grow coriander you will need:

  • Coriander seeds.

  • Seed trays, seed starting potting mix etc. if sowing indoors. 

  • A suitable growing location.

  • Facility to water your coriander.

  • Organic matter for mulch/ feeding. 

How to Grow Coriander

If you want to grow coriander at home then you will obviously need to decide where exactly to do so. You can grow coriander for a short period of time indoors if you wish, but longer term, these plants will typically need to be placed outside. 

Coriander can be grown in a polytunnel but note that it is likely to bolt more quickly in warm conditions, so if you want a leafy harvest this may not always be the best choice. 

Sowing Coriander

Once you have chosen your coriander, and decided where you place it, you can either sow in containers inside from April, perhaps even as early as February or March, or direct in the soil between June and September.

Sowing indoors will give a much earlier crop of coriander. Germination rates are usually reasonably high, and you can prick out and pot on seedlings before hardening them off and planting them into their final growing positions once they are around 15cm tall, when there is no longer a risk of frost in the planting area. 

Sowing Outdoors

Sowing coriander at the right time can help to reduce the chances of a plant grown for its leaf going to seed prematurely. Make sure you do not sow while there is still risk of frost – wait until after the last frost date in your area and check the weather forecast. 

Coriander seeds are large and relatively easy to sow. You can broadcast them over the surface of the soil or potting mix of your chosen planting location, or sow them in shallow drills, and then cover them over lightly with soil or compost. Water them in and wait. Germination should usually occur within 1-3 weeks. 

Seeds are best sown every 3-4 weeks in batches if you want to be able to harvest the leaves. If you do so, you can expect near-constant harvests from the middle of summer onwards. 

If you are trying to grow coriander seeds than you should sow in spring or early summer to give the plants the time to complete their lifecycles and produce ripe seeds. Once seedlings emerge, those grown for seed should typically be thinned to leave a spacing of around 10cm between plants. 

Harvesting Coriander

If you are harvesting the leaves then these are best harvested when young. They can be used fresh or frozen for later use. The harvesting can begin as early as July and with the right varieties you can be picking fresh coriander leaves right through until the autumn.

If you are harvesting the seeds then these can be ready for harvest, usually, from late summer onwards. After flowering, the coriander plants will go to seed, creating seed pods filled with round, ball-like seeds that are around the size of pepper corns. 

Cut the stalks as soon as the pods are ripened and just before they fall to the ground. These can then be dried on paper sheets or in a paper bag. Leave the seeds to fully ripen before separating them from the rest of the stalk and letting them dry out entirely before storage. 

Storing Coriander

Use fresh leaves of coriander as soon as possible after harvesting, they will last only a short length of time. You can also freeze fresh coriander for use in cooked recipes later in the year, finely chopped and frozen in cubes with water or oil. 

Store the fully dried seeds in airtight containers. The seeds can be used whole in recipes or ground into a fine powder using a mortar and pestle.

Care Tips for Coriander

Coriander is not at all challenging to care for as long as you have provided the right growing conditions for these plants. 


It is important to keep the soil around plants moist but you should also be careful not to overwater. If the roots dry out or are swamped, this can cause the plants to bolt or flower prematurely, which will reduce the quantity of leaves that can be harvested if this is the yield you are going for. 

Make sure that excess water can always drain away freely, and try to water the soil at the base of the plants and keep the foliage dry. 


Coriander does not typically need feeding when grown in the ground. However, if you are growing in containers or growth seems poor, you may consider providing an organic liquid plant feed with relatively balanced NPK profile.


Coriander does not like too much competition and so you should weed regularly around your coriander in order to prevent any check to growth of the plants.

Removing Flowers

If you are growing coriander for the leaves rather than the seeds then removing the flowers will prolong your harvesting period somewhat. Remove any flowers as soon as they form so that the plant focusses its energy on foliage growth rather than on flowering and seed production. 

Remember that these flowers are actually as edible yield in their own right, and can potentially be added to salads to prevent waste. 


Ripe coriander seeds can be collected at the end of the growing season not only for use in the kitchen but also for sowing in the garden to propagate your plants. Coriander seeds that are allowed to develop and drop to the soil can also self-seed, so new coriander plants pop up in your garden the following year. 

Varieties of Coriander

Named cultivars of coriander to grow in a UK garden include:

  • 'Calypso' – British -bred, slow to bolt, can be cut back and harvested 3 times over summer.

  • 'Chechnya' – A reliable eastern-European variety. 

  • 'Confetti' – variety with carrot-like, divided foliage

  • 'Cruiser' – quick cropping , compact variety with large, shiny leaves. 

  • 'Leaf Leisure' – a slow to bolt variety producing plenty of foliage.

  • 'Lemon' – a standard-looking type with citrus-scented leaves.

  • 'Santo' – an established traditional variety with excellent leaf production. 

  • 'Topf' – another long established variety highly regarded by UK container growers.

Common Problems for Coriander

Coriander is not generally prone to serious issues,  but you can experience a range of problems with pests, and when the conditions are not quite right bolting can often occur, which is of course not desirable when you are trying to cultivate coriander for its leaves. 

Aphids and Other Pests

While aphids and other pests like slugs and snails can sometimes pose a problem for coriander plants, especially while they are young, careful organic gardening practices can help you make sure that pest problems like these rarely become serious issues. 

Boost biodiversity by companion planting and create habitats for beneficial wildlife in your space to make sure that no one pest species can get out of control. 


A range of different environmental issues – especially relating to temperature and water – can cause coriander plants to flower prematurely – or bolt. Bolting is common with coriander and the key thing you wish to avoid if growing coriander for its leaves. 

Choosing the right place to grow coriander and providing the right care can often help you avoid this issue. 

Top Tips for Growing Coriander in a Polytunnel

Growing coriander in a polytunnel may be challenging for earlier sowings, which can easily bolt in warm conditions. 

But polytunnel growers can consider later sowings, and can then potentially harvest leaves right through autumn and even into early winter, so a polytunnel can dramatically extend the growing season. Of course, growing coriander for seed will be much easier in a polytunnel garden. 

Using coriander as a companion plant for other polytunnel crops throughout the growing season may be an excellent idea.

Coriander plants can attract beneficial predatory insects to your polytunnel and it is suggested that planting coriander close to cabbages and other brassicas may reduce the incidence of pests in those plants. 

By attracting hoverflies, coriander may also be beneficial as a companion plant to a whole range of crops.


What Is The Secret To Growing Coriander?
Why Is Coriander Hard To Grow?
How Do You Take Care Of A Coriander Plant?
What Month Do You Plant Coriander?


Raman, R., (2023) Cilantro vs Coriander: What's the Difference? Healthline. [online] Available at: 

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crowing coriander in a polytunnel