If you love Indian cuisine then you may wish to grow curry leaves in your polytunnel for at least some of the year. These are not the easiest thing to grow, as they are not suited to our temperate climate and require some coddling. But with protection, you can certainly grow this plant here in the UK.
Curry leaves, as used in Asian cookery, are from the shrub or small tree known as Bergera koenigii, also known as Murraya koenigii.
This subtropical or tropical species grows up to around 4.5m tall with a spread of around 3m. Native to the Indian subcontinent, this species is in the rue family, which also includes rue, citrus and satinwood. It has been used within Tamil culture since at least the 1st century CE.
Though this is not a plant that can be grown outdoors in the UK year-round, it is possible to overwinter it indoors or in another frost-free location and to place it outside or in an unheated polytunnel over the summer months.
It is important to note that these are not the same as the 'curry plant' Helichrysum italicum, which has a strong curry smell but is not edible.
Note too that curry leaves are not an ingredient in curry powder (though other 'curry' spices may also be grown in a polytunnel garden).
Curry leaves are used in Asian recipes in much the same way as bay leaves are used in other cuisines. They are used to add aromatics to a dish, fried in ghee and added to curries, or dried, powdered and used in spice blends. They also have a number of medicinal applications.
Curry leaves are not the easiest plants to establish. They are commonly grown from seed but it can take 1-2 years for the plants to become established. Pinching and pruning while the plants are young is important as it will help to create a bushier plant that is good for harvesting. Removing the hard outer casing from the seeds will help them to germinate more quickly – always use fresh seeds.
Of course it is also possible to buy your curry leaf plants online or from some local plant nurseries. Do make sure that you get the correct plant, Bergera koenigii, and not Helichrysum italicum which is known as ' curry plant'.
It is easiest, whether your curry leaves are grown from seed or purchased, to grow them in containers, so these may be moved as you require to a suitable location for the seasons. Make sure that the container you choose is large and sturdy enough for these fairly large plants. Fill it with a suitably free-draining and yet reasonably fertile potting mix.
Since the plants will usually be grown in containers, you must make sure that the plants get enough to eat. Fertilise your plants every five weeks or so with a good, organic fertiliser.
Curry leaf can either be grown from seed or from semi-ripe cuttings. However, for UK growers the simplest option will be to just purchase a potted specimen from a plant nursery or houseplant vendor. Home propagation will be challenging and special equipment such as a heated propagator will usually be required to grow from seed.
The seeds of the curry leaf plant are the pips at the centre of the red fruits that form on the tree. Growing these trees from seed is possible, though you do need to start with viable, fresh seeds and should note that older seeds will not tend to germinate successfully.
It is also important to note that even if you are successful in germinating the seeds, it will still be at least a couple of years until you can begin to take a harvest of leaves from your new plant.
If you purchase or collect fresh berries, these need to be soaked for 24 hrs to extract the seed within each one. After they have been soaked, the flesh can gently be rubbed off the seed. If the seeds are older, roll or rub the berries between your hands to remove the tough outer casing.
Once you have extracted the seeds, these are sown around 1cm deep in containers of moist potting mix, ideally covered for propagator conditions. A heat mat or heated propagator may make the job easier since germination requires the medium to be at a temperature above 20 degrees C.
If the seeds are viable and the right conditions have been provided then the seeds should germinate within 2-3 weeks.
Once seedlings emerge, these can be pricked out and potted on into their own individual containers. Pot up as required and then move outdoors or to an unheated polytunnel if you wish once daytime temperatures remain consistently above around 18 degrees C.
These trees/ shrubs can also be propagated using semi-ripe cuttings taken in the late spring or summer. To take a semi-ripe cutting:
Select a healthy branch with at least three sets of leaves. Cut off the branch you have selected as close to the main stem or trunk as possible, trim it to a 45 degree angle. Remove the lowest set of leaves and dip the base of the cutting in rooting hormone for best results.
Insert the cutting or cuttings into the edge of a pot filled with a suitable cuttings potting mix. Place this pot into a sunny location where it remains warm, and where it gets at least 6 hours of sunshine each day.
Mist to maintain humidity and keep the medium moist, and after around 3 weeks tug gently to check for rooting. When the cutting has rooted successfully, it will be firm in the growing medium.
Once established the new plant can be placed outdoors, hardened off gradually, as long as the nighttime temperatures are above around 5 degrees C.
To grow curry leaves the most important thing is to understand the conditions that this plant requires. Remember that this is a tropical or subtropical plant, and requires plenty of warmth and full sun.
Providing temperatures that are sufficiently warm is one of the most challenging, and also most important, aspects of the care of this plant. You also need to think about the soil, which should be loose, rich, free-draining and slightly acidic with an pH, ideally, between 5.6 and 6.
When it comes to water, it is better to keep the plant on the dry side. These trees / shrubs tolerate semi-drought conditions once they are established and they can cope better with conditions that are too dry than with those that are too wet. This is one reason to place one in a polytunnel rather than outdoors, where British summer weather often leaves a lot to be desired.
Water only infrequently through spring and summer and let the soil dry out before watering again. Water deeply each time you do water but make sure that water can drain away freely from the base of the container. Feed with a general purpose organic liquid plant feed every few waterings through the growing period, between April and early September. In winter, watering should be only minimal and feeding should be ceased.
You can start harvesting a few leaves from your plant once it has become established and reached a sufficient size to cope with the harvesting. The fresh leaves are best so aim to harvest leaves as close as possible to the time you wish to use them.
If the bush flowers and berries form, it is best to pick these off to encourage leaf production to continue. However, these are also edible, with a peppery flavour.
This tree/ shrub is in RHS pruning group 1. It usually requires little to no pruning as it naturally forms a well-balanced framework of branches.
Bergera koenigii is usually sold by its species name alone. But there are cultivars in three distinct sizes.
Most store-bought curry leaves come from the largest of the three, but some of the dwarf and miniature types are best for home growers. Just make sure that you choose a cultivar that is suited to culinary use, as not all have the most impressive flavour profile.
When grown under cover, curry leaves can succumb to a number of common infestations that can arise when we are growing in a greenhouse or polytunnel setting. For example, they can encounter issues with scale insects, aphids, mealy bugs, and red spider mites. Remain vigilant so that you can nip any potential problems in the bud.
Aside from best issues, these plants can also have issues if you do not get it right when it comes to providing the right growing conditions and care. Remember, problems will arise if temperatures drop too low – or rise too high through the summer months. And the plants can suffer if waterlogged conditions arise.
Curry leaf is prone to iron deficiency so look out for this, and add iron sulfate if necessary if the leaves are yellowing, with dark green veins. Other nutrient deficiencies may also occasionally arise.
Usually, the curry leaf will be kept in a pot rather than a bed or border so that it can be moved easily. Make sure that your pot size is practical and that you can move it when needed from A to B.
Take steps to heat your polytunnel in winter if you wish to keep this plant in there year-round.
Additional protection for the plant may also be required in the shoulder seasons.
Make sure the space is well-ventilated but that humidity does not drop too low when growing curry leaves or pest problems like red spider mites may become more likely.
Consider growing other ingredients to help you cook the curries and other recipes that you love to make – including spices like ginger, cumin and turmeric, coriander seeds... chilli peppers... onions, garlic, and a wide range of other delicious home-grown veg.
Desk, S., (2023) 7 Uses Of Curry Leaves In Indian Cooking: Flavours And More. Slurrp. [online] Available at: https://www.slurrp.com/article/7-uses-of-curry-leaves-in-indian-cooking-flavors-and-more-1696443257772
