Forming a fountain of slender arching foliage, lemon grass thrives in warmth and full sun. This tropical herb is best grown in a pot, so it can be moved indoors over winter. The lemon-flavoured stem bases are widely used in cooking.
Lemongrass - Cymbopogon citratus
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Lemon grass (Cymbopogon citratus) is a popular ingredient in Asian and especially Thai cuisine – it’s a tropical grass, originally from India, so isn’t hardy in the UK and needs protection from frost. It is ideal for growing in a container that can be placed in a warm, sunny spot in summer, then moved indoors over winter. If you don’t have space indoors over winter, simply treat it as an annual and grow fresh plants every spring.
Allowed to grow from year to year, lemon grass will form a large clump of narrow evergreen leaves up to 120cm (4ft) tall, coarse in texture and blue-green in colour. It’s the swollen stem bases that are used in cooking, taken from an established clump. These bring a rich citrus flavour to curries, soups and sauces, and can be infused to make a refreshing tea.
For more herb-growing tips and inspiration, see our guide to growing herbs and our guide to citrus-flavoured herbs.
What and where to buy
The most widely available lemon grass is Cymbopogon citratus, although you may occasionally find a more compact East Indian species, Cymbopogon flexuosus.
Lemon grass seeds can be bought in larger garden centres and from some online seed suppliers.
Young plants may also be available in spring and summer, mainly from specialist herb suppliers, or you can grow it from stems bought for cooking, sold in many supermarkets and Asian food shops if they have a little root.
Sow lemon grass seeds in small pots or modular trays in late winter or spring, then place in a heated propagator or on a warm windowsill at 20–25°C (70–75°F). Germination can take several weeks. See our step-by-step guide to sowing seeds indoors.
Keep the seedlings warm, well-watered and in good light, to ensure strong growth. Move them into slightly larger pots if necessary, once the roots show through the holes in the base.
Young lemon grass plants can be moved outdoors in early summer, once night temperatures stay reliably above 5°C (40°F). Acclimatise the plants gradually to outdoor conditions – see our guide to hardening off. Alternatively, in cooler locations, keep lemon grass in a warm, bright conservatory all year round. To grow well and thrive, it really needs temperatures reliably around 13oC.
Lemon grass is best planted in a container, so it is easy to bring indoors in autumn to protect it from winter cold and wet. You can also plant it in the ground, and either treat it as a short-term annual herb or pot it up in autumn and bring it indoors.
To plant in a container, choose a pot about 30cm (1ft) wide and fill with a peat-free multi-purpose compost, then plant one or two young lemon grass in the centre. Place the pot in a warm, sheltered, sunny location.
To plant the ground, choose a site in full sun with fertile, free-draining soil. Space plants at least 30cm (1ft) apart.
Lemon grass needs little maintenance if grown in a sunny, sheltered site over summer, watered regularly and kept warm indoors over winter.
Water lemon grass growing in a pot regularly, as the small amount of potting compost will dry out quickly, especially in warm weather.
Newly planted lemon grass in the ground should be watered frequently in the first few months, after which it should only need extra water in dry spells.
Apply a thick layer of mulch, such as well-rotted manure or garden compost, around lemon grass growing in the ground, to help hold moisture in the soil and deter weeds.
As new growth appears in spring, feed plants in pots with a balanced liquid fertiliser once a week.
Lemon grass is tender, so bring it indoors in autumn, before overnight temperatures fall below 5°C (40°F) in your local area. Cut back the top growth if necessary, then place it in a bright, cool position and reduce watering, keeping the compost just moist. Lemon grass won’t usually survive outdoors in UK winters, even in mild areas, and an unheated greenhouse is likely to be too cold as well.
To make more lemon grass plants, simply divide clumps in spring. Tip the plant out of its pot, then use a knife or sharp-bladed spade to cut the rootball into two or more pieces, each with a good set of roots and several strong stems. Replant each section into its own pot and water in well.
Pruning and Training
Remove any tatty or faded foliage on an ongoing basis to keep plants looking their best.
Cut all the leaves down to 10cm (4in) from the base in autumn, and they will resprout in spring. This is useful if you’re short on indoor space over winter. Alternatively, cut back in early spring, before new growth starts.
There are two harvesting methods:
Select suitably thick stems from the outside of the clump and cut or pull them off as low down as you can, so you get as much of the swollen base as possible
Tip the plant out of its pot and remove a clump of stems by cutting through the rootball with sharp knife. Separate out as many stems as you want, then replant the remainder
Prepare the stems by trimming off the coarse stringy leaves, retaining only the lower 8–10cm (3–4in) for use. They should look like the stems you buy in the shops. The base of the stems can then be sliced or chopped into fish and meat dishes, especially curries, or used in sauces to add a citrus flavour.
Lemon grass is best used fresh but can be kept in the fridge for a week or so.
The leaves are too coarse to be used in cooking but can be infused to make a refreshing lemony tea.
Be sure to bring plants indoors into a heated location over winter. These tropical plants need at least 5°C (40°F) and are happy in centrally heated homes if given plenty of light. An unheated greenhouse will be too cold for them over winter.
Rust can occasionally affect the leaves, and plants grown in a greenhouse are susceptible to whitefly.
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