RHS Growing Guides
How to grow citrus
Our detailed growing guide will help you with each step in successfully growing Citrus.
Getting Started
What better way to add a Mediterranean feel to a sunny patio, doorstep or balcony than with a citrus tree? They usually form compact plants, either small trees or shrubs, ideal for growing in containers. Some, such as lemons, are suitable for beginners, others can be more of a challenge.
Growing citrus as houseplants is not ideal long term, as most prefer a cool spell in winter and a more humid atmosphere than centrally heated homes usually provide.
While citrus may not be the easiest plants to grow, if you can give them the right conditions they’ll reward you with fragrant white flowers, glossy evergreen leaves and juicy, tangy fruits. With some varieties, the sweet citrus-scented flowers appear all year round, while others flower in late winter. The resulting fruit ripen slowly, for up to a year, so plants often carry flowers and fruit at the same time, for double the appeal.
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Choosing
There is a huge range of citrus plants to choose from, including lemons, oranges, mandarins, limes, grapefruits, kumquats, limequats, calamondin oranges, tangelos, citrons, kaffir limes and more. Some varieties produce fruits that can be eaten straight off the tree, while others are just for cooking or for juice.
Most citrus form attractive small trees or shrubs less than 1.5m (5ft) tall, so are ideal for growing in containers. Some are trickier to grow than others, so check their needs carefully to ensure you can keep them happy. If you’re new to growing citrus fruit, it’s best to start with one of the easier types, such as lemons. Certain varieties of kumquats, limes and calamondin oranges can also be fairly straightforward.
Citrus plants aren’t generally hardy in the UK, even though some may be marketed as suitable to grow outdoors in a warm location. A few can tolerate temperatures down to 5°C/41°F (such as some lemons), but others need at least 13°C/55°F (such as calamondins). So they are best kept in greenhouse, conservatory, glazed porch or similarly bright frost-free location over winter, if not all year round. Make sure you have the right conditions for them before you buy.
If you’re considering growing citrus as houseplants, bear in mind that most don’t fare well long term in centrally heated homes, as the atmosphere is usually too dry and can be too warm in winter. A cooler conservatory or glazed porch may be a more suitable location.
What and where to buy
Some citrus plants may be available in larger garden centres, especially in summer, but for the widest choice, go to specialist suppliers, either online or in person. Specialist growers will also be able to offer more detailed growing advice, to help you choose the best fruits and varieties to suit your level of skill, growing conditions and available space.
Most commercially sold citrus plants are grafted to ensure they fruit at an early age. Ungrafted plants may take up to ten years to fruit, so make sure the plant you’re buying is mature enough to crop. The easiest way to be certain is to buy a plant that is actually in flower and/or fruiting.
Citrus plants can be expensive, so take care over your choice. Prices vary depending on the type of fruit, the variety, and the size and age of the plant. They are sold in pots, often in fruit for immediate visual impact.
Recommended Varieties
This variegated cultivar bears masses of orange fruits, 4cm (1.5in) wide. The plant is vigorous and the main shoots should...
Moderately vigorous, the large fruits have deep red, extremely juicy flesh, thin skin, and a very sweet flavour.
This bears dozens of small, oval fruits on compact plants. The balance of flavours between the sour flesh and sweet rind...
Planting
Citrus plants are usually sold in pots that are sufficiently large, so they shouldn’t need repotting for several years. It’s best not to plant them in the ground, as they aren’t fully hardy – keep them in a container so it’s easy to move them indoors over winter.
Repotting
Most newly bought citrus plants can be kept in their original pot for several years. But if you wish to transfer a plant into a different or more attractive container, choose one that is a similar size and try to disturb the roots as little as possible. The container should be only slightly larger than the rootball. Avoid moving citrus plants into a pot that is a lot larger, as this can hinder rather than help them.
Once the roots have filled the container and started appearing through the holes in the base, it’s time to move the plant into a slightly larger container. Do this in spring, and choose either a specially formulated citrus compost or a nutrient-rich soil-based compost, such as John Innes No 2, and mix in about 20 per cent sharp sand or grit to improve the drainage.
Plant Care
Citrus plants need regular care all year round, including watering with rainwater, feeding with citrus fertiliser and protection from cold temperatures.
Watering
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In summer, water citrus plants freely, ideally with rainwater. Containers can dry out quickly, especially in hot weather, so check the compost daily.
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In winter, when plants are indoors, allow the surface of the compost to partially dry out before watering, then water thoroughly with tepid rainwater, allowing the excess to drain away. Overwatering in winter is one of the commonest problems, so err on the dry side. And never leave pots standing in water, as this can cause the roots to rot. Yellowing of the leaves or shedding leaves can be signs of overwatering.
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Humidity is important too, especially if plants are kept in a heated environment. To raise humidity, stand the pot in a tray filled with gravel or clay pellets. Keep the water level just below the surface of the gravel, so the compost doesn’t get waterlogged. Grouping several plants together can also help to keep the air more humid. Misting plants may beneficial too – in summer, do it early in the morning to avoid scorching.
Feeding
Citrus are hungry plants and should be fed all year round. Use fertiliser specifically formulated for them:
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Apply summer citrus feed, which is high in nitrogen, from late March to October.
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Switch to a more balanced winter citrus feed from November to mid-March.
It’s also beneficial to remove the top 5cm (2in) of old potting compost annually in late spring and replace it with fresh compost.
Lack of nutrients can cause leaves to turn yellow or drop off, and prevent flowers or fruit forming.
Pollinating
Citrus plants are self-fertile, meaning you only need one plant for successful pollination. However, in winter when plants are indoors, you can improve pollination by raising the humidity – stand plants in trays of damp gravel and gently mist the flowers with tepid water. The flowers don’t need to be pollinated by hand.
Fruit thinning
Citrus trees have a tendency to produce more fruit than they can successfully support, so it’s usually best to reduce the number of young fruits to ensure the remaining fruits reach a good size and ripen well.
Most citrus trees about 1m (3ft) tall should be allowed to carry no more than 20 fruits at one time.
Kumquats, on the other hand, with their much smaller fruits and bushy style of growth, can successfully carry a heavy crop without any need for thinning.
Winter protection
A frost-free greenhouse may be suitable for some, but others may need warmer conditions, such as in a conservatory. A few lemons, for example, will be fine as low as 5°C (42°F), kumquats often need 7°C (45°F) or more, limes and grapefruits should be kept above 10°C (50°F) and calamondin oranges may need at least 13°C (55°F). Centrally heated homes are usually too warm in winter, and the air tends to be too dry.
Citrus plants should keep their leaves all winter, which means they require plenty of light, humidity and occasional watering and feeding. Many citrus flower in late winter.
Cool or fluctuating temperatures, dry air and cold draughts can cause citrus plants to drop their leaves, fail to flower or not produce fruit.
When preparing to move citrus plants outdoors for the summer, monitor overnight temperatures carefully – it may be mid-June before conditions are warm enough, depending on your local climate and the cold-tolerance of your specific plant. Also, take care to introduce citrus plants to outdoor conditions gradually by hardening off, so they don’t suffer damage or a check in growth.
Propagating
Citrus plants are usually slow growing and when started from seed may take seven to ten years to begin fruiting. So commercially, citrus trees are propagated by budding or grafting, as the resulting plants will start fruiting much earlier, in as little as two or three years. Both are quite skilled techniques, but well worth a try.
Another option is to take semi-ripe cuttings from an existing citrus plant. This ensures the new plants are clones of the mother plant and will produce equally good quality fruits.
Of course, a popular option is to grow citrus plants from fruit pips. This can be fun and is the easiest but also the slowest method. And bear in mind that the resulting plants may differ from the parent and their fruit may be of a lower quality.
March is the ideal month for sowing, but you can try with fresh pips at any time of year. They need a temperature of 16°C (61°F) to germinate.
Pruning and Training
Citrus plants are generally compact and slow growing, and most need only minimal pruning to keep them in good shape. However, they are often armed with sharp thorns, so take care and wear stout gloves.
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In February – thin out any overcrowded branches and remove wayward shoots that spoil the shape of the plant. Straggly or leggy plants can be cut back by up to two-thirds and the leading (tallest) branch can be reduced, to stimulate bushier growth.
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Over summer – pinch back the tips of the most vigorous shoots to encourage branching.
Citrus plants sometimes produce unwanted, fast-growing vertical shoots known as water shoots. Cut out any that sprout from the lower or middle portions of the main branches, and shorten any arising near the tips of the branches.
Be especially watchful for any shoots sprouting from below the graft point on the main stem, and remove them immediately.
Harvesting
Citrus fruits generally ripen slowly, taking nine to 12 months. Once they reach full size and develop a rich skin colour, they can either be picked or left on the tree until needed.
Problems
Citrus plants need plenty of warmth, sun and humidity to thrive, along with careful watering and regular feeding. If conditions aren’t to their liking, they may fail to flower or fruit successfully, or lose their leaves. Specific requirements vary depending on the type of fruit. If your citrus plant isn’t happy, see our guide to citrus problem solving.
Citrus plants are usually disease-free, but do check them on a regular basis for sap-feeding pests such as scale insects, mealybugs and red spider mites, especially when plants are indoors.
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