How to grow citrus fruit

Some citrus plants may be available in larger garden centres, especially in summer, but for the widest choice, go to specialist online suppliers. 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. 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 in flower and/or fruiting.

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 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 – overpotting into a much bigger pot can cause problems.

Once roots start to appear through the holes in the base, it’s time to move the plant into a slightly larger pot. Do this in spring, and use either a specially formulated peat-free 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 drainage. Watch our quick video guides below to see how it’s done. 

In summer, water citrus plants freely, ideally with rainwater. The compost can dry out quickly, especially in hot weather, so check it daily. 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.

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. Misting plants may beneficial too – in summer, do it early in the morning to avoid scorching. 

Citrus are hungry plants and should be fed all year round. Lack of nutrients can cause leaves to turn yellow or drop off, and prevent flowers or fruit forming. Use fertiliser specifically formulated for citrus fruit. From Iate March to October, apply summer citrus feed, which is high in nitrogen. Then from November to mid-March, switch to a more balanced winter citrus feed. It’s also beneficial to remove the top 5cm (2in) of old potting compost annually in late spring and replace it with fresh compost.

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.

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 help the rest 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. Only kumquats, with their much smaller fruits and bushy style of growth, can successfully carry a heavy crop without any need for thinning.

As citrus plants aren’t hardy, they must be brought indoors as soon as night temperatures start to dip in autumn. Different types of citrus have different levels of tolerance to cold, so check your plant’s requirements when deciding where to keep it over winter. 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 flower in late winter. Cool or fluctuating temperatures, dry air and cold draughts can cause them 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 – you may have to wait until 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.

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 start fruiting much earlier, in two or three years. Both are quite skilled techniques, but 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 parent plant and will produce equally good quality fruits.

Still, it can be fun to grow citrus plants from fruit pips. But bear in mind that the resulting plants may take many years to produce fruit and it may be of lower quality than the original fruit. 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.