Citrus trees such as orange, lemon, lime, grapefruit and kumquat thrive in a warm, humid climate and will not survive outside year round in the UK. The good news is that it is still possible to grow citrus fruits in the UK – you just need to make sure that they are protected in the colder months. You can protect them in the winter by bringing them indoors, though centrally-heating rooms will not be ideal, as they are too hot and dry and often lack light. An unheated conservatory or sun room is ideal – as is a polytunnel kept above around 10 degrees Celsius. If you have a citrus fruit summering outside in a sunny and sheltered spot, a polytunnel can also be a useful place to stow your tree if an unseasonable cold snap threatens.
In the UK, it is usually best to choose citrus trees that have been grafted onto a dwarf rootstock. If you do so then you will be able to grow these trees in containers, which will make them easier to move when colder weather strikes. Citrus trees are usually purchased as grafted saplings rather than grown from the pips. Do not be tempted to try sowing pips from fruit you have bought at the shop as these are usually from hybrid types and are unlikely to provide any edible fruits. Choose hardier varieties and take advice on the best ones for your area.
Citrus trees are hungry plants and will benefit from a high nitrogen organic feed throughout the summer months. There is no need to feed the plants between October and late March. Do make sure that you keep the trees watered (ideally with rainwater) throughout the year, however. In summer, water well and freely, especially in warmer weather. In winter, allow the surface to partially dry out before watering with tepid rainwater allowing all excess to drain away. Be careful not to overwater in winter and if in doubt, err on the drier side.
To ensure pollination and provide the right humidity, mist the trees regularly throughout the winter and ensure good ventilation whilst retaining enough heat. Re-pot or pot up every two or three years in early spring, though citrus trees like to be tight in the pot so do not choose too big a container. Choose a good loam-based compost as your growing medium.
When fully grown, the fruits will have a vibrant skin colour and will be recognisable to the eye. You may pick the fruits as and when you require them. You can also 'store' the fruits by simply leaving them on the tree until you want them. From a 1m tall citrus tree you should expect no more than 10-20 fruits.
