Citrus will thrive in UK conditions given adequate sunlight, regular feeding, and some protection from very severe weather. The biggest threats to their wellbeing are over-watering and being considered a house plant which they most certainly are not!
After having received your plant unpack immediately and place in a sunny spot, sheltered from very cold winds and temperatures which regularly go below +4°C. When the tree has acclimatised to UK conditions (usually one complete year) it will withstand lower temperatures. Your tree will not need potting on for at least the first year.
This is the most important part of citrus care. Watering should be kept to a minimum in the winter, with the soil being almost, but not completely dry. During very wet spells of winter weather, it is worth considering wrapping a layer of cling film over the soil to prevent it from becoming too wet. As spring starts, so does the increase in watering, with the amount per week in mid-summer being at about 5 litres per week for a 15 litre potted tree. Additional rain will obviously affect this and an adjustment should be made. Should flagging of the leaves occur, then additional watering may be given. If the leaf starts to take on a yellow hue, then it is most likely that the compost is too wet.
The feeding of citrus trees grown in pots is very important but must not be carried out during the winter months when root growth has ceased. Proprietary branded citrus feed can be used, but any slow-release pelleted fertiliser suitable for trees and shrubs is a very good substitute. We recommend that you apply a small handful of pelleted fertiliser every 8 weeks throughout the Spring, Summer and early Autumn and cease feeding from mid to late October onwards. Do not apply fertiliser to the tree if the temperature drops to a maximum of +8°C during daylight hours.
During the first year no pruning will be necessary other than removing damaged branches. In subsequent years pruning should be carried out, reducing the previous year’s growth by about one third. This will maintain the tree in a good, rounded shape and allow fruit buds to form.
Although citrus can easily withstand a temperature of -4°C for short periods, the combination of wet soil and low temperature will be very detrimental to them. If a suitable unheated glass house or well-lit shed is available, then this should be used but only after mid November at the earliest, and only until mid March. The tree should be brought out into the open air once the temperature reaches above +5°C regularly. Large frost protection plant jackets manufactured from 70g/m² microfleece can also be used - these are very good as they let in almost 80% of the available sunlight and will protect against rain too. If using lighter weight fleece jackets (35g/m²) we recommend covering each tree with two bags to provide a double layer of protection.
Citrus are NOT HOUSE PLANTS and will quickly defoliate in a centrally heated environment. If there is no alternative in very cold weather but to bring them into the house, then place them in a shower room or bathroom where there is a moist atmosphere. As soon as the temperature rises to above freezing then place outside once again. Remember that citrus can never have enough sunshine.
Your tree will not need potting on for at least the first year. After that time we suggest that a pot 25-30cm (10-12in) in diameter is chosen. It should have very good drainage holes and a 7cm (3in) thick layer of shells or crocks should cover the base. A loam based compost is best (John Innes No. 3), and to that should be added one quarter grit and stone. Re-potting should be carried out between mid-March and mid-April. Do NOT use a multi-purpose peat-based compost for citrus.
Pests & Diseases
Generally, if citrus trees spend the vast majority of their time outside in the sun and air then they are usually very free from pest and disease. Like most plants the young growths can become infected with green aphid during the early growing season but that is very easily controlled by either using a pesticide or by washing the leaf with water from a strong spray nozzle. Citrus Scale can be a problem, but once again, ensuring that the plants are outside in the air for as much time as cold temperatures allow keeps the scale to a bare minimum. If it is seen, then it can be simply removed by hand. Disease tends to be confined to root rotting from phytophthora due to over watering, especially in the winter months. Take what precautions you can to prevent the soil becoming overly wet.
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