Dear Sibe,

I would be most grateful if you could help me. I have purchased a mandarin and a lemon tree, both of which seem to have some sort of problem with their leaves - they are turning yellow and then falling off. I have them both planted in ericaceous soil in terracotta pots. They are in full sun during the day and well watered every night. Could you please tell me what I am doing wrong?

Many thanks,

Perry Noon.

Our Gardening Expert replies:

Hello Perry,

Citrus plants can react in this sort of way (i.e. by losing their leaves) when they have been subject to an environmental shock of some kind. You say you have them both planted in terracotta pots in ericaceous compost which is quite correct, but the shock caused to the roots when transplanting may have caused this reaction. If you removed much of the old compost before placing the plants in new compost, you could have damaged many of the roots, resulting in them being unable to take up moisture until they have re-grown.

Great care should be taken when repotting citrus plants and it is best not to disturb the rootball too much. This is achieved by adding new compost above and below the rootball where necessary.

Citrus plants are also very sensitive to the light and will react to being moved from a shady position to one where they are exposed to full sun. You can help them to recover by keeping them in a shady place until you are sure they have started to re-grow and by spraying the foliage with clean water a couple of times a day. Spraying the leaves occasionally is a good idea in any event as it helps to reduce attacks of Red Spider Mite.

Keep your plants out of direct sun until they have become accustomed to their new situations. Be careful with the watering - in a more shady position you need only keep the rootball moist and do not over water as this will prevent the roots from re-growing quickly. Once they have settled down, by all means put them in a sunnier place but introduce them to this gradually.

All the best,

Sibe.

P.S Exotic Garden has more ideas and inspiration on plants that will help you turn your back garden into a truly tropical paradise.

The picture shows a lemon tree available from Crocus.