Your gardening questions answered

Guy Barter, Head of Horticultural Advice at the Royal Horticultural Society, answers key questions on how to solve problems in your garden
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Olive tree
If you've had your olive tree for three years, it's worth replanting it into the next size pot
Question: I've had my olive tree for the last three years. It is planted in a pot in my garden, and until recently, was thriving quite happily. However in the last couple of weeks I have noticed that the leaves are all covered in black spots. Can you advise me what's happened to it and if anything can be done?

Answer: If the leaves on your olive are falling prematurely, then the spots are most likely to have been caused by a fungus. It is quite a common problem.

You can try using a fungicide designed for ornamental plants, or if you garden organically, then try moving your plant into a very sunny position and thin out the foliage so the air can circulate, which helps to reduce the risk of fungus. Always remember to collect the infected leaves and bin them (don't compost them as they could infect your compost).

Also, if you've had your tree for three years, it's worth replanting it into the next size pot, using John Innes No 3 compost.

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