GARDEN GURU

Q

I have an old azalea in a pot with leaves covered in a powdery white growth. What is it and how do I cure it? Stephanie Barnett

A

The azalea in the photo you sent to me is infected by powdery mildew, a common fungal disease that tends to prosper when there is high humidity and the conditions around the roots are dry. I would suggest spraying the foliage with RHS Bug & Mildew Control. Going forwards, water the plant on a regular basis and remove a few internal branches to improve airflow.

Q

I have a shrub that produces scented white flowers every June. What is its name and can I take cuttings from it?

Simon Luke

A

Your shrub is Philadelphus

‘Belle Etoile’ and you can propagate it by taking cuttings in early summer. I think the lanky,

mature plant in your photo could do with pruning – cut back shoots to strong new growth and remove a quarter of older stems.

Q

We usually have success with courgettes, but for the past two years our plants failed to grow properly. Any idea why? Martyn Golesworthy

A

I’m afraid your courgette plants have cucumber mosaic virus, which causes yellowing and distortion to leaves of courgettes, marrows and other related veg. It’s usually spread by aphids, who may have picked it up from nearby weeds. Destroy the courgette plants, and keep your patch weed free. Try growing a disease-resistant variety, such as ‘Defender’ or ‘Zelia’.