Quick QUESTIONS

What’s the white powder on my lovely Michaelmas daisies?

Gwen Bardson, by email This is powdery mildew, which is usually most severe in hot, dry summers. It can be controlled to some extent by an approved fungicide, but the real problem is that the varieties you have are prone to the disease. Try growing a variety called ‘Mönch’, which is highly resistant.

I was given a bunch of carnations for my birthday. Their stems have produced roots in the vase. Can I plant them?

Natalie Ward, by email

You may well be able to grow them on in pots of good potting compost, but they won’t succeed in the garden because the varieties of carnation grown as cut flowers are raised in warm greenhouses. If you really like them, however, you could try growing the so-called border carnations, which are perfectly hardy and will go on for years outside.

How can I stop shrews eating my sedums?

Jonny Pole, by email

Shrews won’t be the culprits as they don’t eat plant life. The problem may be voles or mice, although I’d be surprised if they eat sedums, which have very acrid sap. Check carefully, therefore, that there isn’t some other cause for the plants disappearing. I don’t believe in killing small creatures without very good reason.

Why does my Christmas rose grow well, but then turn black and die off?

Ben Watson, Facebook

The problem is a fungal disease called hellebore blight. Unfortunately, there’s no effective chemical control and all you can do is to cut off and destroy any affected foliage and give the plant a thick mulch, which will help prevent the spores being splashed up from the soil.