ASK DIARMUID

Q

My Aster amellus is really looking unwell. Each year it normally flowers by October but it started to suffer in the August heatwave, although I did keep it watered. Can I return it to health and, hopefully, flowering?

Fiona

A

That looks like a case of powdery mildew, a fungus that asters are prone to, especially in drought conditions. Cut all the stems back now and dispose of all the infected material in the bin. It will regrow but it’s probably too late to get sufficient growth for flowering this year.

You did the right thing keeping it watered and you were unlucky as Aster amellus is one of the more mildew resistant varieties.

If it happens next year, spray the plants with a solution of a tablespoon of baking powder and a teaspoon of washing up liquid in a gallon of water. If the problem is bad again next year, I would replace it with a different aster such as ‘Little Carlow’ or ‘Twilight’ which are also both known to be mildew resistant.