Q&A Plants: Rose mildew

My climbing rose suffered badly from powdery mildew for the first time last year. What can I do?

Liz Dobbs: Powdery mildew, seen as a white dust over foliage, tends to take hold when plants are short of water and where airflow is poor, so climbers growing against walls are particularly vulnerable. You can help prevent it by training the roses in such a way that air can circulate around them -trellis and pergolas provide more open structures. Careful training and pruning, so there aren't overlapping branches or too much overcrowding, will also help.

Water well in dry spells, and mulch in spring or autumn. Mildew can weaken roses, and ruin their appearance, but it is unlikely to kill them. Rose mildew tends to be worse in dry summers like the one we have just had.