My acanthus spinosa has some sort of leaf mould. It looks as though someone has sprinked a greyish talcum powder on to the leaves. One of the plants is about to flower so can’t be too unhealthy; but another doesn’t look so good. What do you recommend?
Acanthus, or bear’s breeches, as it is also known, is very prone to mildew, which is a greyish fungal covering of the leaves. This is common when the plant grows in a dry spot. Move it to a less dry place in late autumn. Watering and mulching might help but perhaps too much trouble. Spraying is not effective.