QWhat has happened to the leaves on my grapevine?
Chris Nower, via email
AI suspect that your vine it is suffering from oedema, also known as dropsy or intumescence.
Triggered by overwatering and high humidity, which results in cells becoming waterlogged, it causes warty lumps on leaves. It rarely affects the plant’s vigour.
The best way to overcome it is to water less and increase ventilation.
Oedema causes leaves to develop strange growths