As I was trimming the hawthorn at the end of the garden this morning, I found this gall on a stem growing in the top of the hedge. I think that it’s a species of rust fungus, so the tufts are the spore-producing bodies.
It looks as if the stem might have been bent over and damaged along one side, allowing the fungus to penetrate the periderm: the corky outer layer of the stem.
