Witches Brooms

A little late for Hallowe'en I know, but I was impressed by the witches' brooms growing in this birch tree in Silverknowes. Now the leaves have mostly fallen the brooms are more noticeable than they usually are.

The witches broom is a growth caused by pests  or disease, for example wasps, viruses or fungi. Although they occur in a number of different species of tree, in this country at least they are most obvious in birch trees.