When I went to north Cardiff last week to see the Waxwings, I also had a walk around nearby Heath Park and found one of the best examples I’ve ever seen locally of Witch’s (or Witches’) broom. One tall Birch tree had a particularly large ‘broom’, a dense twisted mass of twigs and small branches, and several smaller ones just beginning to form.

Witch’s brooms can be found on several different tree species and, according to an entry on the Woodland Trust website, they are likely caused ‘by fungal, viral or bacterial activity, and occasionally insect activity’. However, it is generally agreed that brooms on Birch trees are caused by the fungus, Taphrina betulina.