Over the Easter holiday we met family in the Lake District and based ourselves at Helvellyn Youth Hostel. The plan was for our children to conquer Helvellyn, but Storm Kathleen laid waste to these plans.

Opting for a low level, but still very windy, walk along the shores of Ullswater gave me the chance to take in a landscape that has inspired famous painters over the years. Forming part of the Ullswater Way Heritage Trail, there is an artists’ seat upon the track that celebrates JMW Turner, John Glover and Ann Macbeth. It is interesting to reflect on how tourism has changed over the years. If you are unfamiliar with the work of each artist, upon the spot where they once sat, you can now scan a QR code with your phone and view the artists’ interpretation of the scene sketched in tranquillity and free from the burdens of modern technology.

As we took in the view, someone asked, “Is this mistletoe growing upon the tree?” “No, it’s witches’ broom,” I replied. I get asked this question from time to time and the look given to my reply is always quizzical. Looking like a bird’s nest or squirrel dray, witches’ broom is a gall that can be formed by a fungus, virus, bacteria or insects.

Birch trees are often show signs of witches’ broom and, back home, I have to look no further than a local roundabout for great examples. On birch, the commonest cause of witches’ broom in the UK is the fungus Taphrina betulina. The gall starts as a densely packed cluster of buds that eventually burst out with tree growth in all directions to create the distinctive broom. This is unlike mistletoe, which is a parasitic plant that saps nutrients from its host. In spring, microscopic sacs form upon the leaves of the broom from which the fungus will spore.

Prior to greater scientific understanding, you can picture how stories of witches leaving brooms or even sleeping within the trees develop. There is plenty of room on the broom too, with larger examples a meter or so in diameter. A tree will continue to grow just fine with witches’ broom, although some gardeners may chose to remove them for aesthetic reasons.

Upon returning to the Youth Hostel, through my phone and the links from the QR codes, I browsed the paintings of the landscape we had explored. Studying the trees within each painting, I could not make out any witches’ broom. Perhaps artistic license removed them from the scene in need of the perfect painting.

wharfedale-nats.org.uk