The very top of this tree has a Witch’s Broom. In this type of deformity, the natural structure of the tree is changed by having a dense mass of shoots growing from a single point. The resulting structure resembles a broom or a bird’s nest.
Caused by fungus, mites, nematodes, viruses or bacteria, brooms are a rich source of new cultivars when parts are collected and later grafted. This is because the attacking organism can sometimes actually change the inherited growth pattern of the twigs. Brooms thus provide the genetic source for many landscape plants sold at nurseries.
The amazing species (T. canadensis) is incredibly long-lived and can reach 1,000 years.