“Beneath you birch with silver bark
And boughs so pendulous and fair”Samuel Taylor Coleridge
Ancient birch trees have the most wonderful body language in old age. Their trunks and lower horizontal limbs are no longer just round, but become deeply fissured and even rope-like.
The development of such discrete columns of living wood, called functional units, is a strategy for survival. They can be regarded as separate trees, each of which can transport carbohydrates from photosynthesis from the crown down the tree and water and nutrients up from the roots. In some uncommon situations a functional unit can stand alone or break free from the original tree – allowing at least part of the tree to carry on living independently.