page_title: Tree fork
section_title: Bark inclusions and fork strength
hierarchical_section_title: Tree fork / Bark inclusions and fork strength
caption_attribution_description: English: An included bark junction formed in a wild cherry tree (Prunus avium)
context_page_description: A tree fork is a bifurcation in the trunk of a tree giving rise to two roughly equal diameter branches. These forks are a common feature of tree crowns. The wood grain orientation at the top of a tree fork is such that the wood's grain pattern most often interlocks to provide sufficient mechanical support. A common "malformation" of a tree fork is where bark has formed within the join, often caused by natural bracing occurring higher up in the crown of the tree, and these bark-included junctions often have a heightened risk of failure, especially when bracing branches are pruned out or are shaded out from the tree's crown.
context_section_description: Where a junction forms in a tree and bark is incorporated into the join, this is referred to as an 'included bark junction' or 'bark inclusion'.  A common cause of bark being incorporated into the junction is that the junction is braced by the touching of branches or stems set above that junction (in arboriculture, these branch interactions are termed 'natural braces'). Such included bark junctions can be substantially weaker in strength than normal tree forks, and can become a significant hazard in a tree, particularly when the bracing branches are shaded out or pruned out of the tree.  Research has shown that in hazel trees, the more the included bark is occluded within new wood growth, the stronger that junction will be, with the weakest forks being those with a large amount of unoccluded bark at their apex. Common tree care practices are to prune out such bark-included forks at an early stage of the tree's development, to brace the two arising branches above such a junction so that they can not split apart (using a flexible brace) or to reduce the length of the smaller arising branch, so that it is subordinated to the larger branch.  Care should be taken not to prune out 'natural braces' set above weak tree forks in mature trees unless that is absolutely necessary.
  The strength of a normally-formed tree fork can be assessed by its shape and the presence and location of axillary wood: those that are more U-shaped are typically considerably stronger than those that are V-shaped at their apex.  This characteristic, and the presence of bark included in a tree fork, are important attributes for tree surveyors and tree contractors to note in order to assess whether the tree fork is a defect in the structure of a tree.
caption: An included bark junction formed in a wild cherry tree (Prunus avium)
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