I came across this special oak Quercus robur while walking with my family deep within a Berkshire woodland. It may be a furniture maker’s nightmare but it is an unusual example of the fantastic natural biomechanics of trees. The tree has four stems all of which have fused at least once to its neighbour, and sometimes many times. This is a natural form of grafting.
When pressed together branches, and even roots, will fuse together to form a natural graft union. This can happen within the same tree, as in this case, or even between different trees of the same species. It used to be thought that this was impossible due to movement of the different branches with the wind but as this photograph illustrates, it can happen given the right conditions. Normally such grafting is due to high pressure, for example one branch leaning on another, but this example is unusual because the limbs seem almost attracted to one another, seemingly without gravity being a major factor.
Why is the tree a furniture maker’s nightmare? For a start there are few straight lengths that could be run through a saw to create workable lengths of timber. Also a hidden feature in this wood will be a very high proportion of reaction wood:- the special wood that a tree produces to straighten and support itself. Generally conifers push using ‘compression’ wood, while hardwoods pull using ‘tension’ wood. So, this oak will have a very high proportion of tension wood with high lignin content making it dense and hard but weak and brittle.
Let’s hope that is outlives the Scots Pine and Silver Birch that surrounds it in this hidden valley, where it can continue to delight and enthrall the woodland explorer.