Anatomy of Oak

Anatomy of a cross-section of oak

Cross section of an oak tree

Growth rings

Annual rings indicating individual years growth - counting the rings gives the age of the tree - wider the ring = better the season's growth - indication of seasonal weather patterns. Lighter colour within an annual ring formed in spring / early summer - less dense wood - full of sap Darker colour growth within late summer / autumn - denser wood - heartwood full of resin.

Moss on bark

Moss grows on sunless, damper side if trees i.e. north / east

Asymmetric growth pattern across the section

An indication that this particular tree had favourable growing conditions towards the north. This could be due to water supply - prevailing winds - soil conditions - competition from other trees - proximity from buildings. This growing pattern / profile is unusual as the south would usually be a more favourable aspect.


Narrow channel in the centre of the tree, branch etc.


Outside set of rings that transmit water and nutrients up through the tree from the roots to the leaves through tubes - obvious in this section as pore holes.


The 'dead' wood of the tree - strongest wood - 'backbone' or skeleton of the tree. Darker in colour - cells have ceased transmitting sap - being backfilled with resin through the medullary rays from the cambium. The resin filled cells then solidify the wood as heartwood.

Medullary Rays

Radial sets of cells that run from the bark inwards towards the centre - carrying resin - Much prized as lighter 'flashes' in oak furniture especially panels. These could also be lines of weakness or shakes. Wood splits along the rays.

Cambium Layer

Newest specialised growing layer inside the bark - bright green fresh wood fresh sapwood on inner side - new bark on the outer side.


Protective layer for the cambium layer. - part of the process is that as the tree grows this layer expands and splits - old and new bark layers. (Some trees even shed this old layer so as to discourage insects breaking in e.g. plane trees - in London.)


Shrinkage splits that take place during the initial drying or seasoning process. Also possible to see star or cup shakes along the circular rings.