Pattern of a Tree Limb

Tree Limb Observational Sketch

On a walk through the forest preserve today, I thought about the growth of tree branches.  Seeing so many that had fallen to the ground, I wondered about their structural integrity.  Upon further reflection, I think the downed limbs had more to do with flood damage to the roots than to any defect in the branches themselves.  But, it got me thinking about how a branch grows out from a tree and sends out leaves. 

Tree limbs tend to grow and send out leaves and branches in a spiral pattern to maximize exposure to sunlight.    I found areas of the limb where it looked like the limb was going to grow in one direction, but then made a sharp turn.  I am hypothesizing that the initial direction became damaged or did not get as much sunlight as its offshoot branches and was abandoned in favor of the more productive branch. 
More observations about patterns:

• Each branch and leaf stem reaches out at approximately a 60 degree angle.  
• Thorns on this tree seem to grow in the location of, but in lieu of, branches with leaves.  

• The ratio of the secondary branch to the primary limb remains constant in that the limb is approximately 2-3x larger in diameter than the branch.   

More observations about patterns:

• Each branch and leaf stem reaches out at approximately a 60 degree angle.  

• Thorns on this tree seem to grow in the location of, but in lieu of, branches with leaves.  

• The ratio of the secondary branch to the primary limb remains constant in that the limb is approximately 2-3x larger in diameter than the branch.