Every natural form has it's own unique aesthetic logic existing behind the chaos of its appearance. In the image above I took a messy branch from an oak tree and distilled the basic elements so that, once understood, I could redraw them with clarity from imagination using the same logic of the original but in a new arrangement (the double ended branch below).
I looked for the basic overall shape of each leaf before worrying about the details of each leaf. I looked for the overall corkscrew-like arrangement of the stems on the branch before drawing each stem. The logic is the underlying rhythm repeated through some natural form. It is best understood by thinking it out through a sketch of the basic elements in a lighter tone (graphite in the photo above) and then adding the clarifying edges and details with a darker medium (I used a rapidograph pen in the above example).