Shade Trees: From Sketch to Painting?

Recently I went to nearby Cylburn Arboretum to see what I might paint for a benefit I am participating in this fall.  In spring there are paths lined with pink and white magnolias, a field of sunny daffodils, a walkway lined with dark green cypress and golden forsythia, and an orchard of cherry trees that scatter their petals at the first rain.   In early summer there are peonies and later on roses.  

This time I was surrounded by a sea of green.  I remember an art teacher once saying how difficult it was to paint in summer when there was little contrast except for the vast range of green.  Already it was hot and humid by 9:30 in the morning.  I sought out paths that led into the woods where it might be cooler.  So many paths were blocked and off limits because of fallen trees.  We have had a couple of storms this year that wrought havoc, downing trees hundreds of years old.

I turned away and found this path with wonderfully contorted tree branches that grew down to the ground and then reached up again to the sky.  As I sketched and painted, I tried to figure out how to depict the dense foliage where it seemed I could see every leaf. I knew I need only convey the sensation of leafiness, coolness, green.  I thought about Vincent Van Gogh's amazing pen and ink drawings composed of a myriad of strokes.  He made it look so simple and easy!

I wonder whether I can create a more finished painting from this watercolor?  Does the scene hold enough interest? Does the composition work?  How would I handle a larger painting?  Should it be in watercolor or oil?  What do you think?