You will learn to paint trees only by understanding them, their growth, their nature, their movement - and realizing that they are conscious living things. A tree seldom if ever encroaches upon the liberty of another tree. It never wastes its growth in unnecessary twistings.
This art of conservation is strength, and makes the masterpiece a masterpiece. Otherwise, the man who simply brought all the different colors obtainable, and squeezed them out upon the canvas to give it 'full force,' would be the greatest master, instead of being merely extravagant.