There are two layers in this drawing. The first layer is the tree trunk and brunches drawn as a single curve with a series of points. The second layer consists of clumps of leaves positioned on the branches and at the bottom of the tree.
This is one of the clumps of leaves I used in the second layer. Each leaf is drawn separately and then grouped together with a small twig, shrunk and placed on the branches.
This is the clump of leaves I used at the bottom of the tree.