In reality a group of leaves arises from one of the arms of the tree. The groups lie in front and behind each other because a tree is not a flat thing. Here’s a way to learn how to draw a tree with large groups of leaves in five steps:
Exercise 1:
Draw each step before moving on to the next step.
Step 1: above the trunk you draw as lightly as possible circles right through each other. The circles don’t have to be perfect! Each circle represents one group of leaves.
Step 3: now choose in the other circles (groups of leaves) which are in front and which are behind. Each time erase the lines of the underlying circle.
Step 5: draw more leaves in each group. Let them point in different directions.
In Exercise 1 I started with circles as basic shapes but different types of trees may of course have other basic shapes. Later you can make those basic shapes leaf-like again. In this way you can even make a real Christmas tree (the bottom two).
Exercise 2: draw as lightly as possible the following models of trees. If you want to make the basic shapes more leaf-like, it is useful to view some photos of the type of tree. In a weeping willow, for example, the leaves point downwards like tears. Color the tree as you like.
Christmas tree