There are a few things you need to know before starting to make trees in Illustrator. First, you will need to create a tree object. This object will be used to create the tree’s branches and leaves. Next, you will need to create the root of the tree. The root should be created as a dashed line and its length should be set to 1px. Finally, you will need to create the leaves of the tree. The leaves should be created as rectangles and their length should be set to 1px as well.