A number of excellent packages and other tools have been developed which make drawing trees one of the easier tasks in LaTeX. Several are described here
Abstract Drawing trees and figures in the subject Graph Theory (Mathematics) is a
requirement for researchers and teachers. This include loops, arcs, nodes,
weights for edges. This article aims to get started with PSTricks by keeping
two commands in mind viz. pstree and psmatrix with their most useful
options with the help of which a reader can draw neat tree diagrams, loops,
can label nodes, add weights to edges. After completing the diagram, one
can add these diagrams to TEX file. So working knowledge about drawing
figures in graph theory can be gained.