Anne Brueggemann-Klein introduced me to TeX macros in the joint work that we carried out on trees display. It led to a package called treetex.sty for use with LaTeX and a report about the package and how it is used.
More recently, Luo Tong and I designed a tree compiler TreeDraw that takes the same marked up logical description of a tree and compiles it into PostScript. In addition, it is an extension of treetex.sty in that it allows multiway trees rather than trees with just unary and binary nodes. And it also allows all external nodes to be drawn on a conceptual horizontal line as we do when we draw syntax trees. The PostScript output is compatible with the drawing package idraw so in principle you can modify a drawing with idraw.
Although, we have made the TreeDraw software available, we cannot maintain it. User beware! Note that TreeDraw is written in C and the package comes in gzipped, tarred form.