How to specify left and right node of a tikz-qtree

Question

I'm drawing a binary tree using tikz-qtree. In my binary tree the order of children is important, so I need distinguish which edge is the left one and the right one. In my sample code I can't distinguish if the node 1 is left or right. There is a way to specify this?

\documentclass[demo]{article}
\usepackage{tikz,tikz-qtree}
\begin{document}
\begin{figure}[ht]\begin{center}\begin{tikzpicture}[grow'=up]
\Tree [.\node(8){8}; 
       [.\node(5){5}; 
              [.\node(3){3}; 
                 \node(1){1}; ]
                \node(6){6}; ] 
             \node(12){12}; ]
\end{tikzpicture}\end{center}\end{figure}
\end{document}

Answer 1

You can specify edges explicitly when needed, and specify [draw=none]. I've also simplified your tree: you don't need to enclose every node in a \node command unless you have independent reasons for referring to them. For this kind of tree, it might be helpful to make every node a uniform size, so that the sibling distances don't vary. You can do this by setting a minimum size for the every tree node/.style. I've given a second tree showing how this can be done. In a single tree, you could add the option to the {tikzpicture} environment itself instead of using \tikzset.

\documentclass{article}
\usepackage{tikz-qtree}
\begin{document}
\begin{tikzpicture}[grow'=up]
\Tree [.8 
        [.5 
            [.3 
                \edge[]; {1}
                \edge[draw=none]; {}  ]
             6  ] 
          12 ]
\begin{scope}[xshift=2in]
\tikzset{every tree node/.style={minimum width=2em}}
\Tree [.8 
        [.5 
            [.3 
                \edge[]; {1}
                \edge[draw=none]; {}  ]
             6  ] 
          12 ]
\end{scope}   
\end{tikzpicture}
\end{document}