I have this tree:

```
\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{trees}

\begin{document}
\begin{tikzpicture}
  \node[circle, draw] (2) {2}
    child[edge from parent fork down] { node[circle, draw] (3) {3}
      child { node[circle, draw] (4) {4}
        child { node[circle, draw] (5) {5}
          child { node[circle, draw] (16) {16} }
          child { node[circle, draw] (9) {9} }
        }
        child { node[circle, draw] (7) {7}
          child { node[circle, draw] (11) {11} }
          child { node[circle, draw] (18) {18} }
        }
      }
    };
\end{tikzpicture}
\end{document}
```

The problem is nodes 9 and 11 and written on top of each other.

![cartesian.png](/image?hash=803776dae4cc651bfc495c8a974eefbaffc2e64d0d7dd6c72a53960059b78514)

-----

Using the forest package, as suggested with:

```
\documentclass{article}
\usepackage{forest}

\begin{document}
\begin{forest}
  for tree={
    circle,
    draw,
minimum width=3em}
  [2
    [3
      [4
        [5
          [16]
          [9]
        ]
        [7
          [11]
          [18]
        ]
      ]
    ]
  ]
\end{forest}
\end{document}
```

it is much improved. But how can I get the edges from nodes 2 and 3 to go in the correct direction? Currently they point straight down.

![tmp2.png](/image?hash=4172576e3fe54cb16b9a665307e4682ba01014ac92f634d95f809a8b66cea463)