TikZ trees grow right typesets things "upside down"

Question

This is a pretty minor gripe with what is a great library.

\documentclass[border=3em]{standalone}
\usepackage{tikz}
\usetikzlibrary{trees}
\begin{document}
\begin{tikzpicture}[grow=right]
  \node {a}
    child {
      node {b}
    }
    child{
      node {c}
    };
\end{tikzpicture}
\end{document}

This MWE produces the following output:

Note that despite the b node being written before the c node, it is the c node that is on top. This is unintuitive. I'd have expected the b node to be on top, since it's defined first.

I understand why it works that way because without the grow=right option, things are typeset in the obvious order. What I want to know is:

Is there an easy way to have right-growing trees set their nodes in the order you'd expect from reading the source?

---

Edit

Matthew's suggestion in the comments works well for basic trees. Unfortunately, it breaks the sloped option:

\documentclass[border=3em]{standalone}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
\begin{tikzpicture}[grow=right,yscale=-1,sloped]
  \node {a}
    child {
      node {b}
      edge from parent
      node[above] {Foo}
    }
    child{
      node {c}
    };
\end{tikzpicture}
\end{tikzpicture}
\end{document}

Answer 1

You simply can use the grow' option instead: (pgfmanual v2.10, p.219)

This key has the same effect as grow, only the children are arranged in the opposite order.

\documentclass[border=0,png]{standalone}
\usepackage{tikz}
\usetikzlibrary{trees}
\begin{document}
\begin{tikzpicture}[grow'=right]
  \node {a}
    child {
      node {b}
    }
    child{
      node {c}
    };
\end{tikzpicture}
\end{document}