\documentclass[margin=5mm]{standalone}
\usepackage[ngerman]{babel}
\usepackage{tikz}
\usetikzlibrary{trees}
%\usetikzlibrary{trees}
\usepackage{amsmath, amssymb}
%===========
\begin{document}
%===========
\begin{tikzpicture}
[every node/.style={draw, circle},
%Optional
nodes={execute at begin node=$, execute at end node=$},%all nodes=''math''
font=\footnotesize,
grow=up, %Zeichenrichtung
%level 1/.style={sibling distance=9cm},
level 2/.style={sibling distance=2cm},
level distance=1cm]
\node[fill=red!40](START) {*} %nodes benennen, so spätere Beschriftung einfacher
child{ node (A) {A}
child {node (B) {B}}
child {node (C) {C}}
child {node (D)[fill=orange] {D}
child {node (E1) {E_1}}
child {node[dashed] (E2) {E_2}}
}
};
%Beschriftung
\path (START) -- (A) node [draw=none, midway, right] {\text{Hier geht's los!}};
\path (B) -- (C) node [draw=none, midway] {\text{Text}};
\path (START) -- (E2) node [draw=none, near end, left=2em] {\tiny \text{obwohl kein Ast}};
\draw[->, >=latex, very thick] (D) -- (A) node [draw=none, left=2em] {\text{Hier mal anders}};
\end{tikzpicture}
%===========
\end{document}
%===========
