Or can this only be done programmatically/
<
telerik:RadTreeView x:Name="tvThemes" Background="#00CA4141"
IsExpandOnSingleClickEnabled ="True"
IsTriStateMode="True"
IsOptionElementsEnabled="True"
ItemsOptionListType="CheckList"
IsEditable="true"
>
<telerik:RadTreeView.ItemTemplate>
<telerikCore:HierarchicalDataTemplate ItemsSource="{Binding Themes}" >
<TextBlock Text="{Binding Title}" />
</telerikCore:HierarchicalDataTemplate>
</telerik:RadTreeView.ItemTemplate>
</telerik:RadTreeView>