These settings are available after the Q1 2013 SP1 release of the Telerik controls.
You can take advantage of the additional functionality that we implemented with the RadDropDownTree control by using the DropDownSettings:
AutoWidth - enlarges and shrinks the width of the dropdown when nodes are expanded and collapsed respectively;
OpenDropDownOnLoad - opens the dropdown when the page is loaded;
CloseDropDownOnSelection - this property is added since Q1 2014 -it closes the dropdown automatically when a new entry is selected;
CssClass - sets a custom css class that enables the used to alter the appearance of the dropdown.