AW.UI.Tree - Clearing the nodes

Can someone out there lend a hand?

I'm using a AW.UI.Tree control to dynamically show the directories of a machine. I've added a combo box to allow me to change the root folder that is displayed in the tree. However, I am unable to clear the previous contents of the tree successfully. Does anyone know the methods that need to be called to clear out all the nodes of a tree?

Thanks.