no biggie.
i've already tried a bunch of css stuff, but ended up modifying the code in TreeViewAdapter.vb:
Private Function IsExpandable(ByVal item As TreeNode) As Boolean
Dim tv As TreeView = CType(Control, TreeView)
Return (HasChildren(item) OrElse ((Not IsNothing(item)) AndAlso item.PopulateOnDemand)) And tv.ShowExpandCollapse
End Functiondunno if it's valid in the whole scheme of things, but it works for me - just sucks to have to keep track of and re-do it on new version of the adapters.