No way to clear tree selection?

[Stefan Bley]

I can set the selected tree node through tree's "selected" attribute. But how can I clear this selection?

I tried tree1.setSelected(null) as well as tree1.setSelected("") but neither worked. The previously selected node remained selected.
I'm also wondering why a tree node is selected after deployment (last one? or the one selected in visual editor?) although i did not specify a node to be initially selected.

Stevy