Problems with acts_as_tree

I have a class called Organization that is organized as a tree
(organizations have parent organizations) using a parent_id column and
an organizations_count column.

I used the generate scaffold method to create the controller and views.
But when I go to add or update an Organization, there is no select box
to select the parent Organization. I am surprised that the scaffold
generator doesn’t take care of this.

Am I doing something wrong? Or do I have to add this functionality
myself? And if the latter, what’s the best way to do it?

Thanks!

Chas. Munat
Seattle