Setting up new domain tree in active directory- should tree show up in users and computers mmc?

I have set up a new tree in our domain for testing and things don't look like I expected
them to, I hope you can help..

In the AD users and computers I have my domain listed followed by the OU's
+mydomain.com
   computers
   users
   dc's
   etc..

What I was expecting to see was something like:
+mydomain.com
   computers
   users
   dc's
   etc..
   +tree1.mydomain.com
      computers
       users
       etc

I see no reference to the new tree, However if I run the domains and trusts
mmc I do see the master domain and the tree like the 2nd example. If I then select
the tree and run  manage then this takes me to the users and computers snap in
 on the sub-tree.

If managing multiple trees in a forrest is it normal to create seperate OU's at the top level
for the tree domains ( names can't match becuse objects would then be duplicated) or should the
tree show up in the root users and computers mmc.


Thanks for any help on this!

Ray