Have a 12' Japanese Maple, a wedding gift we planted 30 months ago,
which we want to move from our old to our new home.

Your experience in moving trees, and perhaps a referral to a qualified
expert in the Portland area, would be appreciated.

I'm not in the Portland area, but FWIW....

To properly relocate a tree, you must dig around the tree and build a root
ball (size varies on tree size of course). This will weigh a pretty hefty
amount naturally. Also, when moving it you will want to shield it from
the wind.

For a tree that is 12' tall I'd recommend using a professional if you can
afford to do so. That way, not only do THEY do the work but your tree will
get there safe and sound.

James